Re: [RFC PATCH 3/3] drm/vkms: add overlay support

[Melissa Wen <melissa.srw@gmail.com>]

On 02/22, Daniel Vetter wrote:
> On Sat, Feb 20, 2021 at 11:42:12AM -0300, Melissa Wen wrote:
> > Add support to overlay plane, in addition to primary and cursor
> > planes. In this approach, the plane composition still requires an
> > active primary plane and planes are composed associatively in the
> > order: (primary <- overlay) <- cursor
> > 
> > It enables to run the following IGT tests successfully:
> > - kms_plane_cursor:
> >   - pipe-A-[overlay, primary, viewport]-size-[64, 128, 256]
> > - kms_atomic:
> >   - plane-overlay-legacy
> > and preserves the successful execution of kms_cursor_crc,
> > kms_writeback and kms_flip
> > 
> > Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
> > ---
> >  drivers/gpu/drm/vkms/vkms_composer.c | 27 +++++++++++++++++----------
> >  drivers/gpu/drm/vkms/vkms_drv.c      |  5 +++++
> >  drivers/gpu/drm/vkms/vkms_drv.h      |  1 +
> >  drivers/gpu/drm/vkms/vkms_output.c   | 17 +++++++++++++++--
> >  drivers/gpu/drm/vkms/vkms_plane.c    | 20 +++++++++++++++-----
> >  5 files changed, 53 insertions(+), 17 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> > index be8f1d33c645..2116da9b5a43 100644
> > --- a/drivers/gpu/drm/vkms/vkms_composer.c
> > +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> > @@ -144,11 +144,12 @@ static void compose_planes(struct vkms_composer *primary_composer,
> >  
> >  static int composite(void **vaddr_out,
> >  		     struct vkms_composer *primary_composer,
> > -		     struct vkms_composer *cursor_composer)
> > +		     struct vkms_crtc_state *crtc_state)
> >  {
> >  	struct drm_framebuffer *fb = &primary_composer->fb;
> >  	struct drm_gem_object *gem_obj = drm_gem_fb_get_obj(fb, 0);
> >  	struct drm_gem_shmem_object *shmem_obj = to_drm_gem_shmem_obj(gem_obj);
> > +	int i;
> >  
> >  	if (!*vaddr_out) {
> >  		*vaddr_out = kzalloc(shmem_obj->base.size, GFP_KERNEL);
> > @@ -163,8 +164,14 @@ static int composite(void **vaddr_out,
> >  
> >  	memcpy(*vaddr_out, shmem_obj->vaddr, shmem_obj->base.size);
> >  
> > -	if (cursor_composer)
> > -		compose_planes(primary_composer, cursor_composer, *vaddr_out);
> > +	/* If there are other planes besides primary, we consider the active
> > +	 * planes should be in z-order and compose them associatively:
> > +	 * ((primary <- overlay) <- cursor)
> > +	 */
> > +	for (i = 1; i < crtc_state->num_active_planes; i++)
> > +		compose_planes(primary_composer,
> > +			       crtc_state->active_planes[i]->composer,
> > +			       *vaddr_out);
> >  
> >  	return 0;
> >  }
> > @@ -186,7 +193,7 @@ void vkms_composer_worker(struct work_struct *work)
> >  	struct drm_crtc *crtc = crtc_state->base.crtc;
> >  	struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
> >  	struct vkms_composer *primary_composer = NULL;
> > -	struct vkms_composer *cursor_composer = NULL;
> > +	struct vkms_plane_state *act_plane = NULL;
> >  	bool crc_pending, wb_pending;
> >  	void *vaddr_out = NULL;
> >  	u32 crc32 = 0;
> > @@ -210,11 +217,11 @@ void vkms_composer_worker(struct work_struct *work)
> >  	if (!crc_pending)
> >  		return;
> >  
> > -	if (crtc_state->num_active_planes >= 1)
> > -		primary_composer = crtc_state->active_planes[0]->composer;
> > -
> > -	if (crtc_state->num_active_planes == 2)
> > -		cursor_composer = crtc_state->active_planes[1]->composer;
> > +	if (crtc_state->num_active_planes >= 1) {
> > +		act_plane = crtc_state->active_planes[0];
> > +		if (act_plane->base.plane->type == DRM_PLANE_TYPE_PRIMARY)
> > +			primary_composer = act_plane->composer;
