Re: [PATCH 1/2] drm/i915: Unset legacy_cursor_update early in intel_atomic_commit, v3.

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Sep 19, 2017 at 02:14:18PM +0200, Maarten Lankhorst wrote:
> Commit b44d5c0c105a ("drm/i915: Always wait for flip_done, v2.") removed
> the call to wait_for_vblanks and replaced it with flip_done.
> 
> Unfortunately legacy_cursor_update was unset too late, and the
> replacement call drm_atomic_helper_wait_for_flip_done() was
> a noop. Make sure that its unset before setup_commit() is
> called to fix this issue.
> 
> Changes since v1:
> - Force vblank wait for watermarks not yet converted to atomic too. (Ville)
> - Use for_each_new_intel_crtc_in_state. (Ville)
> Changes since v2:
> - Move the optimization to a separate commit. (Ville)
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Fixes: b44d5c0c105a ("drm/i915: Always wait for flip_done, v2.")
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102675
> Testcase: kms_cursor_crc
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Reported-by: Marta Löfstedt <marta.lofstedt@intel.com>
> Cc: Marta Löfstedt <marta.lofstedt@intel.com>
> Tested-by: Marta Löfstedt <marta.lofstedt@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 33 ++++++++++++++++-----------------
>  1 file changed, 16 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 8599e425abb1..a85ca19a0c45 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -12517,21 +12517,10 @@ static int intel_atomic_commit(struct drm_device *dev,
>  	struct drm_i915_private *dev_priv = to_i915(dev);
>  	int ret = 0;
>  
> -	ret = drm_atomic_helper_setup_commit(state, nonblock);
> -	if (ret)
> -		return ret;
> -
>  	drm_atomic_state_get(state);
>  	i915_sw_fence_init(&intel_state->commit_ready,
>  			   intel_atomic_commit_ready);
>  
> -	ret = intel_atomic_prepare_commit(dev, state);
> -	if (ret) {
> -		DRM_DEBUG_ATOMIC("Preparing state failed with %i\n", ret);
> -		i915_sw_fence_commit(&intel_state->commit_ready);
> -		return ret;
> -	}
> -
>  	/*
>  	 * The intel_legacy_cursor_update() fast path takes care
>  	 * of avoiding the vblank waits for simple cursor
> @@ -12540,11 +12529,11 @@ static int intel_atomic_commit(struct drm_device *dev,
>  	 * updates happen during the correct frames. Gen9+ have
>  	 * double buffered watermarks and so shouldn't need this.
>  	 *
> -	 * Do this after drm_atomic_helper_setup_commit() and
> -	 * intel_atomic_prepare_commit() because we still want
> -	 * to skip the flip and fb cleanup waits. Although that
> -	 * does risk yanking the mapping from under the display
> -	 * engine.
> +	 * Unset state->legacy_cursor_update before the call to
> +	 * drm_atomic_helper_setup_commit() because otherwise
> +	 * drm_atomic_helper_wait_for_flip_done() is a noop and
> +	 * we get FIFO underruns because we didn't wait
> +	 * for vblank.
>  	 *
>  	 * FIXME doing watermarks and fb cleanup from a vblank worker
>  	 * (assuming we had any) would solve these problems.
> @@ -12552,7 +12541,17 @@ static int intel_atomic_commit(struct drm_device *dev,
>  	if (INTEL_GEN(dev_priv) < 9)
>  		state->legacy_cursor_update = false;
>  
> -	ret = drm_atomic_helper_swap_state(state, true);
> +	ret = intel_atomic_prepare_commit(dev, state);
> +	if (ret) {
> +		DRM_DEBUG_ATOMIC("Preparing state failed with %i\n", ret);
> +		i915_sw_fence_commit(&intel_state->commit_ready);
> +		return ret;
> +	}
> +
> +	ret = drm_atomic_helper_setup_commit(state, nonblock);

Hmm. One thing I noticed here. Previously if this failed we just called
i915_sw_fence_commit(). Now we will also call
drm_atomic_helper_cleanup_planes(). Is that going to be a problem?

> +	if (!ret)
> +		ret = drm_atomic_helper_swap_state(state, true);
> +
>  	if (ret) {
>  		i915_sw_fence_commit(&intel_state->commit_ready);
>  
> -- 
> 2.14.1

-- 
Ville Syrjälä
Intel OTC
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