linux serial构架分析及驱动开发（3）
原文地址：http://blog.csdn.net/sirzjp/article/details/6164694
这一节我们将介绍一个serial驱动的实例，后面各节中也将以这个例子来分析串口各种操作的实际情景(例子是at91sam9260板子的串口驱动)。
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2、platform驱动。platform设备由platform驱动进行管理。当设备加入到系统中时，platform_driver的probe方法会被调用来见对应的设备添加或者注册到内核；当设备从系统中移除时，platform_driver的remove方法会被调用来做一些清理工作，如移除该设备的一些实例、注销一些已注册到系统中去的东西。
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更详细platform资料可参考网上相关文章。
/*
* linux/drivers/char/atmel_serial.c
*
* Driver for Atmel AT91 / AT32 Serial ports
* Copyright (C) 2003 Rick Bronson
*
* Based on drivers/char/serial_sa1100.c, by Deep Blue Solutions Ltd.
* Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
*
* DMA support added by Chip Coldwell.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <linux/module.h>
#include <linux/tty.h>
#include <linux/ioport.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/serial.h>
#include <linux/clk.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/tty_flip.h>
#include <linux/platform_device.h>
#include <linux/dma-mapping.h>
#include <linux/atmel_pdc.h>
#include <linux/atmel_serial.h>
#include <asm/io.h>
#include <asm/mach/serial_at91.h>
#include <mach/board.h>
#ifdef CONFIG_ARM
#include <mach/cpu.h>
#include <mach/gpio.h>
#endif
#define PDC_BUFFER_SIZE 512
/* Revisit: We should calculate this based on the actual port settings */
#define PDC_RX_TIMEOUT (3 * 10) /* 3 bytes */
#if defined(CONFIG_SERIAL_ATMEL_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif
#include <linux/serial_core.h>
#ifdef CONFIG_SERIAL_ATMEL_TTYAT
/* Use device name ttyAT, major 204 and minor 154-169. This is necessary if we
* should coexist with the 8250 driver, such as if we have an external 16C550
* UART. */
#define SERIAL_ATMEL_MAJOR 204
#define MINOR_START 154
#define ATMEL_DEVICENAME "ttyAT"
#else
/* Use device name ttyS, major 4, minor 64-68. This is the usual serial port
* name, but it is legally reserved for the 8250 driver. */
#define SERIAL_ATMEL_MAJOR TTY_MAJOR
#define MINOR_START 64
#define ATMEL_DEVICENAME "ttyS"
#endif
#define ATMEL_ISR_PASS_LIMIT 256
/* UART registers. CR is write-only, hence no GET macro */
#define UART_PUT_CR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_CR)
#define UART_GET_MR(port) __raw_readl((port)->membase + ATMEL_US_MR)
#define UART_PUT_MR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_MR)
#define UART_PUT_IER(port,v) __raw_writel(v, (port)->membase + ATMEL_US_IER)
#define UART_PUT_IDR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_IDR)
#define UART_GET_IMR(port) __raw_readl((port)->membase + ATMEL_US_IMR)
#define UART_GET_CSR(port) __raw_readl((port)->membase + ATMEL_US_CSR)
#define UART_GET_CHAR(port) __raw_readl((port)->membase + ATMEL_US_RHR)
#define UART_PUT_CHAR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_THR)
#define UART_GET_BRGR(port) __raw_readl((port)->membase + ATMEL_US_BRGR)
#define UART_PUT_BRGR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_BRGR)
#define UART_PUT_RTOR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_RTOR)
/* PDC registers */
#define UART_PUT_PTCR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_PTCR)
#define UART_GET_PTSR(port) __raw_readl((port)->membase + ATMEL_PDC_PTSR)
#define UART_PUT_RPR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_RPR)
#define UART_GET_RPR(port) __raw_readl((port)->membase + ATMEL_PDC_RPR)
#define UART_PUT_RCR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_RCR)
#define UART_PUT_RNPR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_RNPR)
#define UART_PUT_RNCR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_RNCR)
#define UART_PUT_TPR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_TPR)
#define UART_PUT_TCR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_TCR)
#define UART_GET_TCR(port) __raw_readl((port)->membase + ATMEL_PDC_TCR)
static int (*atmel_open_hook)(struct uart_port *);
static void (*atmel_close_hook)(struct uart_port *);
struct atmel_dma_buffer {
unsigned char *buf;
dma_addr_t dma_addr;
unsigned int dma_size;
unsigned int ofs;
};
struct atmel_uart_char {
u16 status;
u16 ch;
};
#define ATMEL_SERIAL_RINGSIZE 1024
/*
* We wrap our port structure around the generic uart_port.
*/
struct atmel_uart_port {
struct uart_port uart; /* uart */
struct clk *clk; /* uart clock */
int may_wakeup; /* cached value of device_may_wakeup for times we need to disable it */
u32 backup_imr; /* IMR saved during suspend */
int break_active; /* break being received */
short use_dma_rx; /* enable PDC receiver */
short pdc_rx_idx; /* current PDC RX buffer */
struct atmel_dma_buffer pdc_rx[2]; /* PDC receier */
short use_dma_tx; /* enable PDC transmitter */
struct atmel_dma_buffer pdc_tx; /* PDC transmitter */
struct tasklet_struct tasklet;
unsigned int irq_status;
unsigned int irq_status_prev;
struct circ_buf rx_ring;
};
static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];
#ifdef SUPPORT_SYSRQ
static struct console atmel_console;
#endif
static inline struct atmel_uart_port *
to_atmel_uart_port(struct uart_port *uart)
{
return container_of(uart, struct atmel_uart_port, uart);
}
#ifdef CONFIG_SERIAL_ATMEL_PDC
static bool atmel_use_dma_rx(struct uart_port *port)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
return atmel_port->use_dma_rx;
}
static bool atmel_use_dma_tx(struct uart_port *port)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
return atmel_port->use_dma_tx;
}
#else
static bool atmel_use_dma_rx(struct uart_port *port)
{
return false;
}
static bool atmel_use_dma_tx(struct uart_port *port)
{
return false;
}
#endif
/*
* Return TIOCSER_TEMT when transmitter FIFO and Shift register is empty.
*/
static u_int atmel_tx_empty(struct uart_port *port)
{
return (UART_GET_CSR(port) & ATMEL_US_TXEMPTY) ? TIOCSER_TEMT : 0;
}
/*
* Set state of the modem control output lines
*/
static void atmel_set_mctrl(struct uart_port *port, u_int mctrl)
{
unsigned int control = 0;
unsigned int mode;
#ifdef CONFIG_ARCH_AT91RM9200
if (cpu_is_at91rm9200()) {
/*
* AT91RM9200 Errata #39: RTS0 is not internally connected
* to PA21. We need to drive the pin manually.
