[PATCH AUTOSEL 5.4 051/108] drm/stm: ltdc: check crtc state before enabling LIE

[Sasha Levin]

From: Yannick Fertre <yannick.fertre@xxxxxx>

[ Upstream commit a6bd58c51ac43083f3977057a7ad668def55812f ]

Following investigations of a hardware bug, the LIE interrupt
can occur while the display controller is not activated.
LIE interrupt (vblank) don't have to be set if the CRTC is not
enabled.

Signed-off-by: Yannick Fertre <yannick.fertre@xxxxxx>
Acked-by: Philippe Cornu <philippe.cornu@xxxxxx>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/1579601650-7055-1-git-send-email-yannick.fertre@xxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/gpu/drm/stm/ltdc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 3ab4fbf8eb0d1..2526dfb77401c 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -653,9 +653,14 @@ static const struct drm_crtc_helper_funcs ltdc_crtc_helper_funcs = {
 static int ltdc_crtc_enable_vblank(struct drm_crtc *crtc)
 {
 	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
+	struct drm_crtc_state *state = crtc->state;
 
 	DRM_DEBUG_DRIVER("\n");
-	reg_set(ldev->regs, LTDC_IER, IER_LIE);
+
+	if (state->enable)
+		reg_set(ldev->regs, LTDC_IER, IER_LIE);
+	else
+		return -EPERM;
 
 	return 0;
 }
-- 
2.20.1