1 files changed, 45 insertions, 0 deletions
diff --git a/target/linux/brcm2708/patches-4.19/950-0591-drm-vc4-Fix-vblank-timestamping-for-firmwarekms.patch b/target/linux/brcm2708/patches-4.19/950-0591-drm-vc4-Fix-vblank-timestamping-for-firmwarekms.patch
new file mode 100644
index 0000000000..979dfc7b8a
--- /dev/null
+++ b/target/linux/brcm2708/patches-4.19/950-0591-drm-vc4-Fix-vblank-timestamping-for-firmwarekms.patch
@@ -0,0 +1,45 @@
+From 2372381c6850bf862a43997d95f4a5abcde156e9 Mon Sep 17 00:00:00 2001
+From: Eric Anholt <eric@anholt.net>
+Date: Tue, 2 Apr 2019 13:29:00 -0700
+Subject: [PATCH 591/773] drm/vc4: Fix vblank timestamping for firmwarekms.
+
+The core doesn't expect a false return from the scanoutpos function in
+normal usage, so we were doing the precise vblank timestamping path
+and thus "immediate" vblank disables (even though firmwarekms can't
+actually disable vblanks interrupts, sigh), and the kernel would get
+confused when getting timestamp info when also turning vblanks back
+on.
+
+Signed-off-by: Eric Anholt <eric@anholt.net>
+---
+ drivers/gpu/drm/vc4/vc4_crtc.c         | 3 ---
+ drivers/gpu/drm/vc4/vc4_firmware_kms.c | 6 ++++++
+ 2 files changed, 6 insertions(+), 3 deletions(-)
+
+--- a/drivers/gpu/drm/vc4/vc4_crtc.c
++++ b/drivers/gpu/drm/vc4/vc4_crtc.c
+@@ -133,9 +133,6 @@ bool vc4_crtc_get_scanoutpos(struct drm_
+ 	int vblank_lines;
+ 	bool ret = false;
+ 
+-	if (vc4->firmware_kms)
+-		return 0;
+-
+ 	/* preempt_disable_rt() should go right here in PREEMPT_RT patchset. */
+ 
+ 	/* Get optional system timestamp before query. */
+--- a/drivers/gpu/drm/vc4/vc4_firmware_kms.c
++++ b/drivers/gpu/drm/vc4/vc4_firmware_kms.c
+@@ -673,6 +673,12 @@ static int vc4_fkms_bind(struct device *
+ 
+ 	vc4->firmware_kms = true;
+ 
++	/* firmware kms doesn't have precise a scanoutpos implementation, so
++	 * we can't do the precise vblank timestamp mode.
++	 */
++	drm->driver->get_scanout_position = NULL;
++	drm->driver->get_vblank_timestamp = NULL;
++
+ 	vc4_crtc = devm_kzalloc(dev, sizeof(*vc4_crtc), GFP_KERNEL);
+ 	if (!vc4_crtc)
+ 		return -ENOMEM;