Re: [PATCH v4 2/3] mtd: cfi_cmdset_0002: Use chip_ready() for write on S29GL064N

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Tokunori,

ikegami.t@gmail.com wrote on Thu, 17 Mar 2022 00:54:54 +0900:

> As pointed out by this bug report [1], buffered writes are now broken on
> S29GL064N. This issue comes from a rework which switched from using chip_good()
> to chip_ready(), because DQ true data 0xFF is read on S29GL064N and an error
> returned by chip_good().

Vignesh, I believe you understand this issue better than I do, can you
propose an improved commit log?

> One way to solve the issue is to revert the change
> partially to use chip_ready for S29GL064N.
> 
> [1] https://lore.kernel.org/r/b687c259-6413-26c9-d4c9-b3afa69ea124@pengutronix.de/
> 
> Fixes: dfeae1073583("mtd: cfi_cmdset_0002: Change write buffer to check correct value")
> Signed-off-by: Tokunori Ikegami <ikegami.t@gmail.com>
> Tested-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> Cc: stable@vger.kernel.org
> ---
>  drivers/mtd/chips/cfi_cmdset_0002.c | 25 +++++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c
> index e68ddf0f7fc0..6c57f85e1b8e 100644
> --- a/drivers/mtd/chips/cfi_cmdset_0002.c
> +++ b/drivers/mtd/chips/cfi_cmdset_0002.c
> @@ -866,6 +866,23 @@ static int __xipram chip_check(struct map_info *map, struct flchip *chip,
>  		chip_check(map, chip, addr, &datum); \
>  	})
>  
> +static bool __xipram cfi_use_chip_ready_for_write(struct map_info *map)

At the very least I would call this function:
cfi_use_chip_ready_for_writes()

Yet, I still don't fully get what chip_ready is versus chip_good.

> +{
> +	struct cfi_private *cfi = map->fldrv_priv;
> +
> +	return cfi->mfr == CFI_MFR_AMD && cfi->id == 0x0c01;
> +}
> +
> +static int __xipram chip_good_for_write(struct map_info *map,
> +					struct flchip *chip, unsigned long addr,
> +					map_word expected)
> +{
> +	if (cfi_use_chip_ready_for_write(map))
> +		return chip_ready(map, chip, addr);

If possible and not too invasive I would definitely add a "quirks" flag
somewhere instead of this cfi_use_chip_ready_for_write() check.

Anyway, I would move this to the chip_good() implementation directly so
we partially hide the quirks complexity from the core.

> +
> +	return chip_good(map, chip, addr, expected);
> +}
> +
>  static int get_chip(struct map_info *map, struct flchip *chip, unsigned long adr, int mode)
>  {
>  	DECLARE_WAITQUEUE(wait, current);
> @@ -1686,7 +1703,7 @@ static int __xipram do_write_oneword_once(struct map_info *map,
>  		 * "chip_good" to avoid the failure due to scheduling.
>  		 */
>  		if (time_after(jiffies, timeo) &&
> -		    !chip_good(map, chip, adr, datum)) {
> +		    !chip_good_for_write(map, chip, adr, datum)) {
>  			xip_enable(map, chip, adr);
>  			printk(KERN_WARNING "MTD %s(): software timeout\n", __func__);
>  			xip_disable(map, chip, adr);
> @@ -1694,7 +1711,7 @@ static int __xipram do_write_oneword_once(struct map_info *map,
>  			break;
>  		}
>  
> -		if (chip_good(map, chip, adr, datum)) {
> +		if (chip_good_for_write(map, chip, adr, datum)) {
>  			if (cfi_check_err_status(map, chip, adr))
>  				ret = -EIO;
>  			break;
> @@ -1966,14 +1983,14 @@ static int __xipram do_write_buffer_wait(struct map_info *map,
>  		 * "chip_good" to avoid the failure due to scheduling.
>  		 */
>  		if (time_after(jiffies, timeo) &&
> -		    !chip_good(map, chip, adr, datum)) {
> +		    !chip_good_for_write(map, chip, adr, datum)) {
>  			pr_err("MTD %s(): software timeout, address:0x%.8lx.\n",
>  			       __func__, adr);
>  			ret = -EIO;
>  			break;
>  		}
>  
> -		if (chip_good(map, chip, adr, datum)) {
> +		if (chip_good_for_write(map, chip, adr, datum)) {
>  			if (cfi_check_err_status(map, chip, adr))
>  				ret = -EIO;
>  			break;


Thanks,
Miquèl