Re: [PATCH v1 2/4] acpi/x86: s2idle: handle screen off/on calls outside of suspend sequence

[Mario Limonciello <mario.limonciello@amd.com>]

+dri-devel

For those joining late; this is the full series for context.

https://lore.kernel.org/linux-pm/20240919171952.403745-1-lkml@antheas.dev/T/#maee308be5349d8df25c8ccf12144ea96bbd4cbbd

On 9/19/2024 12:19, Antheas Kapenekakis wrote:
> Currently, the screen off/on calls are handled within the suspend
> sequence, which is a deviation from Windows. This causes issues with
> certain devices, such as the ROG Ally, which expects this call to be
> executed with the kernel fully awake. The subsequent half-suspended
> state makes the controller of the device to fail to suspend properly.
> 
> This patch calls the screen off/on callbacks before entering the suspend
> sequence, which fixes this issue. In addition, it opens the possibility
> of modelling a state such as "Screen Off" that mirrors Windows, as the
> callbacks will be accessible and validated to work outside of the
> suspend sequence.
> 
> Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
> ---
>   kernel/power/suspend.c | 16 ++++++++++++++++
>   1 file changed, 16 insertions(+)
> 
> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> index 19734b297527..afa95271ef00 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -507,6 +507,19 @@ int suspend_devices_and_enter(suspend_state_t state)
>   
>   	pm_suspend_target_state = state;
>   
> +	/*
> +	 * Linux does not have the concept of a "Screen Off" state, so call
> +	 * the platform functions for screen off prior to beginning the suspend
> +	 * sequence, mirroring Windows which calls them outside of it as well.
> +	 *
> +	 * If Linux ever gains a "Screen Off" state, the following callbacks can
> +	 * be replaced with a call that checks if we are in "Screen Off", in which
> +	 * case they will NOOP and if not call them as a fallback.
> +	 */
> +	error = platform_suspend_screen_off();

It's a bit muddy; but I wonder if calling 
drm_atomic_helper_disable_all() makes sense here.

> +	if (error)
> +		goto Screen_on;
> +
>   	if (state == PM_SUSPEND_TO_IDLE)
>   		pm_set_suspend_no_platform();
>   
> @@ -540,6 +553,9 @@ int suspend_devices_and_enter(suspend_state_t state)
>    Close:
>   	platform_resume_end(state);
>   	pm_suspend_target_state = PM_SUSPEND_ON;
> +
> + Screen_on:
> +	platform_suspend_screen_on();

The problem with my suggestion above is what would you put here for 
symmetry?  drm_atomic_helper_resume() doesn't look right to me.

Maybe it's a no-op from DRM perspective and the drivers handle it.

>   	return error;
>   
>    Recover_platform: