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

[Tokunori Ikegami]

Hi Ahmad-san,

On 2022/03/17 23:16, Ahmad Fatoum wrote:
> Hello Vignesh,
>
> On 17.03.22 11:01, Vignesh Raghavendra wrote:
>>
>> On 16/03/22 10:51 pm, Miquel Raynal wrote:
>>> Hi Tokunori,
>>>
>>> ikegami.t at 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?
>> How about:
>>
>> Since commit dfeae1073583("mtd: cfi_cmdset_0002: Change write buffer to
>> check correct value") buffered writes fail on S29GL064N. This is
>> because, on S29GL064N, reads return 0xFF at the end of DQ polling for
>> write completion, where as, chip_good() check expects actual data
>> written to the last location to be returned post DQ polling completion.
>> Fix is to revert to using chip_good() for S29GL064N which only checks
>> for DQ lines to settle down to determine write completion.
> Message sounds good to me with one remark: The issue is independent of
> whether buffered writes are used or not. It's just because buffered writes
> are the default, that it was broken by dfeae1073583 ("mtd: cfi_cmdset_0002:
> Change write buffer to check correct value"). The word write case was broken
> by 37c673ade35c ("mtd: cfi_cmdset_0002: Use chip_good() to retry in
> do_write_oneword()"), so the commit message should probably reference
> both. as this commit indeed fixes both FORCE_WORD_WRITE == 0 and == 1.

Is this really caused the error on do_write_oneword by the changed?
Actually it was changed to use chip_good instead of chip_ready.
But before the change still do_write_oneword uses both chip_ready and 
chip_good.
So it seems that it is possible to be caused the error before the change 
also.

By the way could you please try to test the version 5 patches again?

Regards,
Ikegami

>
> Thanks,
> Ahmad
>
>
>>>> 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 at gmail.com>
>>>> Tested-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
>>>> Cc: stable at 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.
>> Yeah, unfortunately this driver does not use quirk flags and tends to
>> hide quirks behind bool functions like above
>>
>> Regards
>> Vignesh
>>
>