drm/vkms: Implement CRC debugfs API

This patch implement the necessary functions to compute and add CRCs
entries:

- Implement the set_crc_source() callback.
- Compute CRC using crc32 on the visible part of the framebuffer.
- Use ordered workqueue per output to compute and add CRC at the end
  of a vblank.
- Use appropriate synchronization methods since the CRC computation must
  be atomic wrt the generated vblank event for a given atomic update, by
  using spinlock across atomic_begin/atomic_flush to wrap the event
  handling code completely and match the flip event with the CRC.

Since vkms_crc_work_handle() can sleep, spinlock can't be acquired
while accessing vkms_output->primary_crc to compute CRC.
To make sure the data is updated and released without conflict with
the vkms_crc_work_handle(), the work_struct is flushed @crtc_destroy
and the data is updated before scheduling the work handle again, as
follow:

* CRC data update:
1- store vkms_crc_data {fb, src} per plane_state
2- @plane_duplicate_state -> allocate vkms_crc_data
3- during atomic commit (@atomic_update) ->
	a) copy {fb, src} to plane_state->crc_data
	b) get reference to fb,
3- @plane_destroy_state -> a) if (fb refcount) remove reference to fb
			   b) deallocate crc_data

* Atomic Commit:
1- vkms_plane_atomic_check
2- vkms_prepare_fb -> vmap vkms_gem_obj->vaddr
3- atomic_begin -> hold crc spinlock
4- atomic_plane_update -> a) update vkms_output->primary_crc
			  b) get reference to fb
5- atomic_flush -> a) send vblank event while holding event_lock
		   b) release crc spinlock

* hrtimer regular callback:
1- hold crc spinlock
2- drm_crtc_handle_vblank()
3- queue vkms_crc_work_handle
4- release crc spinlock

* cleanup:
1- @cleanup_fb ->vunmap vkms_gem_obj->vaddr
2- @crtc_destroy -> flush work struct
3- @plane_destroy -> a) if (fb refcount) remove reference to fb
		     b) deallocate crc_data

Signed-off-by: Haneen Mohammed <hamohammed.sa@gmail.com>
[seanpaul fixed typo in vkms_crtc s/vblamk/vblank/]
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/b948327f48c3e70ab232b4a0848ee6d033b26484.1533171495.git.hamohammed.sa@gmail.com

1 files changed, 30 insertions, 0 deletions

diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
index 70fca22bc51b..c91661631c76 100644
--- a/drivers/gpu/drm/vkms/vkms_plane.c
+++ b/drivers/gpu/drm/vkms/vkms_plane.c
@@ -16,11 +16,18 @@ static struct drm_plane_state *
 vkms_plane_duplicate_state(struct drm_plane *plane)
 {
 	struct vkms_plane_state *vkms_state;
+	struct vkms_crc_data *crc_data;
 
 	vkms_state = kzalloc(sizeof(*vkms_state), GFP_KERNEL);
 	if (!vkms_state)
 		return NULL;
 
+	crc_data = kzalloc(sizeof(*crc_data), GFP_KERNEL);
+	if (WARN_ON(!crc_data))
+		DRM_INFO("Couldn't allocate crc_data");
+
+	vkms_state->crc_data = crc_data;
+
 	__drm_atomic_helper_plane_duplicate_state(plane,
 						  &vkms_state->base);
 
@@ -31,6 +38,18 @@ static void vkms_plane_destroy_state(struct drm_plane *plane,
 				     struct drm_plane_state *old_state)
 {
 	struct vkms_plane_state *vkms_state = to_vkms_plane_state(old_state);
+	struct drm_crtc *crtc = vkms_state->base.crtc;
+
+	if (crtc) {
+		/* dropping the reference we acquired in
+		 * vkms_primary_plane_update()
+		 */
+		if (drm_framebuffer_read_refcount(&vkms_state->crc_data->fb))
+			drm_framebuffer_put(&vkms_state->crc_data->fb);
+	}
+
+	kfree(vkms_state->crc_data);
+	vkms_state->crc_data = NULL;
 
 	__drm_atomic_helper_plane_destroy_state(old_state);
 	kfree(vkms_state);
@@ -65,6 +84,17 @@ static const struct drm_plane_funcs vkms_plane_funcs = {
 static void vkms_primary_plane_update(struct drm_plane *plane,
 				      struct drm_plane_state *old_state)
 {
+	struct vkms_plane_state *vkms_plane_state;
+	struct vkms_crc_data *crc_data;
+
+	if (!plane->state->crtc || !plane->state->fb)
+		return;
+
+	vkms_plane_state = to_vkms_plane_state(plane->state);
+	crc_data = vkms_plane_state->crc_data;
+	memcpy(&crc_data->src, &plane->state->src, sizeof(struct drm_rect));
+	memcpy(&crc_data->fb, plane->state->fb, sizeof(struct drm_framebuffer));
+	drm_framebuffer_get(&crc_data->fb);
 }
 
 static int vkms_plane_atomic_check(struct drm_plane *plane,