[PATCH v4 4/4] drm/hypervdrm: Use vblank timer

[Thomas Zimmermann <tzimmermann@suse.de>]

HyperV's virtual hardware does not provide vblank interrupts. Use a
vblank timer to simulate the interrupt. Rate-limits the display's
update frequency to the display-mode settings. Avoids excessive CPU
overhead with compositors that do not rate-limit their output.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/gpu/drm/hyperv/hyperv_drm_modeset.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c b/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
index 945b9482bcb3..6e6eb1c12a68 100644
--- a/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
+++ b/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
@@ -19,6 +19,8 @@
 #include <drm/drm_probe_helper.h>
 #include <drm/drm_panic.h>
 #include <drm/drm_plane.h>
+#include <drm/drm_vblank.h>
+#include <drm/drm_vblank_helper.h>
 
 #include "hyperv_drm.h"
 
@@ -111,11 +113,15 @@ static void hyperv_crtc_helper_atomic_enable(struct drm_crtc *crtc,
 				crtc_state->mode.hdisplay,
 				crtc_state->mode.vdisplay,
 				plane_state->fb->pitches[0]);
+
+	drm_crtc_vblank_on(crtc);
 }
 
 static const struct drm_crtc_helper_funcs hyperv_crtc_helper_funcs = {
 	.atomic_check = drm_crtc_helper_atomic_check,
+	.atomic_flush = drm_crtc_vblank_atomic_flush,
 	.atomic_enable = hyperv_crtc_helper_atomic_enable,
+	.atomic_disable = drm_crtc_vblank_atomic_disable,
 };
 
 static const struct drm_crtc_funcs hyperv_crtc_funcs = {
@@ -125,6 +131,7 @@ static const struct drm_crtc_funcs hyperv_crtc_funcs = {
 	.page_flip = drm_atomic_helper_page_flip,
 	.atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
 	.atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
+	DRM_CRTC_VBLANK_TIMER_FUNCS,
 };
 
 static int hyperv_plane_atomic_check(struct drm_plane *plane,
@@ -321,6 +328,10 @@ int hyperv_mode_config_init(struct hyperv_drm_device *hv)
 		return ret;
 	}
 
+	ret = drm_vblank_init(dev, 1);
+	if (ret)
+		return ret;
+
 	drm_mode_config_reset(dev);
 
 	return 0;
-- 
2.51.0