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, 21 insertions, 0 deletions

diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index 84f95866c02b..f156c930366a 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -20,20 +20,31 @@ static const u32 vkms_formats[] = {
 	DRM_FORMAT_XRGB8888,
 };
 
+struct vkms_crc_data {
+	struct drm_rect src;
+	struct drm_framebuffer fb;
+};
+
 /**
  * vkms_plane_state - Driver specific plane state
  * @base: base plane state
+ * @crc_data: data required for CRC computation
  */
 struct vkms_plane_state {
 	struct drm_plane_state base;
+	struct vkms_crc_data *crc_data;
 };
 
 /**
  * vkms_crtc_state - Driver specific CRTC state
  * @base: base CRTC state
+ * @crc_work: work struct to compute and add CRC entries
+ * @n_frame: frame number for computed CRC
  */
 struct vkms_crtc_state {
 	struct drm_crtc_state base;
+	struct work_struct crc_work;
+	unsigned int n_frame;
 };
 
 struct vkms_output {
@@ -43,6 +54,11 @@ struct vkms_output {
 	struct hrtimer vblank_hrtimer;
 	ktime_t period_ns;
 	struct drm_pending_vblank_event *event;
+	bool crc_enabled;
+	/* ordered wq for crc_work */
+	struct workqueue_struct *crc_workq;
+	/* protects concurrent access to crc_data */
+	spinlock_t lock;
 };
 
 struct vkms_device {
@@ -106,4 +122,9 @@ int vkms_gem_vmap(struct drm_gem_object *obj);
 
 void vkms_gem_vunmap(struct drm_gem_object *obj);
 
+/* CRC Support */
+int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name,
+			size_t *values_cnt);
+void vkms_crc_work_handle(struct work_struct *work);
+
 #endif /* _VKMS_DRV_H_ */