[PATCH AUTOSEL 4.19 36/66] drm/stm: ltdc: check crtc state before enabling LIE

[Sasha Levin]

From: Yannick Fertre <yannick.fertre at st.com>

[ 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 at st.com>
Acked-by: Philippe Cornu <philippe.cornu at st.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard at st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1579601650-7055-1-git-send-email-yannick.fertre@st.com
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 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 477d0a27b9a5d..75d108db127c8 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -612,9 +612,14 @@ 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