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

[Ulf Hansson]

On 18 July 2016 at 15:38, Georgi Djakov <georgi.djakov at linaro.org> wrote:
> On 07/18/2016 03:50 PM, Ulf Hansson wrote:
>> 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!?
>
> Yes, i am working on it. Seems that if we just ignore the -ETIMEDOUT
> returned by mmc_switch_status() everything works as before. Currently
> i am expecting more information about this controller specifics, in
> order to understand if this could be fixed with a change in the driver
> only.

Thanks for looking into this!

>
>>
>> I also noticed that below submitted change, which *isn't* applied for
>> next, might be related.
>> https://patchwork.kernel.org/patch/9197881/
>>
>
> It is not related to this issue, but it is good to have when this is
> resolved, otherwise we will see the dumpregs output (pr_err now),
> when controller is initialized without a card in the SD slot.

Okay, thanks for clarifying. Although, I need an ack from Adrian
before I apply it.

>
> Thanks,
> Georgi

Kind regards
Uffe