*/
if (port->mapbase == AT91RM9200_BASE_US0) {
if (mctrl & TIOCM_RTS)
at91_set_gpio_value(AT91_PIN_PA21, 0);
else
at91_set_gpio_value(AT91_PIN_PA21, 1);
}
}
#endif
if (mctrl & TIOCM_RTS)
control |= ATMEL_US_RTSEN;
else
control |= ATMEL_US_RTSDIS;
if (mctrl & TIOCM_DTR)
control |= ATMEL_US_DTREN;
else
control |= ATMEL_US_DTRDIS;
UART_PUT_CR(port, control);
/* Local loopback mode? */
mode = UART_GET_MR(port) & ~ATMEL_US_CHMODE;
if (mctrl & TIOCM_LOOP)
mode |= ATMEL_US_CHMODE_LOC_LOOP;
else
mode |= ATMEL_US_CHMODE_NORMAL;
UART_PUT_MR(port, mode);
}
/*
* Get state of the modem control input lines
*/
static u_int atmel_get_mctrl(struct uart_port *port)
{
unsigned int status, ret = 0;
status = UART_GET_CSR(port);
/*
* The control signals are active low.
*/
if (!(status & ATMEL_US_DCD))
ret |= TIOCM_CD;
if (!(status & ATMEL_US_CTS))
ret |= TIOCM_CTS;
if (!(status & ATMEL_US_DSR))
ret |= TIOCM_DSR;
if (!(status & ATMEL_US_RI))
ret |= TIOCM_RI;
return ret;
}
/*
* Stop transmitting.
*/
static void atmel_stop_tx(struct uart_port *port)
{
if (atmel_use_dma_tx(port)) {
/* disable PDC transmit */
UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);
UART_PUT_IDR(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
} else
UART_PUT_IDR(port, ATMEL_US_TXRDY);
}
/*
* Start transmitting.
*/
static void atmel_start_tx(struct uart_port *port)
{
if (atmel_use_dma_tx(port)) {
if (UART_GET_PTSR(port) & ATMEL_PDC_TXTEN)
/* The transmitter is already running. Yes, we
really need this.*/
return;
UART_PUT_IER(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
/* re-enable PDC transmit */
UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
} else
UART_PUT_IER(port, ATMEL_US_TXRDY);
}
/*
* Stop receiving - port is in process of being closed.
*/
static void atmel_stop_rx(struct uart_port *port)
{
if (atmel_use_dma_rx(port)) {
/* disable PDC receive */
UART_PUT_PTCR(port, ATMEL_PDC_RXTDIS);
UART_PUT_IDR(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
} else
UART_PUT_IDR(port, ATMEL_US_RXRDY);
}
/*
* Enable modem status interrupts
*/
static void atmel_enable_ms(struct uart_port *port)
{
UART_PUT_IER(port, ATMEL_US_RIIC | ATMEL_US_DSRIC
| ATMEL_US_DCDIC | ATMEL_US_CTSIC);
}
/*
* Control the transmission of a break signal
*/
static void atmel_break_ctl(struct uart_port *port, int break_state)
{
if (break_state != 0)
UART_PUT_CR(port, ATMEL_US_STTBRK); /* start break */
else
UART_PUT_CR(port, ATMEL_US_STPBRK); /* stop break */
}
/*
* Stores the incoming character in the ring buffer
*/
static void
atmel_buffer_rx_char(struct uart_port *port, unsigned int status,
unsigned int ch)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
struct circ_buf *ring = &atmel_port->rx_ring;
struct atmel_uart_char *c;
if (!CIRC_SPACE(ring->head, ring->tail, ATMEL_SERIAL_RINGSIZE))
/* Buffer overflow, ignore char */
return;
c = &((struct atmel_uart_char *)ring->buf)[ring->head];
c->status = status;
c->ch = ch;
/* Make sure the character is stored before we update head. */
smp_wmb();
ring->head = (ring->head + 1) & (ATMEL_SERIAL_RINGSIZE - 1);
}
/*
* Deal with parity, framing and overrun errors.
*/
static void atmel_pdc_rxerr(struct uart_port *port, unsigned int status)
{
/* clear error */
UART_PUT_CR(port, ATMEL_US_RSTSTA);
if (status & ATMEL_US_RXBRK) {
/* ignore side-effect */
status &= ~(ATMEL_US_PARE | ATMEL_US_FRAME);
port->icount.brk++;
}
if (status & ATMEL_US_PARE)
port->icount.parity++;
if (status & ATMEL_US_FRAME)
port->icount.frame++;
if (status & ATMEL_US_OVRE)
port->icount.overrun++;
}
/*
* Characters received (called from interrupt handler)
*/
static void atmel_rx_chars(struct uart_port *port)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
unsigned int status, ch;
status = UART_GET_CSR(port);
while (status & ATMEL_US_RXRDY) {
ch = UART_GET_CHAR(port);
/*
* note that the error handling code is
* out of the main execution path
*/
if (unlikely(status & (ATMEL_US_PARE | ATMEL_US_FRAME
| ATMEL_US_OVRE | ATMEL_US_RXBRK)
|| atmel_port->break_active)) {
/* clear error */
UART_PUT_CR(port, ATMEL_US_RSTSTA);
if (status & ATMEL_US_RXBRK
&& !atmel_port->break_active) {
atmel_port->break_active = 1;
UART_PUT_IER(port, ATMEL_US_RXBRK);
} else {
/*
* This is either the end-of-break
* condition or we've received at
* least one character without RXBRK
* being set. In both cases, the next
* RXBRK will indicate start-of-break.
*/
UART_PUT_IDR(port, ATMEL_US_RXBRK);
status &= ~ATMEL_US_RXBRK;
atmel_port->break_active = 0;
}
}
atmel_buffer_rx_char(port, status, ch);
status = UART_GET_CSR(port);
}
tasklet_schedule(&atmel_port->tasklet);
}
/*
* Transmit characters (called from tasklet with TXRDY interrupt
* disabled)
*/
static void atmel_tx_chars(struct uart_port *port)
{
struct circ_buf *xmit = &port->info->xmit;
if (port->x_char && UART_GET_CSR(port) & ATMEL_US_TXRDY) {
UART_PUT_CHAR(port, port->x_char);
port->icount.tx++;
port->x_char = 0;
}
if (uart_circ_empty(xmit) || uart_tx_stopped(port))
return;
while (UART_GET_CSR(port) & ATMEL_US_TXRDY) {
UART_PUT_CHAR(port, xmit->buf[xmit->tail]);
xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
port->icount.tx++;
if (uart_circ_empty(xmit))
break;
}
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(port);
if (!uart_circ_empty(xmit))
UART_PUT_IER(port, ATMEL_US_TXRDY);
}
/*
* receive interrupt handler.
*/
static void
atmel_handle_receive(struct uart_port *port, unsigned int pending)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
if (atmel_use_dma_rx(port)) {
/*
* PDC receive. Just schedule the tasklet and let it
* figure out the details.
*
* TODO: We're not handling error flags correctly at
* the moment.
*/
if (pending & (ATMEL_US_ENDRX | ATMEL_US_TIMEOUT)) {
UART_PUT_IDR(port, (ATMEL_US_ENDRX
| ATMEL_US_TIMEOUT));
tasklet_schedule(&atmel_port->tasklet);
}
if (pending & (ATMEL_US_RXBRK | ATMEL_US_OVRE |
ATMEL_US_FRAME | ATMEL_US_PARE))
atmel_pdc_rxerr(port, pending);
}
/* Interrupt receive */
if (pending & ATMEL_US_RXRDY)
atmel_rx_chars(port);
else if (pending & ATMEL_US_RXBRK) {
/*
* End of break detected. If it came along with a
* character, atmel_rx_chars will handle it.
