Re: [PATCH v3] mmc: sdhci-msm: Add pm_runtime and system PM support

[Ritesh Harjani]

Hi Pramod,

On 9/15/2016 7:28 PM, Pramod Gurav wrote:
> On 15 September 2016 at 15:49, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> > On 15 September 2016 at 09:59, Pramod Gurav <pramod.gurav@xxxxxxxxxx> wrote:
> > > On 9 September 2016 at 15:48, Georgi Djakov <georgi.djakov@xxxxxxxxxx> 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@xxxxxxxxxx>
> > > > >
> > > > >
> > > > > 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@xxxxxxx>
> > > 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?
> Thanks Ulf for the comments. Will check this and see if there is
> something of this sort we have to do to achieve auto tuning.
> Adding Ritesh who has been posting some SDHCI MSM patches recently in
> case he knows about this.

Internally, we don't use this Auto re-tuning and rely on explicit 
re-tune by host driver.

Question though -
1. why do we need to call sdhci_runtime_resume/suspend from 
sdhci_msm_runtime_suspend/resume?
From what I see is, sdhci_runtime_susend/resume will do reset and 
re-program of host->pwr and host->clk because of which a retune will be 
required for the next command after runtime resume.

We can *only* disable and enable the clocks in 
sdhci_msm_runtime_suspend/resume?
Thoughts? With this, I suppose you would not see any issue.


Though for this issue, since internally also auto retuning is never 
used, we can have this mode disabled. I can once again check with HW 
team to get more details about this mode for MSM controller.

> Regards,
> Pramod