> > +	}
> >  
> >  	if (!primary_composer)
> >  		return;
> > @@ -222,7 +229,7 @@ void vkms_composer_worker(struct work_struct *work)
> >  	if (wb_pending)
> >  		vaddr_out = crtc_state->active_writeback;
> >  
> > -	ret = composite(&vaddr_out, primary_composer, cursor_composer);
> > +	ret = composite(&vaddr_out, primary_composer, crtc_state);
> >  	if (ret) {
> >  		if (ret == -EINVAL && !wb_pending)
> >  			kfree(vaddr_out);
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> > index 2173b82606f6..027ffe759440 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.c
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> > @@ -44,6 +44,10 @@ static bool enable_writeback = true;
> >  module_param_named(enable_writeback, enable_writeback, bool, 0444);
> >  MODULE_PARM_DESC(enable_writeback, "Enable/Disable writeback connector support");
> >  
> > +static bool enable_overlay;
> > +module_param_named(enable_overlay, enable_overlay, bool, 0444);
> > +MODULE_PARM_DESC(enable_overlay, "Enable/Disable overlay support");
> > +
> >  DEFINE_DRM_GEM_FOPS(vkms_driver_fops);
> >  
> >  static void vkms_release(struct drm_device *dev)
> > @@ -198,6 +202,7 @@ static int __init vkms_init(void)
> >  
> >  	config->cursor = enable_cursor;
> >  	config->writeback = enable_writeback;
> > +	config->overlay = enable_overlay;
> >  
> >  	return vkms_create(config);
> >  }
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> > index 9ad5ad8b7737..784219da8df0 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.h
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> > @@ -85,6 +85,7 @@ struct vkms_device;
> >  struct vkms_config {
> >  	bool writeback;
> >  	bool cursor;
> > +	bool overlay;
> >  	/* only set when instantiated */
> >  	struct vkms_device *dev;
> >  };
> > diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
> > index 05d3bb45e6c1..c60d0f2e7a37 100644
> > --- a/drivers/gpu/drm/vkms/vkms_output.c
> > +++ b/drivers/gpu/drm/vkms/vkms_output.c
> > @@ -39,7 +39,7 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> >  	struct drm_connector *connector = &output->connector;
> >  	struct drm_encoder *encoder = &output->encoder;
> >  	struct drm_crtc *crtc = &output->crtc;
> > -	struct drm_plane *primary, *cursor = NULL;
> > +	struct drm_plane *primary, *cursor = NULL, *overlay = NULL;
> >  	int ret;
> >  	int writeback;
> >  
> > @@ -51,6 +51,16 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> >  	if (ret)
> >  		goto err_crtc;
> >  
> > +	if (vkmsdev->config->overlay) {
> > +		overlay = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_OVERLAY, index);
> > +		if (IS_ERR(overlay)) {
> > +			ret = PTR_ERR(overlay);
> > +			goto err_overlay;
> > +		}
> > +		if (overlay && !overlay->possible_crtcs)
> > +			overlay->possible_crtcs = drm_crtc_mask(crtc);
> > +	}
> > +
> >  	if (vkmsdev->config->cursor) {
> >  		cursor = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_CURSOR, index);
> >  		if (IS_ERR(cursor)) {
> > @@ -58,7 +68,6 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> >  			goto err_cursor;
> >  		}
> >  	}
> > -
> >  	crtc->cursor = cursor;
> >  	if (cursor && !cursor->possible_crtcs)
> >  		cursor->possible_crtcs = drm_crtc_mask(crtc);
> > @@ -108,6 +117,10 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> >  	if (vkmsdev->config->cursor)
> >  		drm_plane_cleanup(cursor);
> >  
> > +err_overlay:
> > +	if (vkmsdev->config->overlay)
> > +		drm_plane_cleanup(overlay);
> 
> Using drmm_universal_plane_init would be nice so we can ditch a bunch of
> this cleanup code, but can be done later. Same for crtc.

