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

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Message-ID: <CANYu_0t5uRk0p=+4S9e3oCOy=gQ6rS2bqmAUqmkd7FVxsxywJw@mail.gmail.com>
Date:   Fri, 23 Sep 2016 11:56:48 +0530
From:   Pramod Gurav <pramod.gurav@...aro.org>
To:     Ritesh Harjani <riteshh@...eaurora.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        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>,
        Stephen Boyd <sboyd@...eaurora.org>
Subject: Re: [PATCH v3] mmc: sdhci-msm: Add pm_runtime and system PM support

Hi Ritesh,

Thanks for the inputs.

On 22 September 2016 at 20:02, Ritesh Harjani <riteshh@...eaurora.org> wrote:
> Hi Pramod,

<snip>

>> 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.

Honestly I took reference from existing SDHCI HC driver which
implement the runtime PM and each one uses this function.

>
> 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.
This should work as I did not have this funtion call in my V1 but
later included when I referred the other sdhci drivers.

>
>
> 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.
This seems a read only register. And I could not find any other
reference of this mode in any of the docs.
>
>>
>> Regards,
>> Pramod
>>
>