Re: [PATCH v2 2/4] m25p80: Improve command handling for Jedec commands

["Cédric Le Goater" <clg@kaod.org>]

On 7/21/20 9:57 PM, Guenter Roeck wrote:
> On 7/21/20 10:36 AM, Cédric Le Goater wrote:
>> Hello,
>>
>> On 2/6/20 7:32 PM, Guenter Roeck wrote:
>>> When requesting JEDEC data using the JEDEC_READ command, the Linux kernel
>>> always requests 6 bytes. The current implementation only returns three
>>> bytes, and interprets the remaining three bytes as new commands.
>>> While this does not matter most of the time, it is at the very least
>>> confusing. To avoid the problem, always report up to 6 bytes of JEDEC
>>> data. Fill remaining data with 0.
>>>
>>> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>>> ---
>>> v2: Split patch into two parts; improved decription
>>>
>>>  hw/block/m25p80.c | 5 ++++-
>>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
>>> index 5ff8d270c4..53bf63856f 100644
>>> --- a/hw/block/m25p80.c
>>> +++ b/hw/block/m25p80.c
>>> @@ -1040,8 +1040,11 @@ static void decode_new_cmd(Flash *s, uint32_t value)
>>>          for (i = 0; i < s->pi->id_len; i++) {
>>>              s->data[i] = s->pi->id[i];
>>>          }
>>> +        for (; i < SPI_NOR_MAX_ID_LEN; i++) {
>>> +            s->data[i] = 0;
>>> +        }
>>
>> This is breaking an old firmware (Linux version 2.6.28.9) for a SuperMicro
>> board : 
>>
>> 	https://www.supermicro.com/en/products/motherboard/X11SSL-F 
>>
>> which expects the flash ID to repeat. Erik solved the problem with the patch 
>> below and I think it makes sense to wrap around. Anyone knows what should be 
>> the expected behavior ? 
>>
> 
> No idea what the expected behavior is, but I am fine with the code below
> if it works.

I checked on a few real systems and indeed the mx25l25635e behaves
differently.

AST2400

[    5.594176] aspeed-smc 1e620000.spi: reading JEDEC ID 20:BA:19:10:00:00
[    5.602226] aspeed-smc 1e620000.spi: n25q256a (32768 Kbytes)
...
[    6.174052] aspeed-smc 1e630000.spi: reading JEDEC ID C2:20:19:C2:20:19
[    6.181682] aspeed-smc 1e630000.spi: mx25l25635e (32768 Kbytes)

AST2500

[    1.641317] aspeed-smc 1e620000.spi: reading JEDEC ID EF:40:19:00:00:00
[    1.648174] aspeed-smc 1e620000.spi: w25q256 (32768 Kbytes)
...
[    1.179214] aspeed-smc 1e630000.spi: reading JEDEC ID EF:40:19:00:00:00
[    1.186737] aspeed-smc 1e630000.spi: w25q256 (32768 Kbytes)

AST2600

[    1.020255] aspeed-smc 1e620000.spi: reading JEDEC ID EF:40:20:00:00:00
[    1.027830] aspeed-smc 1e620000.spi: w25q512jv (65536 Kbytes)
...
[    1.884171] aspeed-smc 1e630000.spi: reading JEDEC ID EF:40:19:00:00:00
[    1.890937] aspeed-smc 1e630000.spi: w25q256 (32768 Kbytes)


I think we need a special case for it.

C.