arm linux debug notes (error note)
1. forgot __func__ and pointer is judged too earlily.
ret = sprdfb_panel_constructor(pan_node, fb_dev);
if (ret) {
pr_err("%s: failed to construct panel device\n"); // lose __func__
return -EFAULT;
}%s, __func__, forgot __func__
if (!fb_dev || fb_dev->panel)
return -ENODEV; // Actually, panel pointer is NULL...
pan_node = sprdfb_panel_search(fb_dev);
if (!pan_node) {
pr_warn("can't find panel specified by cmdline, try reading id\n");
}
ret = sprdfb_panel_constructor(pan_node, fb_dev);
if (ret) {
pr_err("%s: failed to construct panel device\n", __func__);
return -EFAULT;
}
panel = fb_dev->panel;The error log is as following:
7sprdfb_panel: ---- enter: sprdfb_panel_device_register ----
1Unable to handle kernel paging request at virtual address 60000113
1pgd = c0004000
1[60000113] *pgd=00000000
0Internal error: Oops: 5 [#1] PREEMPT SMP ARM
dModules linked in:
dCPU: 1 PID: 1 Comm: swapper/0 Tainted: G W 3.10.17-00026-g6d61c92-dirty #29
dtask: d7098000 ti: d70a0000 task.ti: d70a0000
PC is at strnlen+0x1c/0x30
LR is at string.isra.3+0x34/0xc8
pc : [] lr : [] psr: 20000193 // stopped at printk, actually is pr_err.
sp : d70a1c78 ip : 00000020 fp : d70a1d58
r10: c055827b r9 : c084b0e0 r8 : 00000000
r7 : 60000113 r6 : ffffffff r5 : c084b0e0 r4 : c084ad0a
r3 : 60000113 r2 : 60000113 r1 : 60000112 r0 : 60000113 // 6000113 is a abnormal address!!!
Flags: nzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment kernel
Control: 10c53c7d Table: 8000406a DAC: 00000015
2. pointer should not NULL
porch = kzalloc(sizeof(struct timing_rgb), GFP_KERNEL);
panel = kzalloc(sizeof(struct panel_spec), GFP_KERNEL);
if (!panel || porch) // judge porch not right, should !porch
goto alloc_panel_mem_error;
3. The field name doesn't not match
name = (char *)of_get_property(pan_node,
"sprdfb,dispc-dsi-panel-name", NULL);
if (!name) {
strlcpy(panel->panel_name, "unspecified", PANEL_NAME_LEN);
ret = -ENXIO;
pr_err("%s:%d, Panel name not specified\n",
__func__, __LINE__);
goto parse_dt_error;
} else {
strlcpy(panel->panel_name, name, PANEL_NAME_LEN);
pr_info("%s: Panel: %s is specified\n",
__func__, panel->panel_name);
}The name in dtsi is "dispc-panel-name", but in source code, the name is "dispc-dsi-panel-name".
4. NULL Pointer
static int sprdfb_panel_parse_dcs_cmds(const struct device_node *np,
struct dsi_cmds_list *pcmds, char *cmd_key)
{
const char *data;
int dt_len = 0, len;
char *buf, *bp;
struct dsi_cmd_desc *d;
int cnt = 0;
pr_debug("---- enter: %s ----\n", __func__);
data = of_get_property(np, cmd_key, &dt_len);
if (!data) {
pr_err("%s: failed, key=%s\n", __func__, cmd_key);
return -ENOMEM;
}
buf = kzalloc(sizeof(char) * dt_len, GFP_KERNEL);
if (!buf)
return -ENOMEM;
memcpy(buf, data, dt_len);
/* scan dcs commands */
bp = buf;
len = dt_len;
d = (struct dsi_cmd_desc *)bp;
d->c_len = ntohs(d->c_len); // If d is NULL, now dereference it, kernel will be dumped.
while (len > (sizeof(*d) + d->c_len)) {
if (d->c_len > len) {
pr_err("%s: dtsi cmd=%x error, len=%d",
__func__, d->data_type, d->c_len);
goto exit_free;
}
pr_debug("data type is %d, cmd len is %d\n",
d->data_type, d->c_len);
bp += sizeof(*d) + d->c_len;
len -= sizeof(*d) + d->c_len;
d = (struct dsi_cmd_desc *)bp;
d->c_len = ntohs(d->c_len);
cnt++;
}
pcmds->cmds_cnt = cnt;
pcmds->cmds = (struct dsi_cmd_desc *)buf;
return 0;
exit_free:
kfree(buf);
return -EFAULT;
}5. Init sequence for using dts
1) platform_bus_init
2) iomap
3) register all platform_driver to platform_driver bus
4) hwspinlock init
4.1 find the hwspinlock node in DTS
4.2 register the hwspinlock device to platform_device bus
4.3 hwspinlock probe() and init the hwspinlock data struct
4.4 early_init_hwspinlock
5) ADI_init and ADC_init
6) populate the DT, register all devices to platform_device bus
6. name is defined wrongly
data = (char *)of_get_property(node,
"sprdfb,dispc-dsi-color-mode-polarity", NULL);
if (data) {
if (!strcmp(data, "negative"))
panel->info.mipi->color_mode_pol = SPRDFB_POLARITY_NEG;
else
panel->info.mipi->color_mode_pol = SPRDFB_POLARITY_POS;
} else
panel->info.mipi->color_mode_pol = SPRDFB_POLARITY_POS;The field "sprdfb,dispc-dsi-color-mode-polarity" is right, but previously, it is wrong, "-polarity" is missed.
