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

[Guenter Roeck]

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.

Thanks,
Guenter

> Thanks,
> 
> C. 
> 
> 
> diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
> index 8227088441..5000930800 100644
> --- a/hw/block/m25p80.c
> +++ b/hw/block/m25p80.c
> @@ -1041,7 +1041,7 @@ static void decode_new_cmd(Flash *s, uint32_t value)
>              s->data[i] = s->pi->id[i];
>          }
>          for (; i < SPI_NOR_MAX_ID_LEN; i++) {
> -            s->data[i] = 0;
> +            s->data[i] = s->pi->id[i % s->pi->id_len];
>          }
> 
>          s->len = SPI_NOR_MAX_ID_LEN;
>