linux-kernel - Re: [PATCH V4] mmc: sdhci-msm: Update system suspend/resume callbacks of sdhci-msm platform driver

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Date:   Thu, 5 Mar 2020 19:26:54 +0530
From:   Veerabhadrarao Badiganti <vbadigan@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.org>,
        Shaik Sajida Bhanu <sbhanu@...eaurora.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Asutosh Das <asutoshd@...eaurora.org>,
        Sahitya Tummala <stummala@...eaurora.org>,
        Sayali Lokhande <sayalil@...eaurora.org>, cang@...eaurora.org,
        Ram Prakash Gupta <rampraka@...eaurora.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH V4] mmc: sdhci-msm: Update system suspend/resume callbacks
 of sdhci-msm platform driver


On 3/4/2020 10:16 PM, Stephen Boyd wrote:
> Quoting Ulf Hansson (2020-03-04 07:34:29)
>> On Thu, 20 Feb 2020 at 07:45, Shaik Sajida Bhanu <sbhanu@...eaurora.org> wrote:
>>> The existing suspend/resume callbacks of sdhci-msm driver are just
>>> gating/un-gating the clocks. During suspend cycle more can be done
>>> like disabling controller, disabling card detection, enabling wake-up events.
>>>
>>> So updating the system pm callbacks for performing these extra
>>> actions besides controlling the clocks.
>>>
>>> Signed-off-by: Shaik Sajida Bhanu <sbhanu@...eaurora.org>
>>> Reviewed-by: Stephen Boyd <swboyd@...omium.org>
>>> ---
>>> Changes since V3:
>>>      Invoking sdhci & cqhci resume if sdhci_host_suspend fails.
>>>      Removed condition check before invoking cqhci_resume since its a dummy function.
>>>
>>> Changes since V2:
>>>      Removed disabling/enabling pwr-irq from system pm ops.
>>>
>>> Changes since V1:
>>>      Invoking pm_runtime_force_suspend/resume instead of
>>>      sdhci_msm_runtime_suepend/resume.
>>> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
>>> index 3955fa5d..3559b50 100644
>>> --- a/drivers/mmc/host/sdhci-msm.c
>>> +++ b/drivers/mmc/host/sdhci-msm.c
>>> @@ -2159,9 +2159,52 @@ static __maybe_unused int sdhci_msm_runtime_resume(struct device *dev)
> [...]
>>> +
>>> +       ret = sdhci_suspend_host(host);
>>> +       if (ret)
>>> +               goto resume_cqhci;
>> sdhci_suspend_host() can't be called on a device that has been runtime
>> suspended, as that would lead to accessing device registers when
>> clocks/PM domains are gated.
>>
>> Depending on how the corresponding cqhci device is managed from a
>> runtime PM point of view, it could also be problematic to call
>> cqhci_suspend().
> There seems to be another patch floating around here[1] that is an
> attempt at a fix to this patch. They should probably be combined so that
> it's not confusing what's going on.

The other fix is altogether different. It is the fix for the issue seen 
with run-time pm.

whereas this change is for system pm.

>>> +
>>> +       ret = pm_runtime_force_suspend(dev);
>> It looks to me that perhaps you could make use of solely
>> pm_runtime_force_suspend(), then just skip calling
>> sdhci_suspend|resume_host() altogether. Do you think that could work?
> Does that do all the things the commit text mentions is desired for
> system suspend?
>
>>> like disabling controller, disabling card detection, enabling wake-up events.
> [1] https://lore.kernel.org/linux-arm-msm/1583322863-21790-1-git-send-email-vbadigan@codeaurora.org/