In dtsi, the field is as following:
sprdfb,dispc-dsi-h-sync-polarity = "positive";
sprdfb,dispc-dsi-v-sync-polarity = "positive";
sprdfb,dispc-dsi-de-polarity = "positive";
sprdfb,dispc-dsi-te-polarity = "positive";
sprdfb,dispc-dsi-color-mode-polarity = "negative";
sprdfb,dispc-dsi-shut-down-polarity = "negative";7. pointer to pointers and dsi commands
static int sprdfb_dsi_tx_cmds(struct panel_spec *panel,
struct dsi_cmd_desc **cmds, u32 cmds_len, bool force_lp)
{
int i, time, len;
struct ops_mipi *ops = panel->info.mipi->ops;
u8 *data;
u16 work_mode = panel->info.mipi->work_mode;
pr_info("%s, len: %d\n", __func__, cmds_len);
if (!ops->mipi_set_cmd_mode ||
!ops->mipi_dcs_write ||
!ops->mipi_set_hs_mode ||
!ops->mipi_set_lp_mode ||
!ops->mipi_force_write) {
pr_err("%s: Expected functions are NULL.\n", __func__);
return -EFAULT;
}
if (force_lp) {
if (work_mode == SPRDFB_MIPI_MODE_CMD)
ops->mipi_set_lp_mode();
else
ops->mipi_set_data_lp_mode();
}
ops->mipi_set_cmd_mode();
for (i = 0; i < cmds_len; i++) {
if (cmds[i]->data_type != DCS_SHORT_WRITE_0 &&
cmds[i]->data_type != DCS_SHORT_WRITE_1) {
len = cmds[i]->c_len + sizeof(cmds[i]->c_len);
data = cmds[i]->payload - sizeof(cmds[i]->c_len);
} else {
len = cmds[i]->c_len;
data = cmds[i]->payload;
}
pr_debug("dsi write cmd type: %d, len: %d\n",
cmds[i]->data_type, len);
if (cmds[i]->data_type == GENERIC_LONG_WRITE)
ops->mipi_force_write(GENERIC_LONG_WRITE, data, len);
else
ops->mipi_dcs_write(data, len);
if (cmds[i]->wait_time) {
time = cmds[i]->wait_time * 1000;
usleep_range(time, time);
}
}
if (force_lp) {
if (work_mode == SPRDFB_MIPI_MODE_CMD)
ops->mipi_set_hs_mode();
else
ops->mipi_set_data_hs_mode();
}
return 0;
}struct dsi_cmds_list {
struct dsi_cmd_desc *cmds[PANEL_MAX_CMDS_LEN];
u32 cmds_cnt;
};struct dsi_cmd_desc {
u8 data_type; /* BYTE[0] */
u8 reserved; /* BYTE[1]: reserved */
u8 wait_time; /* BYTE[2] */
u16 c_len; /* BYTE[3...4]: cmd lenght */
u8 payload[0]; /* BYTE[5] */
} __packed;/* 05: DCS short Wr; 39: DCS long Wr; 06: DCS read; 15: DCS short Wr */
#define GENERIC_SHORT_WRITE_0 0x03
#define GENERIC_SHORT_WRITE_1 0x13
#define GENERIC_SHORT_WRITE_2 0x23
#define GENERIC_LONG_WRITE 0x29
#define DCS_SHORT_WRITE_0 0x05
#define DCS_SHORT_WRITE_1 0x15
#define DCS_LONG_WRITE 0x39
#define GENERIC_SHORT_READ_0 0x04
#define GENERIC_SHORT_READ_1 0x14
#define GENERIC_SHORT_READ_2 0x24
#define DCS_READ_0 0x06
#define SET_MAX_RET_PKT_SIZE 0x37Parsing and handling commands of dsi are not easy. They should be paid a lot of attention to.