*/
UART_PUT_CR(port, ATMEL_US_RSTSTA);
UART_PUT_IDR(port, ATMEL_US_RXBRK);
atmel_port->break_active = 0;
}
}
/*
* transmit interrupt handler. (Transmit is IRQF_NODELAY safe)
*/
static void
atmel_handle_transmit(struct uart_port *port, unsigned int pending)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
if (atmel_use_dma_tx(port)) {
/* PDC transmit */
if (pending & (ATMEL_US_ENDTX | ATMEL_US_TXBUFE)) {
UART_PUT_IDR(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
tasklet_schedule(&atmel_port->tasklet);
}
} else {
/* Interrupt transmit */
if (pending & ATMEL_US_TXRDY) {
UART_PUT_IDR(port, ATMEL_US_TXRDY);
tasklet_schedule(&atmel_port->tasklet);
}
}
}
/*
* status flags interrupt handler.
*/
static void
atmel_handle_status(struct uart_port *port, unsigned int pending,
unsigned int status)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
if (pending & (ATMEL_US_RIIC | ATMEL_US_DSRIC | ATMEL_US_DCDIC
| ATMEL_US_CTSIC)) {
atmel_port->irq_status = status;
tasklet_schedule(&atmel_port->tasklet);
}
}
/*
* Interrupt handler
*/
static irqreturn_t atmel_interrupt(int irq, void *dev_id)
{
struct uart_port *port = dev_id;
unsigned int status, pending, pass_counter = 0;
do {
status = UART_GET_CSR(port);
pending = status & UART_GET_IMR(port);
if (!pending)
break;
atmel_handle_receive(port, pending);
atmel_handle_status(port, pending, status);
atmel_handle_transmit(port, pending);
} while (pass_counter++ < ATMEL_ISR_PASS_LIMIT);
return pass_counter ? IRQ_HANDLED : IRQ_NONE;
}
/*
* Called from tasklet with ENDTX and TXBUFE interrupts disabled.
*/
static void atmel_tx_dma(struct uart_port *port)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
struct circ_buf *xmit = &port->info->xmit;
struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
int count;
/* nothing left to transmit? */
if (UART_GET_TCR(port))
return;
xmit->tail += pdc->ofs;
xmit->tail &= UART_XMIT_SIZE - 1;
port->icount.tx += pdc->ofs;
pdc->ofs = 0;
/* more to transmit - setup next transfer */
/* disable PDC transmit */
UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);
if (!uart_circ_empty(xmit)) {
dma_sync_single_for_device(port->dev,
pdc->dma_addr,
pdc->dma_size,
DMA_TO_DEVICE);
count = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
pdc->ofs = count;
UART_PUT_TPR(port, pdc->dma_addr + xmit->tail);
UART_PUT_TCR(port, count);
/* re-enable PDC transmit and interrupts */
UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
UART_PUT_IER(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
}
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(port);
}
static void atmel_rx_from_ring(struct uart_port *port)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
struct circ_buf *ring = &atmel_port->rx_ring;
unsigned int flg;
unsigned int status;
while (ring->head != ring->tail) {
struct atmel_uart_char c;
/* Make sure c is loaded after head. */
smp_rmb();
c = ((struct atmel_uart_char *)ring->buf)[ring->tail];
ring->tail = (ring->tail + 1) & (ATMEL_SERIAL_RINGSIZE - 1);
port->icount.rx++;
status = c.status;
flg = TTY_NORMAL;
/*
* note that the error handling code is
* out of the main execution path
*/
if (unlikely(status & (ATMEL_US_PARE | ATMEL_US_FRAME
| ATMEL_US_OVRE | ATMEL_US_RXBRK))) {
if (status & ATMEL_US_RXBRK) {
/* ignore side-effect */
status &= ~(ATMEL_US_PARE | ATMEL_US_FRAME);
port->icount.brk++;
if (uart_handle_break(port))
continue;
}
if (status & ATMEL_US_PARE)
port->icount.parity++;
if (status & ATMEL_US_FRAME)
port->icount.frame++;
if (status & ATMEL_US_OVRE)
port->icount.overrun++;
status &= port->read_status_mask;
if (status & ATMEL_US_RXBRK)
flg = TTY_BREAK;
else if (status & ATMEL_US_PARE)
flg = TTY_PARITY;
else if (status & ATMEL_US_FRAME)
flg = TTY_FRAME;
}
if (uart_handle_sysrq_char(port, c.ch))
continue;
uart_insert_char(port, status, ATMEL_US_OVRE, c.ch, flg);
}
/*
* Drop the lock here since it might end up calling
* uart_start(), which takes the lock.
*/
spin_unlock(&port->lock);
tty_flip_buffer_push(port->info->port.tty);
spin_lock(&port->lock);
}
static void atmel_rx_from_dma(struct uart_port *port)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
struct tty_struct *tty = port->info->port.tty;
struct atmel_dma_buffer *pdc;
int rx_idx = atmel_port->pdc_rx_idx;
unsigned int head;
unsigned int tail;
unsigned int count;
do {
/* Reset the UART timeout early so that we don't miss one */
UART_PUT_CR(port, ATMEL_US_STTTO);
pdc = &atmel_port->pdc_rx[rx_idx];
head = UART_GET_RPR(port) - pdc->dma_addr;
tail = pdc->ofs;
/* If the PDC has switched buffers, RPR won't contain
* any address within the current buffer. Since head
* is unsigned, we just need a one-way comparison to
* find out.
*
* In this case, we just need to consume the entire
* buffer and resubmit it for DMA. This will clear the
* ENDRX bit as well, so that we can safely re-enable
* all interrupts below.
*/
head = min(head, pdc->dma_size);
if (likely(head != tail)) {
dma_sync_single_for_cpu(port->dev, pdc->dma_addr,
pdc->dma_size, DMA_FROM_DEVICE);
/*
* head will only wrap around when we recycle
* the DMA buffer, and when that happens, we
* explicitly set tail to 0. So head will
* always be greater than tail.
*/
count = head - tail;
tty_insert_flip_string(tty, pdc->buf + pdc->ofs, count);
dma_sync_single_for_device(port->dev, pdc->dma_addr,
pdc->dma_size, DMA_FROM_DEVICE);
port->icount.rx += count;
pdc->ofs = head;
}
/*
* If the current buffer is full, we need to check if
* the next one contains any additional data.
*/
if (head >= pdc->dma_size) {
pdc->ofs = 0;
UART_PUT_RNPR(port, pdc->dma_addr);
UART_PUT_RNCR(port, pdc->dma_size);
rx_idx = !rx_idx;
atmel_port->pdc_rx_idx = rx_idx;
}
} while (head >= pdc->dma_size);
/*
* Drop the lock here since it might end up calling
* uart_start(), which takes the lock.
*/
spin_unlock(&port->lock);
tty_flip_buffer_push(tty);
spin_lock(&port->lock);
UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
}
/*
* tasklet handling tty stuff outside the interrupt handler.
