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

Thomas Chou
2015-11-07T13:43:28Z

HI Jagan,

On 2015?11?07? 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