linux-kernel - Re: [PATCH] drm/virtio: fix unblank

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Message-ID: <20200807130956.GE2352366@phenom.ffwll.local>
Date:   Fri, 7 Aug 2020 15:09:56 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     dri-devel@...ts.freedesktop.org, 1882851@...s.launchpad.net,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Chia-I Wu <olvaffe@...il.com>,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@...ts.linux-foundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/virtio: fix unblank

On Fri, Aug 07, 2020 at 12:54:29PM +0200, Gerd Hoffmann wrote:
> When going through a disable/enable cycle without changing the
> framebuffer the optimization added by commit 3954ff10e06e ("drm/virtio:
> skip set_scanout if framebuffer didn't change") causes the screen stay
> blank.  Add a bool to force an update to fix that.
> 
> Cc: 1882851@...s.launchpad.net
> Fixes: 3954ff10e06e ("drm/virtio: skip set_scanout if framebuffer didn't change")
> Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
> ---
>  drivers/gpu/drm/virtio/virtgpu_drv.h     | 1 +
>  drivers/gpu/drm/virtio/virtgpu_display.c | 1 +
>  drivers/gpu/drm/virtio/virtgpu_plane.c   | 4 +++-
>  3 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
> index 9ff9f4ac0522..7b0c319f23c9 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.h
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
> @@ -138,6 +138,7 @@ struct virtio_gpu_output {
>  	int cur_x;
>  	int cur_y;
>  	bool enabled;
> +	bool need_update;
>  };
>  #define drm_crtc_to_virtio_gpu_output(x) \
>  	container_of(x, struct virtio_gpu_output, crtc)
> diff --git a/drivers/gpu/drm/virtio/virtgpu_display.c b/drivers/gpu/drm/virtio/virtgpu_display.c
> index cc7fd957a307..378be5956b30 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_display.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_display.c
> @@ -100,6 +100,7 @@ static void virtio_gpu_crtc_atomic_enable(struct drm_crtc *crtc,
>  	struct virtio_gpu_output *output = drm_crtc_to_virtio_gpu_output(crtc);
>  
>  	output->enabled = true;
> +	output->need_update = true;
>  }
>  
>  static void virtio_gpu_crtc_atomic_disable(struct drm_crtc *crtc,
> diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c b/drivers/gpu/drm/virtio/virtgpu_plane.c
> index 52d24179bcec..5948031a9ce8 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_plane.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
> @@ -163,7 +163,8 @@ static void virtio_gpu_primary_plane_update(struct drm_plane *plane,
>  	    plane->state->src_w != old_state->src_w ||
>  	    plane->state->src_h != old_state->src_h ||
>  	    plane->state->src_x != old_state->src_x ||
> -	    plane->state->src_y != old_state->src_y) {
> +	    plane->state->src_y != old_state->src_y ||
> +	    output->need_update) {

Uh instead of hand-rolling what's essentially a drm_crtc_needs_modeset
check, why not use that one? atomic helpers try to keep the usual suspects
for state transitions already handy, to avoid every driver rolling their
own. Or do I miss something here?
-Daniel


>  		DRM_DEBUG("handle 0x%x, crtc %dx%d+%d+%d, src %dx%d+%d+%d\n",
>  			  bo->hw_res_handle,
>  			  plane->state->crtc_w, plane->state->crtc_h,
> @@ -178,6 +179,7 @@ static void virtio_gpu_primary_plane_update(struct drm_plane *plane,
>  					   plane->state->src_h >> 16,
>  					   plane->state->src_x >> 16,
>  					   plane->state->src_y >> 16);
> +		output->need_update = false;
>  	}
>  
>  	virtio_gpu_cmd_resource_flush(vgdev, bo->hw_res_handle,
> -- 
> 2.18.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch