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

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

On 7/22/20 10:02 AM, Cédric Le Goater wrote:
> 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)

FWIW QEMU models this one as 64KiB.

> 
> 
> I think we need a special case for it.
> 
> C. 
>