kernel 3.18,mcp2515 implemented in AT91SAM9G25

mcp2515的嵌入式linux的用例，网上的资料基本都是应用到比较老的内核。步骤基本无异。

本文的内容，是基于dts配置的设备支持；需要做的工作主要有两部分；dts的构建和代码的少量修改。

1.硬件连接：

外设------iso1050-----mcp2515----cpu

cpu与mcp2515之间采用spi通信方式，利用的cpu的spi0接口，片上的spi0。

2.dts的编写

1）、

      spi0: spi@f0000000 {
				#address-cells = <1>;
				#size-cells = <0>;
				compatible = "atmel,at91rm9200-spi";
				reg = <0xf0000000 0x100>;
				interrupts = <13 IRQ_TYPE_LEVEL_HIGH 3>;
				dmas = <&dma0 1 AT91_DMA_CFG_PER_ID(1)>,
				       <&dma0 1 AT91_DMA_CFG_PER_ID(2)>;
				dma-names = "tx", "rx";
				pinctrl-names = "default";
				pinctrl-0 = <&pinctrl_spi0>;
				clocks = <&spi0_clk>;
				clock-names = "spi_clk";
				cs-gpios = <&pioA 14 GPIO_ACTIVE_LOW>;
				status = "okay";
			};

spi这个大同小异，每个片子的配置差不多。注意的就是cs-gpios，片选的gpio。

2）、
mcp2515的dnode编写

clocks {

	mcp251x: mcp251x_xtal {
		compatible = "fixed-clock";
		#clock-cells = <0>;
		clock-frequency = <8000000>;//8Mhz，这个时钟的大小和原理图mcp2515外挂的晶振大小有关 8MHZ or 16MHZ
	};
};
ahb{
	 apb{

			spi0: spi@f0000000 {
					can0: can@0 {
						compatible = "microchip,mcp2515";
						reg = <0>;//cs 0
						clocks = <&mcp251x>;
						clock-names = "mcp251x_clk";
						spi-max-frequency = <25000000>;//25Mhz
						interrupt-parent = <&pioC>;//pc
						interrupts = <30 IRQ_TYPE_EDGE_FALLING>;//falling edge trigger 中断依据原理图的mcp2515的INT接到cpu的位置
						rst-gpios = <&pioC 5 0>;//依赖于mcp2515的reset接到cpu的哪个pin
						int-gpios = <&pioC 30 0>;<span style="font-family: Arial, Helvetica, sans-serif;">//依赖于mcp2515的INT接到cpu的哪个pin</span>
						//vdd-supply = <&reg_can>;
						//xceiver-supply = <&reg5v0>;
					};
			};
			
	};
};

dts的修改具体可参考 microchip,mcp251x.txt

3.代码修改

mcp251x.c

struct mcp251x_priv {
	....

    //mcp reset pin  and interrupt pin desc
    struct gpio_desc *rst_gpio;
    struct gpio_desc *int_gpio;
	....
}

static int mcp251x_can_probe(struct spi_device *spi)
{
	... ...
	
    priv->rst_gpio = devm_gpiod_get_index(&spi->dev,"rst",0x00);
    if (IS_ERR_OR_NULL(priv->rst_gpio))
    {
        priv->rst_gpio =  NULL;
        //printk("get rst gpio error!!\n");
    }
    else
    {
        err = gpiod_direction_output(priv->rst_gpio, 1);
        if (err) {
			dev_dbg(&spi->dev, "Unable to set input direction for mcp2515 INT GPIO");
		}
        //printk("set rst gpio output!!\n");
    }
    priv->int_gpio = devm_gpiod_get_index(&spi->dev,"int",0x00);
    if (IS_ERR_OR_NULL(priv->int_gpio))
    {
        priv->int_gpio =  NULL;
        //printk("get int gpio error!!\n");
    }
    else
    {
        err = gpiod_direction_input(priv->int_gpio);
        if (err) {
			dev_dbg(&spi->dev, "Unable to set input direction for mcp2515 INT GPIO");
		}
        //printk("set int gpio input!!\n");
    }

	... ...
};