[U-Boot] [PATCH v4 1/3] dm: implement a MTD uclass

[Thomas Chou]

HI Jagan,

On 2015年11月07日 20:35, Jagan Teki wrote:
>> It seems we are working toward the same direction. :)
>
> Sorry, I couldn't understand this looks we're in different direction.
>
> Let me explain what I thought about mtd_info usage. udevice should be
> part of underlying flash structure's like cfi, nand and spi_flash and
> mtd_info should be used for it's core api's like _erase. _read and
> _write and underlying driver will use their global structure that
> include's mtd and udevice as a function pointer like this.

Please see v5 of this patch and v3 of altera qspi.

The uclass priv of mtd class is an auto-allocated mtd_info. The 
spi_flash_priv includes both mtd_info and spi_flash. So the only 
difference is the spi_flash. This is because cfi uses struct flash, 
while spi flash uses struct spi_flash. So it is better to leave the 
struct flash to driver allocation.

The mtd->priv points to struct spi_flash for spi flash, and points to 
struct flash for cfi flash. It serves the same purpose.

The struct flash has *mtd. The struct spi_flash has *mtd, too.

I added struct udevice *dev to mtd_info. The struct spi_flash has *dev, 
but struct flash has not.

>
> struct spi_flash {
>     struct mtd_info *info;
>     struct udevice *device;
> }
>

struct flash {
...
struct mtd_info *info;
}

> struct spi_flash_priv {
>          struct spi_flash        flash;
>          struct mtd_info         mtd;
> };
>

Simply,
struct mtd_info.


> static int spi_flash_std_probe(struct udevice *dev)
> {
>          struct spi_flash_priv *priv = dev_get_uclass_priv(dev);
>          struct spi_slave *spi = dev_get_parent_priv(dev);
>          struct spi_flash *flash;
>          int ret;
>
>          flash = &priv->flash;
>          flash->mtd = &priv->mtd;

mtd = dev_get_uclass_priv(dev);
flash->mtd = mtd;

>
>          flash->spi = spi;
>          flash->priv = priv;
>
>          priv->mtd.priv = flash;
>          flash->dev = dev;

mtd->priv = flash;
mtd->dev = dev;

flash->mtd->dev is the same as spi's flash->dev

> }
>
> U_BOOT_DRIVER(spi_flash_std) = {
>          .name           = "spi_flash_std",
>          .id             = UCLASS_SPI_FLASH,
>          .of_match       = spi_flash_std_ids,
>          .probe          = spi_flash_std_probe,
>          .priv_auto_alloc_size = sizeof(struct spi_flash_priv),
> };
>
> This is the way I have implemented mtd on spi-flash[1] [2]
> [1] https://patchwork.ozlabs.org/patch/529397/
> [2] https://patchwork.ozlabs.org/patch/529399/
>
> Please explain how this related your approach of adding udevice to mtd.
>

The flash ops which u-boot commands calls are built upon mtd ops.

eg,
write_buff()
{
   mtd_write();
}

flash_erase()
{
   mtd_erase();
}

Please let me know what do you think. Thanks. :)

Best regards,
Thomas