Hmm.. I'll check it. Just to be sure, would it be drmm_universal_plane_alloc?
> 
> > +
> >  err_crtc:
> >  	drm_plane_cleanup(primary);
> >  
> > diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> > index 0824327cc860..8e7bb84bc894 100644
> > --- a/drivers/gpu/drm/vkms/vkms_plane.c
> > +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> > @@ -19,6 +19,11 @@ static const u32 vkms_cursor_formats[] = {
> >  	DRM_FORMAT_ARGB8888,
> >  };
> >  
> > +static const u32 vkms_overlay_formats[] = {
> > +	DRM_FORMAT_ARGB8888,
> > +	DRM_FORMAT_XRGB8888,
> 
> Does the blend function correctly work for XRGB, i.e. ignore the alpha
> channel? Maybe even split that functionality out into a separate patch
> (and then also add it for the cursor plane, so we keep one unified format
> list for non-primary planes) so it sticks out more.
> 
Initially, I was also reusing the cursor formart, because ARGB makes
more sense to me. But I checked that IGT considers a XRGB overlay, that
is why I included both. I verified in tests using XRGB that the color is
received as a full-opaque RGB: [FF-RR-GG-BB] and the alpha_blending
function composes these two types correctly. If this is the regular
behavior for XRGB, I think I can unify cursor and overlay formats in the
previous patch that generalize some cursor variables for reusing.

> 
> > +};
> > +
> >  static struct drm_plane_state *
> >  vkms_plane_duplicate_state(struct drm_plane *plane)
> >  {
> > @@ -127,7 +132,7 @@ static int vkms_plane_atomic_check(struct drm_plane *plane,
> >  	if (IS_ERR(crtc_state))
> >  		return PTR_ERR(crtc_state);
> >  
> > -	if (plane->type == DRM_PLANE_TYPE_CURSOR)
> > +	if (plane->type != DRM_PLANE_TYPE_PRIMARY)
> >  		can_position = true;
> >  
> >  	ret = drm_atomic_helper_check_plane_state(state, crtc_state,
> > @@ -195,14 +200,19 @@ struct drm_plane *vkms_plane_init(struct vkms_device *vkmsdev,
> >  	int ret, nformats;
> >  
> >  	plane = kzalloc(sizeof(*plane), GFP_KERNEL);
> > -	if (!plane)
> > -		return ERR_PTR(-ENOMEM);
> >  
> > -	if (type == DRM_PLANE_TYPE_CURSOR) {
> > +	switch (type) {
> > +	case DRM_PLANE_TYPE_CURSOR:
> >  		formats = vkms_cursor_formats;
> >  		nformats = ARRAY_SIZE(vkms_cursor_formats);
> >  		funcs = &vkms_primary_helper_funcs;
> > -	} else {
> > +		break;
> > +	case DRM_PLANE_TYPE_OVERLAY:
> > +		formats = vkms_overlay_formats;
> > +		nformats = ARRAY_SIZE(vkms_overlay_formats);
> > +		funcs = &vkms_primary_helper_funcs;
> > +		break;
> > +	default:
> >  		formats = vkms_formats;
> >  		nformats = ARRAY_SIZE(vkms_formats);
> >  		funcs = &vkms_primary_helper_funcs;
> 
> Tbf my brain is somewhat toast today, but aside from the few questions I
> think this looks like a solid approach.

Thanks for review. I'll address the improvements you pointed out here
and send a new version.

Melissa

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