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

["Cédric Le Goater" <clg@kaod.org>]

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 ? 

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;