linux-kernel - Re: [PATCH] hibernation:stop resume screen during hibernation

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Message-ID: <CAJZ5v0gnYHmbWANVkoG+6XrUNzBB4__uM0Ladrpn5=L0KEiefA@mail.gmail.com>
Date:   Tue, 22 Jun 2021 15:06:31 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     pingshuo <pingshuo@...ontech.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] hibernation:stop resume screen during hibernation

On Tue, Jun 22, 2021 at 2:46 PM pingshuo <pingshuo@...ontech.com> wrote:
>
> The display will be woken up during hibernation.

That actually depends on its driver.

> if the computer equipment is poor, it will cause the screen to flicker.
> Skip to reusme the display devices in "thaw".

But this patch looks like a proof of concept rather than a proper solution.

This needs to be done more carefully.

> Signed-off-by: pingshuo <pingshuo@...ontech.com>
> ---
>  drivers/base/power/main.c | 43 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
>
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index f893c3c5af07..f3e92ac7b4b3 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -35,11 +35,14 @@
>  #include <linux/cpuidle.h>
>  #include <linux/devfreq.h>
>  #include <linux/timer.h>
> +#include <linux/pci.h>
>
>  #include "../base.h"
>  #include "power.h"
>
>  typedef int (*pm_callback_t)(struct device *);
> +#define VIDEO_PCI_CLASS 0x030000
> +#define VIDEO_PCI_CLASS_VALID 0xff0000
>
>  #define list_for_each_entry_rcu_locked(pos, head, member) \
>         list_for_each_entry_rcu(pos, head, member, \
> @@ -693,6 +696,40 @@ static void async_resume_noirq(void *data, async_cookie_t cookie)
>         put_device(dev);
>  }
>
> +/**
> + * dpm_resume_skip_display_devices - Skip to reusme the display devices.
> + * @dev: Device to handle.
> + * @state: PM transition of the system being carried out.
> + *
> + * Delete the display devices from the wake-up list during the "thaw".
> + */
> +static int dpm_resume_skip_display_devices(struct device *dev, pm_message_t state)
> +{
> +       struct pci_dev *pci_test = to_pci_dev(dev);

If you want to deal with PCI devices, that needs to happen at the PCI
bus type level in the first place.

> +
> +       if (state.event == PM_EVENT_THAW) {
> +               /*
> +                * Filter out the display devices
> +                */
> +               if ((pci_test && ((pci_test->class & VIDEO_PCI_CLASS_VALID) == VIDEO_PCI_CLASS)) ||
> +                       (dev->driver && dev->driver->name &&
> +                       strncmp(dev->driver->name, "video", 6) == 0)) {
> +
> +                       pr_info("Skip the display devices during the thaw.");
> +                       /*
> +                        * Remove the display devices from the resume stage
> +                        */
> +                       list_del(&dev->power.entry);
> +                       /*
> +                        * Remove the display devices from the power down stage
> +                        */
> +                       list_del(&dev->kobj.entry);
> +                       return 1;
> +               }
> +       }
> +       return 0;
> +}
> +
>  static void dpm_noirq_resume_devices(pm_message_t state)
>  {
>         struct device *dev;
> @@ -713,6 +750,10 @@ static void dpm_noirq_resume_devices(pm_message_t state)
>         while (!list_empty(&dpm_noirq_list)) {
>                 dev = to_device(dpm_noirq_list.next);
>                 get_device(dev);
> +
> +               if (dpm_resume_skip_display_devices(dev, state))
> +                       continue;
> +
>                 list_move_tail(&dev->power.entry, &dpm_late_early_list);
>                 mutex_unlock(&dpm_list_mtx);
>
> @@ -737,6 +778,8 @@ static void dpm_noirq_resume_devices(pm_message_t state)
>         trace_suspend_resume(TPS("dpm_resume_noirq"), state.event, false);
>  }
>
> +
> +
>  /**
>   * dpm_resume_noirq - Execute "noirq resume" callbacks for all devices.
>   * @state: PM transition of the system being carried out.
> --