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Re: [PATCH] hw/sd: sd: Bypass the RCA check for CMD13 in SPI mode

From: Philippe Mathieu-Daudé
Subject: Re: [PATCH] hw/sd: sd: Bypass the RCA check for CMD13 in SPI mode
Date: Mon, 8 Feb 2021 14:08:49 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0

On 1/30/21 11:20 AM, Bin Meng wrote:
> Hi Philippe,
> On Fri, Jan 29, 2021 at 10:11 PM Philippe Mathieu-Daudé <f4bug@amsat.org> 
> wrote:
>> Hi Bin,
>> On 1/29/21 9:51 AM, Bin Meng wrote:
>>> From: Bin Meng <bin.meng@windriver.com>
>>> Unlike SD mode, when SD card is working in SPI mode, the argument
>>> of CMD13 is stuff bits. Hence we should bypass the RCA check.
>> Is this for detecting events by polling? From spec v8:
>>   5.7.5 Event Indication Method
>> FX_EVENT (Bit06 of Card Status)
>>     An event indication method is introduced from Version 4.20.
>>     Card may use Bit06 of R1 (R1b) response of any SD command
>>     to indicate event generation.
>>   F.2 Concept of Event Detection Method
>>   F.2.2 Host Implementation to use Event Detection Method
> I think you looked at the wrong place. See spec v8
> chapter Detailed Command Description
> "The card shall ignore stuff bits and reserved bits in an argument"
> and Table 7-3 Commands and Arguments
> CMD13 Argument [31:0] stuff bits

Indeed. Adding this information in the commit description makes
things obvious ;)

The SPI responses are not well implemented, in this case (CMD13)
it is incorrect, we should return a 2-byte R2. Your patch
correctly skip the RCA check, but we still invalid data.

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