*/
static void atmel_tasklet_func(unsigned long data)
{
struct uart_port *port = (struct uart_port *)data;
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
unsigned int status;
unsigned int status_change;
/* The interrupt handler does not take the lock */
spin_lock(&port->lock);
if (atmel_use_dma_tx(port))
atmel_tx_dma(port);
else
atmel_tx_chars(port);
status = atmel_port->irq_status;
status_change = status ^ atmel_port->irq_status_prev;
if (status_change & (ATMEL_US_RI | ATMEL_US_DSR
| ATMEL_US_DCD | ATMEL_US_CTS)) {
/* TODO: All reads to CSR will clear these interrupts! */
if (status_change & ATMEL_US_RI)
port->icount.rng++;
if (status_change & ATMEL_US_DSR)
port->icount.dsr++;
if (status_change & ATMEL_US_DCD)
uart_handle_dcd_change(port, !(status & ATMEL_US_DCD));
if (status_change & ATMEL_US_CTS)
uart_handle_cts_change(port, !(status & ATMEL_US_CTS));
wake_up_interruptible(&port->info->delta_msr_wait);
atmel_port->irq_status_prev = status;
}
if (atmel_use_dma_rx(port))
atmel_rx_from_dma(port);
else
atmel_rx_from_ring(port);
spin_unlock(&port->lock);
}
/*
* Perform initialization and enable port for reception
*/
static int atmel_startup(struct uart_port *port)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
struct tty_struct *tty = port->info->port.tty;
int retval;
/*
* Ensure that no interrupts are enabled otherwise when
* request_irq() is called we could get stuck trying to
* handle an unexpected interrupt
*/
UART_PUT_IDR(port, -1);
/*
* Allocate the IRQ
*/
retval = request_irq(port->irq, atmel_interrupt, IRQF_SHARED,
tty ? tty->name : "atmel_serial", port);
if (retval) {
printk("atmel_serial: atmel_startup - Can't get irq/n");
return retval;
}
/*
* Initialize DMA (if necessary)
*/
if (atmel_use_dma_rx(port)) {
int i;
for (i = 0; i < 2; i++) {
struct atmel_dma_buffer *pdc = &atmel_port->pdc_rx[i];
pdc->buf = kmalloc(PDC_BUFFER_SIZE, GFP_KERNEL);
if (pdc->buf == NULL) {
if (i != 0) {
dma_unmap_single(port->dev,
atmel_port->pdc_rx[0].dma_addr,
PDC_BUFFER_SIZE,
DMA_FROM_DEVICE);
kfree(atmel_port->pdc_rx[0].buf);
}
free_irq(port->irq, port);
return -ENOMEM;
}
pdc->dma_addr = dma_map_single(port->dev,
pdc->buf,
PDC_BUFFER_SIZE,
DMA_FROM_DEVICE);
pdc->dma_size = PDC_BUFFER_SIZE;
pdc->ofs = 0;
}
atmel_port->pdc_rx_idx = 0;
UART_PUT_RPR(port, atmel_port->pdc_rx[0].dma_addr);
UART_PUT_RCR(port, PDC_BUFFER_SIZE);
UART_PUT_RNPR(port, atmel_port->pdc_rx[1].dma_addr);
UART_PUT_RNCR(port, PDC_BUFFER_SIZE);
}
if (atmel_use_dma_tx(port)) {
struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
struct circ_buf *xmit = &port->info->xmit;
pdc->buf = xmit->buf;
pdc->dma_addr = dma_map_single(port->dev,
pdc->buf,
UART_XMIT_SIZE,
DMA_TO_DEVICE);
pdc->dma_size = UART_XMIT_SIZE;
pdc->ofs = 0;
}
/*
* If there is a specific "open" function (to register
* control line interrupts)
*/
if (atmel_open_hook) {
retval = atmel_open_hook(port);
if (retval) {
free_irq(port->irq, port);
return retval;
}
}
/*
* Finally, enable the serial port
*/
UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
/* enable xmit & rcvr */
UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);
if (atmel_use_dma_rx(port)) {
/* set UART timeout */
UART_PUT_RTOR(port, PDC_RX_TIMEOUT);
UART_PUT_CR(port, ATMEL_US_STTTO);
UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
/* enable PDC controller */
UART_PUT_PTCR(port, ATMEL_PDC_RXTEN);
} else {
/* enable receive only */
UART_PUT_IER(port, ATMEL_US_RXRDY);
}
return 0;
}
/*
* Disable the port
*/
static void atmel_shutdown(struct uart_port *port)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
/*
* Ensure everything is stopped.
*/
atmel_stop_rx(port);
atmel_stop_tx(port);
/*
* Shut-down the DMA.
*/
if (atmel_use_dma_rx(port)) {
int i;
for (i = 0; i < 2; i++) {
struct atmel_dma_buffer *pdc = &atmel_port->pdc_rx[i];
dma_unmap_single(port->dev,
pdc->dma_addr,
pdc->dma_size,
DMA_FROM_DEVICE);
kfree(pdc->buf);
}
}
if (atmel_use_dma_tx(port)) {
struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
dma_unmap_single(port->dev,
pdc->dma_addr,
pdc->dma_size,
DMA_TO_DEVICE);
}
/*
* Disable all interrupts, port and break condition.
*/
UART_PUT_CR(port, ATMEL_US_RSTSTA);
UART_PUT_IDR(port, -1);
/*
* Free the interrupt
*/
free_irq(port->irq, port);
/*
* If there is a specific "close" function (to unregister
* control line interrupts)
*/
if (atmel_close_hook)
atmel_close_hook(port);
}
/*
* Flush any TX data submitted for DMA. Called when the TX circular
* buffer is reset.
*/
static void atmel_flush_buffer(struct uart_port *port)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
if (atmel_use_dma_tx(port)) {
UART_PUT_TCR(port, 0);
atmel_port->pdc_tx.ofs = 0;
}
}
/*
* Power / Clock management.
*/
static void atmel_serial_pm(struct uart_port *port, unsigned int state,
unsigned int oldstate)
{
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
switch (state) {
case 0:
/*
* Enable the peripheral clock for this serial port.
* This is called on uart_open() or a resume event.
*/
clk_enable(atmel_port->clk);
/* re-enable interrupts if we disabled some on suspend */
UART_PUT_IER(port, atmel_port->backup_imr);
break;
case 3:
/* Back up the interrupt mask and disable all interrupts */
atmel_port->backup_imr = UART_GET_IMR(port);
UART_PUT_IDR(port, -1);
/*
* Disable the peripheral clock for this serial port.
* This is called on uart_close() or a suspend event.
