Re: [PATCH 1/2] mtd: spi-nor: spansion: Consider reserved bits in CFR5 register

[Pratyush Yadav <ptyadav@amazon.de>]

On Mon, Jan 23 2023, Dhruva Gole wrote:

> Hi Pratyush,
>
> On 23/01/23 20:07, Pratyush Yadav wrote:
>> +Cc Dhruva
> I had already reviewed this, but now I have locally applied the patches,
> to linux master and built and tested - seems okay,
>> Hi Tudor,
>>
>> On Tue, Jan 10 2023, Tudor Ambarus wrote:
>>
>>> CFR5[6] is reserved bit and must be always 1. Set it to comply with flash
>>> requirements. While fixing SPINOR_REG_CYPRESS_CFR5V_OCT_DTR_{EN, DS}
>>> definition, stop using magic numbers and describe the missing bit fields
>>> in CFR5 register. This is useful for both readability and future possible
>>> addition of Octal STR mode support.
>>>
>>> Fixes: c3266af101f2 ("mtd: spi-nor: spansion: add support for Cypress Semper flash")
>>> Cc: stable@vger.kernel.org
>>> Reported-by: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>
>>> Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
>>> ---
>>>  drivers/mtd/spi-nor/spansion.c | 9 +++++++--
>>>  1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/mtd/spi-nor/spansion.c b/drivers/mtd/spi-nor/spansion.c
>>> index b621cdfd506f..07fe0f6fdfe3 100644
>>> --- a/drivers/mtd/spi-nor/spansion.c
>>> +++ b/drivers/mtd/spi-nor/spansion.c
>>> @@ -21,8 +21,13 @@
>>>  #define SPINOR_REG_CYPRESS_CFR3V               0x00800004
>>>  #define SPINOR_REG_CYPRESS_CFR3V_PGSZ          BIT(4) /* Page size. */
>>>  #define SPINOR_REG_CYPRESS_CFR5V               0x00800006
>>> -#define SPINOR_REG_CYPRESS_CFR5V_OCT_DTR_EN    0x3
>>> -#define SPINOR_REG_CYPRESS_CFR5V_OCT_DTR_DS    0
>>> +#define SPINOR_REG_CYPRESS_CFR5_BIT6           BIT(6)
>> Perhaps comment here that this bit is reserved. Otherwise it is not
>> obvious what this does and why we are setting it without going through
>> git-blame. No need for a re-roll, I think it is fine if you add this
>> when applying.
>>
>>> +#define SPINOR_REG_CYPRESS_CFR5_DDR            BIT(1)
>>> +#define SPINOR_REG_CYPRESS_CFR5_OPI            BIT(0)
>>> +#define SPINOR_REG_CYPRESS_CFR5V_OCT_DTR_EN                            \
>>> +       (SPINOR_REG_CYPRESS_CFR5_BIT6 | SPINOR_REG_CYPRESS_CFR5_DDR |   \
>>> +        SPINOR_REG_CYPRESS_CFR5_OPI)
>>> +#define SPINOR_REG_CYPRESS_CFR5V_OCT_DTR_DS    SPINOR_REG_CYPRESS_CFR5_BIT6
>> I would say don't fix what isn't broken. But if you do, test it. Do you
>> or Takahiro have a Cypress S28* flash to test this change on? If no,
>> then perhaps Dhruva can help here since TI uses this flash on a bunch of
>> their boards?
>>
>> The change looks fine to me with the above comment added, I just would
>> like someone to test it once.
> Tested OSPI_S_FUNC_DD_RW_ERASESIZE_UBIFS from ltp-ddt and test seemed to pass on my
> AM625 SK EVM having an OSPI NOR S28HS512T Flash.

Thanks.

BTW, one interesting bit about this in case you didn't know already.
Since this is playing with Octal DTR enable/disable, you might also want
to double-check you are actually using Octal DTR mode. This can be done
by looking at the SPI NOR debugfs entry (usually in
/sys/kernel/debug/spi-nor). You can "cat params" and see what protocols
are being used, and make sure 8D-8D-8D is being used.

AM625 SK _should_ be using 8D-8D-8D mode already, but I think it is
useful if you know how to confirm this assumption :-)

>>
>> Reviewed-by: Pratyush Yadav <ptyadav@amazon.de>
> For this series,
>
> Tested-by: Dhruva Gole <d-gole@ti.com>
>
>>>  #define SPINOR_OP_CYPRESS_RD_FAST              0xee
>>>
>>>  /* Cypress SPI NOR flash operations. */

-- 
Regards,
Pratyush Yadav



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