Re: [RFC PATCH 1/7] mmc: sdhci: Add quirk to indicate no CRC stripping in MMC_RSP_136

Kishon Vijay Abraham I
2017-08-17T07:40:14Z

On Thursday 17 August 2017 12:01 PM, Adrian Hunter wrote:
> On 17/08/17 08:20, Kishon Vijay Abraham I wrote:
>> Hi Adrian,
>>
>> On Tuesday 15 August 2017 12:57 PM, Adrian Hunter wrote:
>>> On 07/08/17 19:01, Kishon Vijay Abraham I wrote:
>>>> TI's implementation of sdhci controller used in DRA7 SoC's doesn't
>>>> strip CRC in responses with length 136 bits. Add quirk to indicate
>>>> the controller does not strip CRC in MMC_RSP_136. If this quirk is
>>>> set sdhci library shouldn't shift the response present in
>>>> SDHCI_RESPONSE register.
>>>>
>>>> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
>>>> ---
>>>> drivers/mmc/host/sdhci.c | 27 +++++++++++++++++++--------
>>>> drivers/mmc/host/sdhci.h | 2 ++
>>>> 2 files changed, 21 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>>>> index ecd0d4350e8a..ece3751d2a25 100644
>>>> --- a/drivers/mmc/host/sdhci.c
>>>> +++ b/drivers/mmc/host/sdhci.c
>>>> @@ -1182,14 +1182,25 @@ static void sdhci_finish_command(struct sdhci_host *host)
>>>>
>>>> if (cmd->flags & MMC_RSP_PRESENT) {
>>>> if (cmd->flags & MMC_RSP_136) {
>>>> - /* CRC is stripped so we need to do some shifting. */
>>>> - for (i = 0;i < 4;i++) {
>>>> - cmd->resp[i] = sdhci_readl(host,
>>>> - SDHCI_RESPONSE + (3-i)*4) << 8;
>>>> - if (i != 3)
>>>> - cmd->resp[i] |=
>>>> - sdhci_readb(host,
>>>> - SDHCI_RESPONSE + (3-i)*4-1);
>>>> + if (!(host->quirks2 & SDHCI_QUIRK2_NO_CRC_STRIPPING)) {
>>>
>>> This is about the 136-bit response so let's put that in the quirk name. How about SDHCI_QUIRK2_RSP_136_HAS_CRC
>>
>> Since omap seems to be the only platform that doesn't have CRC, I prefer adding
>> SDHCI_QUIRK2_RSP_136_NO_CRC. That way we can add the quirk only in sdhci-omap
>> instead of all the existing sdhci drivers.
>
> Except that it is the way I described. All the others strip the CRC and we
> have to shift to pretend it is still there.

right. I made a totally bogus statement.

Thanks
Kishon