*/
clk_disable(atmel_port->clk);
break;
default:
printk(KERN_ERR "atmel_serial: unknown pm %d/n", state);
}
}
/*
* Change the port parameters
*/
static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
struct ktermios *old)
{
unsigned long flags;
unsigned int mode, imr, quot, baud;
/* Get current mode register */
mode = UART_GET_MR(port) & ~(ATMEL_US_USCLKS | ATMEL_US_CHRL
| ATMEL_US_NBSTOP | ATMEL_US_PAR);
baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16);
quot = uart_get_divisor(port, baud);
if (quot > 65535) { /* BRGR is 16-bit, so switch to slower clock */
quot /= 8;
mode |= ATMEL_US_USCLKS_MCK_DIV8;
}
/* byte size */
switch (termios->c_cflag & CSIZE) {
case CS5:
mode |= ATMEL_US_CHRL_5;
break;
case CS6:
mode |= ATMEL_US_CHRL_6;
break;
case CS7:
mode |= ATMEL_US_CHRL_7;
break;
default:
mode |= ATMEL_US_CHRL_8;
break;
}
/* stop bits */
if (termios->c_cflag & CSTOPB)
mode |= ATMEL_US_NBSTOP_2;
/* parity */
if (termios->c_cflag & PARENB) {
/* Mark or Space parity */
if (termios->c_cflag & CMSPAR) {
if (termios->c_cflag & PARODD)
mode |= ATMEL_US_PAR_MARK;
else
mode |= ATMEL_US_PAR_SPACE;
} else if (termios->c_cflag & PARODD)
mode |= ATMEL_US_PAR_ODD;
else
mode |= ATMEL_US_PAR_EVEN;
} else
mode |= ATMEL_US_PAR_NONE;
spin_lock_irqsave(&port->lock, flags);
port->read_status_mask = ATMEL_US_OVRE;
if (termios->c_iflag & INPCK)
port->read_status_mask |= (ATMEL_US_FRAME | ATMEL_US_PARE);
if (termios->c_iflag & (BRKINT | PARMRK))
port->read_status_mask |= ATMEL_US_RXBRK;
if (atmel_use_dma_rx(port))
/* need to enable error interrupts */
UART_PUT_IER(port, port->read_status_mask);
/*
* Characters to ignore
*/
port->ignore_status_mask = 0;
if (termios->c_iflag & IGNPAR)
port->ignore_status_mask |= (ATMEL_US_FRAME | ATMEL_US_PARE);
if (termios->c_iflag & IGNBRK) {
port->ignore_status_mask |= ATMEL_US_RXBRK;
/*
* If we're ignoring parity and break indicators,
* ignore overruns too (for real raw support).
*/
if (termios->c_iflag & IGNPAR)
port->ignore_status_mask |= ATMEL_US_OVRE;
}
/* TODO: Ignore all characters if CREAD is set.*/
/* update the per-port timeout */
uart_update_timeout(port, termios->c_cflag, baud);
/* save/disable interrupts and drain transmitter */
imr = UART_GET_IMR(port);
UART_PUT_IDR(port, -1);
while (!(UART_GET_CSR(port) & ATMEL_US_TXEMPTY))
cpu_relax();
/* disable receiver and transmitter */
UART_PUT_CR(port, ATMEL_US_TXDIS | ATMEL_US_RXDIS);
/* set the parity, stop bits and data size */
UART_PUT_MR(port, mode);
/* set the baud rate */
UART_PUT_BRGR(port, quot);
UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);
/* restore interrupts */
UART_PUT_IER(port, imr);
/* CTS flow-control and modem-status interrupts */
if (UART_ENABLE_MS(port, termios->c_cflag))
port->ops->enable_ms(port);
spin_unlock_irqrestore(&port->lock, flags);
}
/*
* Return string describing the specified port
*/
static const char *atmel_type(struct uart_port *port)
{
return (port->type == PORT_ATMEL) ? "ATMEL_SERIAL" : NULL;
}
/*
* Release the memory region(s) being used by 'port'.
*/
static void atmel_release_port(struct uart_port *port)
{
struct platform_device *pdev = to_platform_device(port->dev);
int size = pdev->resource[0].end - pdev->resource[0].start + 1;
release_mem_region(port->mapbase, size);
if (port->flags & UPF_IOREMAP) {
iounmap(port->membase);
port->membase = NULL;
}
}
/*
* Request the memory region(s) being used by 'port'.
*/
static int atmel_request_port(struct uart_port *port)
{
struct platform_device *pdev = to_platform_device(port->dev);
int size = pdev->resource[0].end - pdev->resource[0].start + 1;
if (!request_mem_region(port->mapbase, size, "atmel_serial"))
return -EBUSY;
if (port->flags & UPF_IOREMAP) {
port->membase = ioremap(port->mapbase, size);
if (port->membase == NULL) {
release_mem_region(port->mapbase, size);
return -ENOMEM;
}
}
return 0;
}
/*
* Configure/autoconfigure the port.
*/
static void atmel_config_port(struct uart_port *port, int flags)
{
if (flags & UART_CONFIG_TYPE) {
port->type = PORT_ATMEL;
atmel_request_port(port);
}
}
/*
* Verify the new serial_struct (for TIOCSSERIAL).
*/
static int atmel_verify_port(struct uart_port *port, struct serial_struct *ser)
{
int ret = 0;
if (ser->type != PORT_UNKNOWN && ser->type != PORT_ATMEL)
ret = -EINVAL;
if (port->irq != ser->irq)
ret = -EINVAL;
if (ser->io_type != SERIAL_IO_MEM)
ret = -EINVAL;
if (port->uartclk / 16 != ser->baud_base)
ret = -EINVAL;
if ((void *)port->mapbase != ser->iomem_base)
ret = -EINVAL;
if (port->iobase != ser->port)
ret = -EINVAL;
if (ser->hub6 != 0)
ret = -EINVAL;
return ret;
}
static struct uart_ops atmel_pops = {
.tx_empty = atmel_tx_empty,
.set_mctrl = atmel_set_mctrl,
.get_mctrl = atmel_get_mctrl,
.stop_tx = atmel_stop_tx,
.start_tx = atmel_start_tx,
.stop_rx = atmel_stop_rx,
.enable_ms = atmel_enable_ms,
.break_ctl = atmel_break_ctl,
.startup = atmel_startup,
.shutdown = atmel_shutdown,
.flush_buffer = atmel_flush_buffer,
.set_termios = atmel_set_termios,
.type = atmel_type,
.release_port = atmel_release_port,
.request_port = atmel_request_port,
.config_port = atmel_config_port,
.verify_port = atmel_verify_port,
.pm = atmel_serial_pm,
};
/*
* Configure the port from the platform device resource info.
*/
static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port,
struct platform_device *pdev)
{
struct uart_port *port = &atmel_port->uart;
struct atmel_uart_data *data = pdev->dev.platform_data; //访问方式管理
port->iotype = UPIO_MEM; //访问方式为内存方式
port->flags = UPF_BOOT_AUTOCONF; //配置方式设置
port->ops = &atmel_pops; //串口的具体操作，串口驱动的关键实现
port->fifosize = 1; //FIFO缓存的大小
port->line = pdev->id;
port->dev = &pdev->dev;
port->mapbase = pdev->resource[0].start; //物理内存
port->irq = pdev->resource[1].start; //中断号
tasklet_init(&atmel_port->tasklet, atmel_tasklet_func,
(unsigned long)port);
memset(&atmel_port->rx_ring, 0, sizeof(atmel_port->rx_ring));
if (data->regs)
/* Already mapped by setup code */
port->membase = data->regs;
else {
port->flags |= UPF_IOREMAP;
port->membase = NULL;
}
/* for console, the clock could already be configured */
if (!atmel_port->clk) {
atmel_port->clk = clk_get(&pdev->dev, "usart");
clk_enable(atmel_port->clk);
port->uartclk = clk_get_rate(atmel_port->clk);
}
atmel_port->use_dma_rx = data->use_dma_rx;
atmel_port->use_dma_tx = data->use_dma_tx;
if (atmel_use_dma_tx(port))
port->fifosize = PDC_BUFFER_SIZE;
}
/*
* Register board-specific modem-control line handlers.
