1.spi控制器加载

由spi控制器驱动程序调用spi_register_master来完成spi控制器驱动加载

int spi_register_master(struct spi_master *master)
{
...

   status = of_spi_register_master(master); //片选gpio的解析，片选是在控制器配置的

...
   if (master->transfer)
       dev_info(dev, "master is unqueued, this is deprecated\n");
   else {
       status = spi_master_initialize_queue(master);　　　//消息队列的初始化
       if (status) {
           device_del(&master->dev);
           goto done;
       }
   }
   /* add statistics */
   spin_lock_init(&master->statistics.lock);

   mutex_lock(&board_lock);
   list_add_tail(&master->list, &spi_master_list);
   list_for_each_entry(bi, &board_list, list)
       spi_match_master_to_boardinfo(master, &bi->board_info)

//这里是通过spi_register_board_info调用，产生的spi device需要解析并添加到maste链表上
   mutex_unlock(&board_lock);

   /* Register devices from the device tree and ACPI */
   of_register_spi_devices(master);　　　//spi device的添加
   acpi_register_spi_devices(master);　　//acpi设备的添加，这里不关注
done:
   return status;
}

2.片选的解析

以上是spi master，基本上芯片提供商都有自己的解决方案一般不需要我们改动。与我们相关的是spi device dtsi的配置

3.spi device的添加

static void of_register_spi_devices(struct spi_master *master)
{
   struct spi_device *spi;
   struct device_node *nc;

   if (!master->dev.of_node)
       return;

   for_each_available_child_of_node(master->dev.of_node, nc) {
       if (of_node_test_and_set_flag(nc, OF_POPULATED))
           continue;
       spi = of_register_spi_device(master, nc);
       if (IS_ERR(spi))
           dev_warn(&master->dev, "Failed to create SPI device for %s\n",
               nc->full_name);
   }
}

of_register_spi_device(struct spi_master *master, struct device_node *nc)
{
   struct spi_device *spi;
   int rc;
   u32 value;

   /* Alloc an spi_device */
   spi = spi_alloc_device(master);
   if (!spi) {
       dev_err(&master->dev, "spi_device alloc error for %s\n",
           nc->full_name);
       rc = -ENOMEM;
       goto err_out;
   }

   /* Select device driver */从node中获取compatible属性，然后填充
   rc = of_modalias_node(nc, spi->modalias,
               sizeof(spi->modalias));
   if (rc < 0) {
       dev_err(&master->dev, "cannot find modalias for %s\n",
           nc->full_name);
       goto err_out;
   }

   /* Device address */
   rc = of_property_read_u32(nc, "reg", &value);
   if (rc) {
       dev_err(&master->dev, "%s has no valid 'reg' property (%d)\n",
           nc->full_name, rc);
       goto err_out;
   }
   spi->chip_select = value;

//这个reg是spi device必需配置项，且不能大于master设置的最大片选值。主要是设置片选的下标，因为片选数组是在master里面配置的

   /* Mode (clock phase/polarity/etc.) */
   if (of_find_property(nc, "spi-cpha", NULL))
       spi->mode |= SPI_CPHA;
   if (of_find_property(nc, "spi-cpol", NULL))
       spi->mode |= SPI_CPOL;
   if (of_find_property(nc, "spi-cs-high", NULL))
       spi->mode |= SPI_CS_HIGH;
   if (of_find_property(nc, "spi-3wire", NULL))
       spi->mode |= SPI_3WIRE;
   if (of_find_property(nc, "spi-lsb-first", NULL))
       spi->mode |= SPI_LSB_FIRST;

   /* Device DUAL/QUAD mode */
   if (!of_property_read_u32(nc, "spi-tx-bus-width", &value)) {
       switch (value) {
       case 1:
           break;
       case 2:
           spi->mode |= SPI_TX_DUAL;
           break;
       case 4:
           spi->mode |= SPI_TX_QUAD;
           break;
       default:
           dev_warn(&master->dev,
               "spi-tx-bus-width %d not supported\n",
               value);
           break;
       }
   }

   if (!of_property_read_u32(nc, "spi-rx-bus-width", &value)) {
       switch (value) {
       case 1:
           break;
       case 2:
           spi->mode |= SPI_RX_DUAL;
           break;
       case 4:
           spi->mode |= SPI_RX_QUAD;
           break;
       default:
           dev_warn(&master->dev,
               "spi-rx-bus-width %d not supported\n",
               value);
           break;
       }
   }

//上面是spi mode配置，可以在dtsi里面直接配置，也可以在spi_driver匹配成功后，调用spi_setup重新设定mode

   /* Device speed */
   rc = of_property_read_u32(nc, "spi-max-frequency", &value);
   if (rc) {
       dev_err(&master->dev, "%s has no valid 'spi-max-frequency' property (%d)\n",
           nc->full_name, rc);
       goto err_out;
   }
   spi->max_speed_hz = value;

//spi最大速率，必需配置

   /* Store a pointer to the node in the device structure */
   of_node_get(nc);
   spi->dev.of_node = nc;

//主要是作一些检测，没有问题完成device添加。这里注意的是如果同相的控制器上片选配置已经存在链表上，那么这个spi device将会添加失败
   rc = spi_add_device(spi);
   if (rc) {
       dev_err(&master->dev, "spi_device register error %s\n",
           nc->full_name);
       goto err_out;
   }

   return spi;

err_out:
   spi_dev_put(spi);
   return ERR_PTR(rc);
}

从上面大体可知，一个spi device dtsi有两个配置项必需存在

1.reg

2.spi-max-frequency

4.spi中断的解析

在驱动匹配成功后，probe加载时会解析中断。这里只需要按中断配置的方式来正常配置中断就好了. eg:

#interrupt-cells : Defines the width of cells used to represent interrupts. Typically this value is <2>,

which includes a 32-bit number that represents the interrupt number,

and a 32-bit number that represents the interrupt sense and level.

一般device我们用到的#interrupt-cells配置是２,表示有２个参数。一个是中断后，另一个是中断触发方式
#define IRQ_TYPE_NONE       0
#define IRQ_TYPE_EDGE_RISING   1
#define IRQ_TYPE_EDGE_FALLING   2
#define IRQ_TYPE_EDGE_BOTH   (IRQ_TYPE_EDGE_FALLING | IRQ_TYPE_EDGE_RISING)
#define IRQ_TYPE_LEVEL_HIGH   4
#define IRQ_TYPE_LEVEL_LOW   8

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