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

[Georgi Djakov <georgi.djakov@linaro.org>]

On 07/19/2016 12:31 PM, Ulf Hansson wrote:
> On 18 July 2016 at 15:38, Georgi Djakov <georgi.djakov@linaro.org> wrote:
>> On 07/18/2016 03:50 PM, Ulf Hansson wrote:
>>> On 16 July 2016 at 00:10, Bjorn Andersson <bjorn.andersson@linaro.org> wrote:
>>>> On Thu, May 19, 2016 at 1:47 AM, Chaotian Jing
>>>> <chaotian.jing@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@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!
> 

Here is a partial fix, as it resolves the issue for the eMMC only.
https://patchwork.kernel.org/patch/9237679/
More investigation ongoing.

Thanks,
Georgi

>>
>>>
>>> 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
>