*/
void __init atmel_register_uart_fns(struct atmel_port_fns *fns)
{
if (fns->enable_ms)
atmel_pops.enable_ms = fns->enable_ms;
if (fns->get_mctrl)
atmel_pops.get_mctrl = fns->get_mctrl;
if (fns->set_mctrl)
atmel_pops.set_mctrl = fns->set_mctrl;
atmel_open_hook = fns->open;
atmel_close_hook = fns->close;
atmel_pops.pm = fns->pm;
atmel_pops.set_wake = fns->set_wake;
}
#ifdef CONFIG_SERIAL_ATMEL_CONSOLE
static void atmel_console_putchar(struct uart_port *port, int ch)
{
while (!(UART_GET_CSR(port) & ATMEL_US_TXRDY))
cpu_relax();
UART_PUT_CHAR(port, ch);
}
/*
* Interrupts are disabled on entering
*/
static void atmel_console_write(struct console *co, const char *s, u_int count)
{
struct uart_port *port = &atmel_ports[co->index].uart;
unsigned int status, imr;
unsigned int pdc_tx;
/*
* First, save IMR and then disable interrupts
*/
imr = UART_GET_IMR(port);
UART_PUT_IDR(port, ATMEL_US_RXRDY | ATMEL_US_TXRDY);
/* Store PDC transmit status and disable it */
pdc_tx = UART_GET_PTSR(port) & ATMEL_PDC_TXTEN;
UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);
uart_console_write(port, s, count, atmel_console_putchar);
/*
* Finally, wait for transmitter to become empty
* and restore IMR
*/
do {
status = UART_GET_CSR(port);
} while (!(status & ATMEL_US_TXRDY));
/* Restore PDC transmit status */
if (pdc_tx)
UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
/* set interrupts back the way they were */
UART_PUT_IER(port, imr);
}
/*
* If the port was already initialised (eg, by a boot loader),
* try to determine the current setup.
*/
static void __init atmel_console_get_options(struct uart_port *port, int *baud,
int *parity, int *bits)
{
unsigned int mr, quot;
/*
* If the baud rate generator isn't running, the port wasn't
* initialized by the boot loader.
*/
quot = UART_GET_BRGR(port) & ATMEL_US_CD;
if (!quot)
return;
mr = UART_GET_MR(port) & ATMEL_US_CHRL;
if (mr == ATMEL_US_CHRL_8)
*bits = 8;
else
*bits = 7;
mr = UART_GET_MR(port) & ATMEL_US_PAR;
if (mr == ATMEL_US_PAR_EVEN)
*parity = 'e';
else if (mr == ATMEL_US_PAR_ODD)
*parity = 'o';
/*
* The serial core only rounds down when matching this to a
* supported baud rate. Make sure we don't end up slightly
* lower than one of those, as it would make us fall through
* to a much lower baud rate than we really want.
*/
*baud = port->uartclk / (16 * (quot - 1));
}
static int __init atmel_console_setup(struct console *co, char *options)
{
struct uart_port *port = &atmel_ports[co->index].uart;
int baud = 115200;
int bits = 8;
int parity = 'n';
int flow = 'n';
if (port->membase == NULL) {
/* Port not initialized yet - delay setup */
return -ENODEV;
}
UART_PUT_IDR(port, -1);
UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);
if (options)
uart_parse_options(options, &baud, &parity, &bits, &flow);
else
atmel_console_get_options(port, &baud, &parity, &bits);
return uart_set_options(port, co, baud, parity, bits, flow);
}
static struct uart_driver atmel_uart;
static struct console atmel_console = {
.name = ATMEL_DEVICENAME,
.write = atmel_console_write,
.device = uart_console_device,
.setup = atmel_console_setup,
.flags = CON_PRINTBUFFER,
.index = -1,
.data = &atmel_uart,
};
#define ATMEL_CONSOLE_DEVICE &atmel_console
/*
* Early console initialization (before VM subsystem initialized).
*/
static int __init atmel_console_init(void)
{
if (atmel_default_console_device) {
add_preferred_console(ATMEL_DEVICENAME,
atmel_default_console_device->id, NULL);
atmel_init_port(&atmel_ports[atmel_default_console_device->id],
atmel_default_console_device);
register_console(&atmel_console);
}
return 0;
}
console_initcall(atmel_console_init);
/*
* Late console initialization.
*/
static int __init atmel_late_console_init(void)
{
if (atmel_default_console_device
&& !(atmel_console.flags & CON_ENABLED))
register_console(&atmel_console);
return 0;
}
core_initcall(atmel_late_console_init);
static inline bool atmel_is_console_port(struct uart_port *port)
{
return port->cons && port->cons->index == port->line;
}
#else
#define ATMEL_CONSOLE_DEVICE NULL
static inline bool atmel_is_console_port(struct uart_port *port)
{
return false;
}
#endif
static struct uart_driver atmel_uart = {
.owner = THIS_MODULE,
.driver_name = "atmel_serial",
.dev_name = ATMEL_DEVICENAME,
.major = SERIAL_ATMEL_MAJOR,
.minor = MINOR_START,
.nr = ATMEL_MAX_UART,
.cons = ATMEL_CONSOLE_DEVICE,
};
#ifdef CONFIG_PM
static bool atmel_serial_clk_will_stop(void)
{
#ifdef CONFIG_ARCH_AT91
return at91_suspend_entering_slow_clock();
#else
return false;
#endif
}
static int atmel_serial_suspend(struct platform_device *pdev,
pm_message_t state)
{
struct uart_port *port = platform_get_drvdata(pdev);
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
if (atmel_is_console_port(port) && console_suspend_enabled) {
/* Drain the TX shifter */
while (!(UART_GET_CSR(port) & ATMEL_US_TXEMPTY))
cpu_relax();
}
/* we can not wake up if we're running on slow clock */
atmel_port->may_wakeup = device_may_wakeup(&pdev->dev);
if (atmel_serial_clk_will_stop())
device_set_wakeup_enable(&pdev->dev, 0);
uart_suspend_port(&atmel_uart, port);
return 0;
}
static int atmel_serial_resume(struct platform_device *pdev)
{
struct uart_port *port = platform_get_drvdata(pdev);
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
uart_resume_port(&atmel_uart, port);
device_set_wakeup_enable(&pdev->dev, atmel_port->may_wakeup);
return 0;
}
#else
#define atmel_serial_suspend NULL
#define atmel_serial_resume NULL
#endif
//根据平台设备的资源构建一个atmle_uart_port结构，并将相关联的uart_port结构和uart_driver关联
static int __devinit atmel_serial_probe(struct platform_device *pdev)