static int sprdfb_panel_parse_dcs_cmds(const struct device_node *np,
struct dsi_cmds_list *pcmds, char *cmd_key)
{
const char *data;
int dt_len = 0, len, header;
char *buf, *bp;
int cnt = 0;
pr_debug("---- enter: %s ----\n", __func__);
data = of_get_property(np, cmd_key, &dt_len);
if (!data) {
pr_err("%s: failed, key=%s\n", __func__, cmd_key);
return -ENOMEM;
}
buf = kzalloc(sizeof(char) * dt_len, GFP_KERNEL);
if (!buf)
return -ENOMEM;
memcpy(buf, data, dt_len);
/* scan dcs commands */
bp = buf;
len = dt_len;
header = sizeof(struct dsi_cmd_desc);
while (len > header) {
pcmds->cmds[cnt] = (struct dsi_cmd_desc *)bp;
pcmds->cmds[cnt]->c_len = ntohs(pcmds->cmds[cnt]->c_len);
if (pcmds->cmds[cnt]->c_len > len) {
pr_err("%s: data type is 0x%x error, len=%d\n",
__func__, pcmds->cmds[cnt]->data_type,
pcmds->cmds[cnt]->c_len);
goto exit_free;
}
pr_debug("data type is 0x%x, cmd len is %d, remaining(%d), "
"cnt(%d)\n", pcmds->cmds[cnt]->data_type,
pcmds->cmds[cnt]->c_len, len, cnt + 1);
bp += header;
len -= header;
bp += pcmds->cmds[cnt]->c_len;
len -= pcmds->cmds[cnt]->c_len;
cnt++;
}
pcmds->cmds_cnt = cnt;
return 0;
exit_free:
kfree(buf);
return -EFAULT;
}6. virtual address and physical address switch
trace32 -> CPU -> peripheral -> System Control and Config -> SCTLR_EL1 -> M -> enable (enable virtual address) / disable (physical address)
7 linux flags
__attribute__
__attribute__(section)，用来修饰函数时，可以使你把代码放在image的不同段，如:
void f(void) __attribute__((section(“new_section”)));
函数f()将被放到只读new_section段中，而不是.text中。
__attribute((regparm(0)))，表示不从寄存器中传递参数，如果是regparm(3)则调用函数的时候参数不是通过栈传递，而是直接放到寄存器里，被调用函数直接从寄存器取参数。gcc编译器在汇编过程中调用c语言函数时传递参数有两种方法：一种是通过堆栈，另一种是通过寄存器，缺省使用寄存器，假如想通过堆栈传递，定义的c函数时要在函数前加上宏asmlinkage
asmlinkage
在看内核源代码start_kernel函数时，第一个遇到的疑问是asmlinkage，原来asmlinkage是一个宏，它定义在文件include/asm-i386/linkage.h中，具体如下：
＃define
asmlinkage CPP_ASMLINKAGE
__attribute__((regparm(0)))，其中CPP_ASMLINKAGE也是一个宏，定义在include/linux/linkage.h头文件中，具体为：
#define CPP_ASMLINKAGE extern "C"，
extern “C”是用来实现C＋＋和C的混合编程，而
__attribute__是关键字，是gcc的C语言扩展，它可以设置函数属性（Function Attribute）、变量属性（Variable Attribute）和类型属性（Type Attribute），总的来说，asmlinkage是个宏，使用它是为了保持参数在stack中，因为从汇编语言到C语言代码参数的传递是通过stack的，它也可能从stack中得到一些不需要的参数，asmlinkage将要解析那些参数。
__init
是一个宏定义，定义在arch/um/include/init.h文件中，具体如：
#define __init __attribute__ ((__section__ (".init.text")))
这个标志符和函数声明放在一起，它表示gcc编译器在编译的时候需要把这个函数放在.init.text中，而这个section在内核完成初始化之后会被释放掉。
__weak
是一个宏定义，定义在include/asm-mips/linkage.h文件中，具体如：
#define __weak __attribute__((weak))，它常用于函数和变量的声明和函数的定义，
是GNU compiler的扩展，被ARM compiler支持，可以将一个函数声明为weak,
当没有其他同名函数声明时调用weak,有其他同名函数时调用其他同名函数。
__va(x)
是个宏，定义在include/asm-alpha/page.h文件中，具体如下：
#define __va(x) ((void *)((unsigned long)(x) + PAGE_OFFSET))
__pa(x)
也是个宏，定义在include/asm-alpha/page.h文件中，具体如下：
#define __pa(x) ((unsigned long)(x)-PAGE_OFFSET),
其中的PAGE_OFFSET定义为0xffff800000000000UL或0xfffffc0000000000UL
register
可以用来修饰变量，表示寄存器变量，只能用于整型和字符变量，表示变量被存储在CPU的寄存器中， 而不像普通变量被存储在内存中，这样可以提高运算速度，它常用于在同一变量名频繁出现的地方，且 它只适用于局部变量和函数的形式参数，它属于auto型变量，不能作为全局变量
EXPORT_SYMBOL
若内核函数或变量要被内核模块调用，则必须使用EXPORT_SYMBOL宏进行处理，作用之一是将该符 号连接到二进制文件的各个__ksymtab_xx_xx section，内核加载模块时，会先确认该模块调用的各内 核函数是否已export，也就是说EXPORT_SYMBOL可以将一个函数或变量以符号的方式导出给其他模块使用。