linux-kernel - Re: [PATCH v3] mmc: sdhci-msm: Add pm

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Date:   Thu, 15 Sep 2016 12:19:25 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Pramod Gurav <pramod.gurav@...aro.org>
Cc:     Georgi Djakov <georgi.djakov@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        "open list:ARM/QUALCOMM SUPPORT" <linux-arm-msm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Ritesh Harjani <riteshh@...eaurora.org>,
        Stephen Boyd <sboyd@...eaurora.org>
Subject: Re: [PATCH v3] mmc: sdhci-msm: Add pm_runtime and system PM support

On 15 September 2016 at 09:59, Pramod Gurav <pramod.gurav@...aro.org> wrote:
> On 9 September 2016 at 15:48, Georgi Djakov <georgi.djakov@...aro.org> wrote:
>> On 09/08/2016 11:02 AM, Adrian Hunter wrote:
>>>
>>> On 01/09/16 17:23, Pramod Gurav wrote:
>>>>
>>>> Provides runtime PM callbacks to enable and disable clock resources
>>>> when idle. Also support system PM callbacks to be called during system
>>>> suspend and resume.
>>>>
>>>> Signed-off-by: Pramod Gurav <pramod.gurav@...aro.org>
>>>
>>>
>>> Can we get some Tested/Reviewed/Acked-by from people using this driver?
>>>
>>
>> Hi Pramod,
>> Thanks for the patch. Unfortunately, my db410c board fails to
>> boot when i apply it.
>>
>
> Thanks Georgi for testing the patch. Its my wrong I did not update my
> kernel and continued fixing comments on old kernel.
> After spending some time I came to know that below change is causing the issue:
>
> Author: Dong Aisheng <aisheng.dong@....com>
> Date:   Tue Jul 12 15:46:17 2016 +0800
>
>     mmc: sdhci: add standard hw auto retuning support
>
>     If HW supports SDHCI_TUNING_MODE_3 which is auto retuning, we won't
>     retune during runtime suspend and resume, instead we use Re-tuning
>     Request signaled via SDHCI_INT_RETUNE interrupt to do retuning and
>     hw auto retuning during data transfer to guarantee the signal sample
>     window correction.
>
>     This can avoid a mass of repeatedly retuning during small file system
>     data access and improve the performance.
>
> Specially these lines that was added to suspend path:
>
> +       if (host->tuning_mode != SDHCI_TUNING_MODE_3)
> +               mmc_retune_needed(host->mmc);
>
> During sdhci setup in msm driver, the host returns the values to set
> sdhci auto tuning as supported.
> Hence host->tuning_mode is set to SDHCI_TUNING_MODE_3 during setup.
> But some how the auto tuning is not happening.
> Just to verify my case, I removed the 'if' part in above code and got
> the FS mounted.
>
> Is there anything else needed in msm sdhci driver so that the auto
> tuning is taken care of?

I am not familiar with any other than sdhci-esdhc-imx which supports
the SDHCI_TUNING_MODE_3. I may be wrong though.

In the sdhci-esdhc-imx case, enabling of auto tuning seems to be done
in esdhc_post_tuning(), where a vendor specific register
(ESDHC_MIX_CTRL) is being written to. Perhaps something similar in
your case?

[...]

Kind regards
Uffe