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

[Georgi Djakov]

On 07/18/2016 03:50 PM, Ulf Hansson wrote:
> On 16 July 2016 at 00:10, Bjorn Andersson <bjorn.andersson@xxxxxxxxxx> wrote:
>> On Thu, May 19, 2016 at 1:47 AM, Chaotian Jing
>> <chaotian.jing@xxxxxxxxxxxx> 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@xxxxxxxxxxxx>
>>> ---
>>>  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.

> 
> 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.

Thanks,
Georgi