Re: [PATCH v8 4/8] drm/i915: Do not call drm_crtc_arm_vblank_event in async flips

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Karthik B S <karthik.b.s@intel.com>
Cc: paulo.r.zanoni@intel.com, michel@daenzer.net,
	dri-devel@lists.freedesktop.org, nicholas.kazlauskas@amd.com,
	vandita.kulkarni@intel.com, uma.shankar@intel.com,
	daniel.vetter@intel.com, intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH v8 4/8] drm/i915: Do not call drm_crtc_arm_vblank_event in async flips
Date: Tue, 15 Sep 2020 17:07:19 +0300	[thread overview]
Message-ID: <20200915140719.GK6112@intel.com> (raw)
In-Reply-To: <20200914055633.21109-5-karthik.b.s@intel.com>

On Mon, Sep 14, 2020 at 11:26:29AM +0530, Karthik B S wrote:
> Since the flip done event will be sent in the flip_done_handler,
> no need to add the event to the list and delay it for later.
> 
> v2: -Moved the async check above vblank_get as it
>      was causing issues for PSR.
> 
> v3: -No need to wait for vblank to pass, as this wait was causing a
>      16ms delay once every few flips.
> 
> v4: -Rebased.
> 
> v5: -Rebased.
> 
> v6: -Rebased.
> 
> v7: -No need of irq disable if we are not doing vblank evade. (Ville)
> 
> v8: -Rebased.
> 
> Signed-off-by: Karthik B S <karthik.b.s@intel.com>
> Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_sprite.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_sprite.c b/drivers/gpu/drm/i915/display/intel_sprite.c
> index 5ac0dbf0e03d..f0c89418d2e1 100644
> --- a/drivers/gpu/drm/i915/display/intel_sprite.c
> +++ b/drivers/gpu/drm/i915/display/intel_sprite.c
> @@ -93,6 +93,9 @@ void intel_pipe_update_start(const struct intel_crtc_state *new_crtc_state)
>  	DEFINE_WAIT(wait);
>  	u32 psr_status;
>  
> +	if (new_crtc_state->uapi.async_flip)
> +		return;
> +
>  	vblank_start = adjusted_mode->crtc_vblank_start;
>  	if (adjusted_mode->flags & DRM_MODE_FLAG_INTERLACE)
>  		vblank_start = DIV_ROUND_UP(vblank_start, 2);
> @@ -202,6 +205,9 @@ void intel_pipe_update_end(struct intel_crtc_state *new_crtc_state)
>  
>  	trace_intel_pipe_update_end(crtc, end_vbl_count, scanline_end);
>  
> +	if (new_crtc_state->uapi.async_flip)
> +		return;

The pipe update tracepoints will be inconsistent if you put this here.
I guess we don't really need the pipe update tracepoints for async
flips. We might want to add a separate tracepoint for async flip itself,
or perhaps convey the sync vs. async information via the current
plane update tracepoint.

With this moved to before the tracepoint
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> +
>  	/* We're still in the vblank-evade critical section, this can't race.
>  	 * Would be slightly nice to just grab the vblank count and arm the
>  	 * event outside of the critical section - the spinlock might spin for a
> -- 
> 2.22.0

-- 
Ville Syrjälä
Intel
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