{
struct atmel_uart_port *port;
void *data;
int ret;
BUILD_BUG_ON(!is_power_of_2(ATMEL_SERIAL_RINGSIZE));
port = &atmel_ports[pdev->id]; //串口都保存在atmel_ports数组中，平台设备的id即为数组索引
port->backup_imr = 0;
atmel_init_port(port, pdev); //构建uart_port结构
if (!atmel_use_dma_rx(&port->uart)) {
ret = -ENOMEM;
data = kmalloc(sizeof(struct atmel_uart_char) //使用DMA时DMA缓存分配
* ATMEL_SERIAL_RINGSIZE, GFP_KERNEL);
if (!data)
goto err_alloc_ring;
port->rx_ring.buf = data;
}
ret = uart_add_one_port(&atmel_uart, &port->uart); //把分配的端口加到uart_driver中
if (ret)
goto err_add_port;
device_init_wakeup(&pdev->dev, 1);
platform_set_drvdata(pdev, port);
return 0;
err_add_port:
kfree(port->rx_ring.buf);
port->rx_ring.buf = NULL;
err_alloc_ring:
if (!atmel_is_console_port(&port->uart)) {
clk_disable(port->clk);
clk_put(port->clk);
port->clk = NULL;
}
return ret;
}
11:35:00static struct platform_driver atmel_serial_driver = {
.probe = atmel_serial_probe,
.remove = __devexit_p(atmel_serial_remove),
.suspend = atmel_serial_suspend,
.resume = atmel_serial_resume,
.driver = {
.name = "atmel_usart",
.owner = THIS_MODULE,
},
};
static int __init atmel_serial_init(void)
{
int ret;
ret = uart_register_driver(&atmel_uart); //注册串口驱动
if (ret)
return ret;
ret = platform_driver_register(&atmel_serial_driver); //注册平台驱动
if (ret)
uart_unregister_driver(&atmel_uart);
return ret;
}
static void __exit atmel_serial_exit(void)
{
platform_driver_unregister(&atmel_serial_driver);
uart_unregister_driver(&atmel_uart);
}
module_init(atmel_serial_init);
module_exit(atmel_serial_exit);
MODULE_AUTHOR("Rick Bronson");
MODULE_DESCRIPTION("Atmel AT91 / AT32 serial port driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:atmel_usart");
我们顺着驱动加载流程对上面代码做简要分析：
1）当加载驱动时，代码首先执行atmel_serial_init函数，该函数向内核注册了两个驱动分别是struct uart_driver atmel_uart（我们的串口驱动）和struct platform_driver atmel_serial_driver(平台设备驱动，主要用于串口设备的探测和移除工作)，注意两个驱动的名称分别是atmel_serial和atmel_usart。
2）当平台驱动加载后会执行平台驱动的probe函数即atmel_serial_probe.在我们的驱动平台设备的加入是在arch/arm/mach-at91/at91sam9260_devices.c中加入的。具体相关代码如下：
/* --------------------------------------------------------------------
* UART
* -------------------------------------------------------------------- */
#if defined(CONFIG_SERIAL_ATMEL)
static struct resource dbgu_resources[] = {
[0] = {
.start = AT91_VA_BASE_SYS + AT91_DBGU,
.end = AT91_VA_BASE_SYS + AT91_DBGU + SZ_512 - 1,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = AT91_ID_SYS,
.end = AT91_ID_SYS,
.flags = IORESOURCE_IRQ,
},
};
static struct atmel_uart_data dbgu_data = {
.use_dma_tx = 0,
.use_dma_rx = 0, /* DBGU not capable of receive DMA */
.regs = (void __iomem *)(AT91_VA_BASE_SYS + AT91_DBGU),
};
static u64 dbgu_dmamask = DMA_BIT_MASK(32);
static struct platform_device at91sam9260_dbgu_device = {
.name = "atmel_usart",
.id = 0,
.dev = {
.dma_mask = &dbgu_dmamask,
.coherent_dma_mask = DMA_BIT_MASK(32),
.platform_data = &dbgu_data,
},
.resource = dbgu_resources,
.num_resources = ARRAY_SIZE(dbgu_resources),
};
static inline void configure_dbgu_pins(void)
{
at91_set_A_periph(AT91_PIN_PB14, 0); /* DRXD */
at91_set_A_periph(AT91_PIN_PB15, 1); /* DTXD */
}
static struct resource uart0_resources[] = {
[0] = {
.start = AT91SAM9260_BASE_US0,
.end = AT91SAM9260_BASE_US0 + SZ_16K - 1,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = AT91SAM9260_ID_US0,
.end = AT91SAM9260_ID_US0,
.flags = IORESOURCE_IRQ,
},
};
static struct atmel_uart_data uart0_data = {
.use_dma_tx = 1,
.use_dma_rx = 1,
};
static u64 uart0_dmamask = DMA_BIT_MASK(32);
static struct platform_device at91sam9260_uart0_device = {
.name = "atmel_usart",
.id = 1,
.dev = {
.dma_mask = &uart0_dmamask,
.coherent_dma_mask = DMA_BIT_MASK(32),
.platform_data = &uart0_data,
},
.resource = uart0_resources,
.num_resources = ARRAY_SIZE(uart0_resources),
};
static inline void configure_usart0_pins(unsigned pins)
{
at91_set_A_periph(AT91_PIN_PB4, 1); /* TXD0 */
at91_set_A_periph(AT91_PIN_PB5, 0); /* RXD0 */
if (pins & ATMEL_UART_RTS)
at91_set_A_periph(AT91_PIN_PB26, 0); /* RTS0 */
if (pins & ATMEL_UART_CTS)
at91_set_A_periph(AT91_PIN_PB27, 0); /* CTS0 */
if (pins & ATMEL_UART_DTR)
at91_set_A_periph(AT91_PIN_PB24, 0); /* DTR0 */
if (pins & ATMEL_UART_DSR)
at91_set_A_periph(AT91_PIN_PB22, 0); /* DSR0 */
if (pins & ATMEL_UART_DCD)
at91_set_A_periph(AT91_PIN_PB23, 0); /* DCD0 */
if (pins & ATMEL_UART_RI)
at91_set_A_periph(AT91_PIN_PB25, 0); /* RI0 */
}
static struct resource uart1_resources[] = {
[0] = {
.start = AT91SAM9260_BASE_US1,
.end = AT91SAM9260_BASE_US1 + SZ_16K - 1,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = AT91SAM9260_ID_US1,
.end = AT91SAM9260_ID_US1,
.flags = IORESOURCE_IRQ,
},
};
static struct atmel_uart_data uart1_data = {
.use_dma_tx = 1,
.use_dma_rx = 1,
};
static u64 uart1_dmamask = DMA_BIT_MASK(32);
static struct platform_device at91sam9260_uart1_device = {
.name = "atmel_usart",
.id = 2,
.dev = {
.dma_mask = &uart1_dmamask,
.coherent_dma_mask = DMA_BIT_MASK(32),
.platform_data = &uart1_data,
},
.resource = uart1_resources,
.num_resources = ARRAY_SIZE(uart1_resources),
};
static inline void configure_usart1_pins(unsigned pins)
{
/*add by shadow*/
at91_set_A_periph(AT91_PIN_PB6, 1); /* TXD1 */
/*shadow end*/
at91_set_A_periph(AT91_PIN_PB7, 0); /* RXD1 */
if (pins & ATMEL_UART_RTS)
at91_set_A_periph(AT91_PIN_PB28, 0); /* RTS1 */
if (pins & ATMEL_UART_CTS)
at91_set_A_periph(AT91_PIN_PB29, 0); /* CTS1 */
}
static struct resource uart2_resources[] = {
[0] = {
.start = AT91SAM9260_BASE_US2,
.end = AT91SAM9260_BASE_US2 + SZ_16K - 1,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = AT91SAM9260_ID_US2,
.end = AT91SAM9260_ID_US2,
.flags = IORESOURCE_IRQ,
},
};
static struct atmel_uart_data uart2_data = {
.use_dma_tx = 1,
.use_dma_rx = 1,
};
static u64 uart2_dmamask = DMA_BIT_MASK(32);
static struct platform_device at91sam9260_uart2_device = {
.name = "atmel_usart",
.id = 3,
.dev = {
.dma_mask = &uart2_dmamask,
.coherent_dma_mask = DMA_BIT_MASK(32),
.platform_data = &uart2_data,
},
.resource = uart2_resources,
.num_resources = ARRAY_SIZE(uart2_resources),
};
static inline void configure_usart2_pins(unsigned pins)
{
at91_set_A_periph(AT91_PIN_PB8, 1); /* TXD2 */
at91_set_A_periph(AT91_PIN_PB9, 0); /* RXD2 */
if (pins & ATMEL_UART_RTS)
at91_set_A_periph(AT91_PIN_PA4, 0); /* RTS2 */
if (pins & ATMEL_UART_CTS)
at91_set_A_periph(AT91_PIN_PA5, 0); /* CTS2 */
}
static struct resource uart3_resources[] = {
[0] = {
.start = AT91SAM9260_BASE_US3,
.end = AT91SAM9260_BASE_US3 + SZ_16K - 1,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = AT91SAM9260_ID_US3,
.end = AT91SAM9260_ID_US3,
.flags = IORESOURCE_IRQ,
},
};
static struct atmel_uart_data uart3_data = {
.use_dma_tx = 1,
.use_dma_rx = 1,
};
static u64 uart3_dmamask = DMA_BIT_MASK(32);
static struct platform_device at91sam9260_uart3_device = {
.name = "atmel_usart",
.id = 4,
.dev = {
.dma_mask = &uart3_dmamask,
.coherent_dma_mask = DMA_BIT_MASK(32),
.platform_data = &uart3_data,
},
.resource = uart3_resources,
.num_resources = ARRAY_SIZE(uart3_resources),
};
static inline void configure_usart3_pins(unsigned pins)
{
at91_set_A_periph(AT91_PIN_PB10, 1); /* TXD3 */
at91_set_A_periph(AT91_PIN_PB11, 0); /* RXD3 */
if (pins & ATMEL_UART_RTS)
at91_set_B_periph(AT91_PIN_PC8, 0); /* RTS3 */
if (pins & ATMEL_UART_CTS)
at91_set_B_periph(AT91_PIN_PC10, 0); /* CTS3 */
}
static struct resource uart4_resources[] = {
[0] = {
.start = AT91SAM9260_BASE_US4,
.end = AT91SAM9260_BASE_US4 + SZ_16K - 1,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = AT91SAM9260_ID_US4,
.end = AT91SAM9260_ID_US4,
.flags = IORESOURCE_IRQ,
},
};
static struct atmel_uart_data uart4_data = {
.use_dma_tx = 1,
.use_dma_rx = 1,
};
static u64 uart4_dmamask = DMA_BIT_MASK(32);
static struct platform_device at91sam9260_uart4_device = {
.name = "atmel_usart",
.id = 5,
.dev = {
.dma_mask = &uart4_dmamask,
.coherent_dma_mask = DMA_BIT_MASK(32),
.platform_data = &uart4_data,
},
.resource = uart4_resources,
.num_resources = ARRAY_SIZE(uart4_resources),
};
static inline void configure_usart4_pins(void)
{
at91_set_B_periph(AT91_PIN_PA31, 1); /* TXD4 */
at91_set_B_periph(AT91_PIN_PA30, 0); /* RXD4 */
}
static struct resource uart5_resources[] = {
[0] = {
.start = AT91SAM9260_BASE_US5,
.end = AT91SAM9260_BASE_US5 + SZ_16K - 1,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = AT91SAM9260_ID_US5,
.end = AT91SAM9260_ID_US5,
.flags = IORESOURCE_IRQ,
},
};
static struct atmel_uart_data uart5_data = {
.use_dma_tx = 1,
.use_dma_rx = 1,
};
static u64 uart5_dmamask = DMA_BIT_MASK(32);
static struct platform_device at91sam9260_uart5_device = {
.name = "atmel_usart",
.id = 6,
.dev = {
.dma_mask = &uart5_dmamask,
.coherent_dma_mask = DMA_BIT_MASK(32),
.platform_data = &uart5_data,
},
.resource = uart5_resources,
.num_resources = ARRAY_SIZE(uart5_resources),
};
static inline void configure_usart5_pins(void)
{
at91_set_A_periph(AT91_PIN_PB12, 1); /* TXD5 */
at91_set_A_periph(AT91_PIN_PB13, 0); /* RXD5 */
}
static struct platform_device *__initdata at91_uarts[ATMEL_MAX_UART]; /* the UARTs to use */
struct platform_device *atmel_default_console_device; /* the serial console device */
void __init at91_register_uart(unsigned id, unsigned portnr, unsigned pins)
{
struct platform_device *pdev;
switch (id) {
case 0: /* DBGU */
pdev = &at91sam9260_dbgu_device;
configure_dbgu_pins();
at91_clock_associate("mck", &pdev->dev, "usart");
break;
case AT91SAM9260_ID_US0:
pdev = &at91sam9260_uart0_device;
configure_usart0_pins(pins);
at91_clock_associate("usart0_clk", &pdev->dev, "usart");
break;
case AT91SAM9260_ID_US1:
pdev = &at91sam9260_uart1_device;
configure_usart1_pins(pins);
at91_clock_associate("usart1_clk", &pdev->dev, "usart");
break;
case AT91SAM9260_ID_US2:
pdev = &at91sam9260_uart2_device;
configure_usart2_pins(pins);
at91_clock_associate("usart2_clk", &pdev->dev, "usart");
break;
case AT91SAM9260_ID_US3:
pdev = &at91sam9260_uart3_device;
configure_usart3_pins(pins);
at91_clock_associate("usart3_clk", &pdev->dev, "usart");
break;
case AT91SAM9260_ID_US4:
pdev = &at91sam9260_uart4_device;
configure_usart4_pins();
at91_clock_associate("usart4_clk", &pdev->dev, "usart");
break;
case AT91SAM9260_ID_US5:
pdev = &at91sam9260_uart5_device;
configure_usart5_pins();
at91_clock_associate("usart5_clk", &pdev->dev, "usart");
break;
default:
return;
}
pdev->id = portnr; /* update to mapped ID */
if (portnr < ATMEL_MAX_UART)
at91_uarts[portnr] = pdev;
}
void __init at91_set_serial_console(unsigned portnr)
{
if (portnr < ATMEL_MAX_UART)
atmel_default_console_device = at91_uarts[portnr];
}
void __init at91_add_device_serial(void)
{
int i;
for (i = 0; i < ATMEL_MAX_UART; i++) {
if (at91_uarts[i])
platform_device_register(at91_uarts[i]);
}
if (!atmel_default_console_device)
printk(KERN_INFO "AT91: No default serial console defined./n");
}
#else
void __init at91_register_uart(unsigned id, unsigned portnr, unsigned pins) {}
void __init at91_set_serial_console(unsigned portnr) {}
void __init at91_add_device_serial(void) {}
#endif
在atmel_serial_probe函数中传入的参数就是上面加入的平台设备，注意这里的平台设备和平台驱动具有相同的名字。而前面加载的两个驱动的关联也在这个探测函数中得以体现，具体见上面的代码注解。其他比较好理解就是对uart_ops的实现