Re: [PATCH] EmbeddedPkg/MmcDxe: Correct argument of ECSD read

[Jun Nie <jun.nie@linaro.org>]

2017-06-29 20:09 GMT+08:00 Leif Lindholm <leif.lindholm@linaro.org>:
> On Thu, Jun 29, 2017 at 05:02:05PM +0800, Jun Nie wrote:
>> The argument of CMD8 should be stuff bits according to standard
>> JESD84-A44.
>
> OK, I realise that "stuff bits" is a term used by the spec, so that is
> probably sufficient explanation even though the term was known to me.
> And the MdeModulePkg driver seems to agree on the technical point.
> My question is why zeroes is the correct "stuff bits" value?

Yes, it is defined in page 2 in spec. I guess 0 is best filling value
than other value when we do not need a real value.
stuff bit: filling 0 bits to ensure fixed length frames for commands
and responses.

>
>> Contributed-under: TianoCore Contribution Agreement 1.0
>> Signed-off-by: Jun Nie <jun.nie@linaro.org>
>> ---
>>  EmbeddedPkg/Universal/MmcDxe/MmcIdentification.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/EmbeddedPkg/Universal/MmcDxe/MmcIdentification.c b/EmbeddedPkg/Universal/MmcDxe/MmcIdentification.c
>> index 4ce0ddd..c28207e 100644
>> --- a/EmbeddedPkg/Universal/MmcDxe/MmcIdentification.c
>> +++ b/EmbeddedPkg/Universal/MmcDxe/MmcIdentification.c
>> @@ -210,7 +210,7 @@ EmmcIdentificationMode (
>>    }
>>
>>    // Fetch ECSD
>> -  Status = Host->SendCommand (Host, MMC_CMD8, RCA);
>> +  Status = Host->SendCommand (Host, MMC_CMD8, 0);
>>    if (EFI_ERROR (Status)) {
>>      DEBUG ((EFI_D_ERROR, "EmmcIdentificationMode(): ECSD fetch error, Status=%r.\n", Status));
>>    }
>> --
>> 1.9.1
>>