Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <1629732470-155444-1-git-send-email-psodagud@codeaurora.org>
In-Reply-To: <1629732470-155444-1-git-send-email-psodagud@codeaurora.org>
From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Fri, 27 Aug 2021 14:19:58 +0200
Message-ID: <CAJZ5v0hAuZmaB6j4qA7P43J4TshBrYa8UsX3KtH7hkxWZPU2wA@mail.gmail.com>
Subject: Re: [PATCH v4] PM: sleep: core: Avoid setting power.must_resume to false
To:     Prasad Sodagudi <psodagud@codeaurora.org>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Len Brown <len.brown@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        Pavel Machek <pavel@ucw.cz>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Mon, Aug 23, 2021 at 5:28 PM Prasad Sodagudi <psodagud@codeaurora.org> wrote:
>
> There are variables(power.may_skip_resume and dev->power.must_resume)
> and DPM_FLAG_MAY_SKIP_RESUME flags to control the resume of devices after
> a system wide suspend transition.
>
> Setting the DPM_FLAG_MAY_SKIP_RESUME flag means that the driver allows
> its "noirq" and "early" resume callbacks to be skipped if the device
> can be left in suspend after a system-wide transition into the working
> state. PM core determines that the driver's "noirq" and "early" resume
> callbacks should be skipped or not with dev_pm_skip_resume() function by
> checking power.may_skip_resume variable.
>
> power.must_resume variable is getting set to false in __device_suspend()
> function without checking device's DPM_FLAG_MAY_SKIP_RESUME settings.
> In problematic scenario, where all the devices in the suspend_late
> stage are successful and some device can fail to suspend in
> suspend_noirq phase. So some devices successfully suspended in suspend_late
> stage are not getting chance to execute __device_suspend_noirq()
> to set dev->power.must_resume variable to true and not getting
> resumed in early_resume phase.
>
> Add a check for device's DPM_FLAG_MAY_SKIP_RESUME flag before
> setting power.must_resume variable in __device_suspend function.
>
> Fixes: 6e176bf8d461 ("PM: sleep: core: Do not skip callbacks in the resume phase")
> Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>
> ---
>  V3 -> V4: Remove dev->power.usage_count variable check
>  V2 -> V3: Format issues patch posting
>  V1 -> V2: Fixed indentation and commit text to include scenario
>  drivers/base/power/main.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index d568772..50e8ea3 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -1642,7 +1642,10 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
>         }
>
>         dev->power.may_skip_resume = true;
> -       dev->power.must_resume = false;
> +       if (dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME))
> +               dev->power.must_resume = false;
> +       else
> +               dev->power.must_resume = true;

Why don't you write it as

dev->power.must_resume = !dev_pm_test_driver_flags(dev,
DPM_FLAG_MAY_SKIP_RESUME);

>
>         dpm_watchdog_set(&wd, dev);
>         device_lock(dev);
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>