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

[Pratyush Yadav <ptyadav@amazon.de>]

On Tue, Jan 24 2023, Dhruva Gole wrote:

> On 24/01/23 16:13, Pratyush Yadav wrote:
>> 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.
> Yes, I believe 8D-8D-8D is being used.
> Here's the output:
> ...
> root@am62xx-evm:~# cat /sys/kernel/debug/spi-nor/spi0.0/params
> name            s28hs512t
> id              34 5b 1a 0f 03 90
> size            64.0 MiB
> write size      16
> page size       256
> address nbytes  4
> flags           4B_OPCODES | HAS_4BAIT | HAS_16BIT_SR | IO_MODE_EN_VOLATILE | SOFT_RESET
>
> opcodes
>  read           0xee
>   dummy cycles  24
>  erase          0xd8
>  program        0x12
>  8D extension   repeat
>
> protocols
>  read           8D-8D-8D
>  write          8D-8D-8D
>  register       8D-8D-8D
>
> erase commands
>  21 (4.00 KiB) [2]
>  dc (256 KiB) [3]
>  c7 (64.0 MiB)
>
> sector map
>  region (in hex)   | erase mask | flags
>  ------------------+------------+----------
>  00000000-0001ffff |     [  2 ] |
>  00020000-0003ffff |     [   3] | overlaid
>  00040000-03ffffff |     [   3] |
> ...
>
> Also, the raw read speed is about 40 MBPS
> The frequency we set from DT is 25 MHz,
> assuming 1MB is transfered every cycle's rising and falling edge,
> ie. 25*2 = 50 MBPS is ideal speed.

Yep, that's what I would expect as well. Thanks for confirming.

>
>>
>> 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. */
>
> --
> Best regards,
> Dhruva Gole
> Texas Instruments Incorporated
>

-- 
Regards,
Pratyush Yadav



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