[PATCH 2/3] mmc: mmc: do not use CMD13 to get status after speed mode switch

[Ulf Hansson]

On 16 July 2016 at 00:10, Bjorn Andersson <bjorn.andersson at linaro.org> wrote:
> On Thu, May 19, 2016 at 1:47 AM, Chaotian Jing
> <chaotian.jing at mediatek.com> wrote:
>> Per JEDEC spec, it is not recommended to use CMD13 to get card status
>> after speed mode switch. below are two reason about this:
>> 1. CMD13 cannot be guaranteed due to the asynchronous operation.
>> Therefore it is not recommended to use CMD13 to check busy completion
>> of the timing change indication.
>> 2. After switch to HS200, CMD13 will get response of 0x800, and even the
>> busy signal gets de-asserted, the response of CMD13 is aslo 0x800.
>>
>> Signed-off-by: Chaotian Jing <chaotian.jing at mediatek.com>
>> ---
>>  drivers/mmc/core/mmc.c | 112 ++++++++++++++++++++-----------------------------
>>  1 file changed, 45 insertions(+), 67 deletions(-)
>>
>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> [..]
>> @@ -1274,20 +1254,18 @@ static int mmc_select_hs200(struct mmc_card *card)
>>                 err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>>                                    EXT_CSD_HS_TIMING, val,
>>                                    card->ext_csd.generic_cmd6_time,
>> -                                  true, send_status, true);
>> +                                  true, false, true);
>>                 if (err)
>>                         goto err;
>>                 old_timing = host->ios.timing;
>>                 mmc_set_timing(host, MMC_TIMING_MMC_HS200);
>> -               if (!send_status) {
>> -                       err = mmc_switch_status(card);
>> -                       /*
>> -                        * mmc_select_timing() assumes timing has not changed if
>> -                        * it is a switch error.
>> -                        */
>> -                       if (err == -EBADMSG)
>> -                               mmc_set_timing(host, old_timing);
>> -               }
>> +               err = mmc_switch_status(card);
>> +               /*
>> +                * mmc_select_timing() assumes timing has not changed if
>> +                * it is a switch error.
>> +                */
>> +               if (err == -EBADMSG)
>> +                       mmc_set_timing(host, old_timing);
>
> Sorry for not spotting this earlier, but with the move of the call of
> mmc_switch_status() to after mmc_set_timing() we get following error
> with sdhci-msm:

Thanks for reporting!

>
> mmc0: mmc_select_hs200 failed, error -110
> mmc0: error -110 whilst initialising MMC card
> mmc0: Reset 0x1 never completed.
> sdhci: =========== REGISTER DUMP (mmc0)===========
> sdhci: Sys addr: 0x00000000 | Version: 0x00002e02
> sdhci: Blk size: 0x00004000 | Blk cnt: 0x00000000
> sdhci: Argument: 0x00000000 | Trn mode: 0x00000000
> sdhci: Present: 0x01f80000 | Host ctl: 0x00000000
> sdhci: Power: 0x00000000 | Blk gap: 0x00000000
> sdhci: Wake-up: 0x00000000 | Clock: 0x00000003
> sdhci: Timeout: 0x00000000 | Int stat: 0x00000000
> sdhci: Int enab: 0x00000000 | Sig enab: 0x00000000
> sdhci: AC12 err: 0x00000000 | Slot int: 0x00000000
> sdhci: Caps: 0x322dc8b2 | Caps_1: 0x00008007
> sdhci: Cmd: 0x00000000 | Max curr: 0x00000000
> sdhci: Host ctl2: 0x00000000
> sdhci: ADMA Err: 0x00000000 | ADMA Ptr: 0x0000000000000000
> sdhci: ===========================================
>
> But I if I understand the commit correctly this is the intention of
> the patch (not the error, but the move).

I tried dropping this change from my next branch, but there are some
more changes on top that prevents a "clean" drop. It's certainly
doable, but perhaps we can try to narrow down the problem to see if
this could/should be fixed in the sdhci msm driver instead!?

I also noticed that below submitted change, which *isn't* applied for
next, might be related.
https://patchwork.kernel.org/patch/9197881/

>
> Regards,
> Bjorn
>
>>         }
>>  err:
>>         if (err)
>> --
>> 1.8.1.1.dirty
>>

Kind regards
Uffe