Re: [PATCH] mmc: block: Dont report successful writes with errors

[Adrian Hunter <adrian.hunter@intel.com>]

On 29/07/22 17:20, Christian Loehle wrote:
> 
>>> If not I would at least add the !mmc_is_host_spi condition for calling mmc_blk_status_error to make it a bit more clear that this function does do what is intended for SPI cards.
>>
>> I am not sure what you mean.  Isn't it OK to check CMD13 response for SPI?
> 
> You can do that for sure, but e.g. without some knowledge about what state you're in it doesn't tell you a lot.
> If you get all zeroes after a write e.g., you cannot always tell if the SPI card is holding the line LOW because of busy[*], or you actually got an SPI R2 with no error bits set. (The CMD12 = ILLEGAL assert would fix it, but now all cards behave this way and the spec doesn't mandate it.)
> It cannot really be dealt with in a nice manner.
> Furthermore cards are, according to spec, free to treat cmd13 as ILLEGAL during data state.
> If so, that's nice for us, we get a 0x4 back and know we have to fix state, some cards also
> accept CMD13 (no error bits set), perfectly legal, but we don't know if we should fix state or not.
> (Furthermore, how to fix state is then dependent on the issued (e.g. timedout command)
> 
> *The SD SPI spec e.g. says in 7.2.8 that a CMD13 must ALWAYS be responded to, but that is clearly not the intention of the spec, a card always listening for CMD13 in RCV state simply doesn't make sense.

Note, my comments were structural, not functional:
	- use mmc_blk_status_error() to check the status only, since that is what that function is for,
	- make the brq->data.error check a separate patch since it needs its own explanation

WRT getting SPI error handling to work the way you need, that is up to you,
so long as there is a reasonable explanation.