[PATCH 5.4 132/270] drm/stm: repair runtime power management

[Greg Kroah-Hartman]

From: Marek Vasut <marex at denx.de>

[ Upstream commit ebd267b2e3c25d5f93a08528b47c036569eb8744 ]

Add missing pm_runtime_get_sync() into ltdc_crtc_atomic_enable() to
match pm_runtime_put_sync() in ltdc_crtc_atomic_disable(), otherwise
the LTDC might suspend via runtime PM, disable clock, and then fail
to resume later on.

The test which triggers it is roughly -- run qt5 application which
uses eglfs platform and etnaviv, stop the application, sleep for 15
minutes, run the application again. This leads to a timeout waiting
for vsync, because the LTDC has suspended, but did not resume.

Fixes: 35ab6cfbf211 ("drm/stm: support runtime power management")
Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Yannick Fertré <yannick.fertre at st.com>
Cc: Philippe Cornu <philippe.cornu at st.com>
Cc: Benjamin Gaignard <benjamin.gaignard at linaro.org>
Cc: Vincent Abriou <vincent.abriou at st.com>
Cc: Maxime Coquelin <mcoquelin.stm32 at gmail.com>
Cc: Alexandre Torgue <alexandre.torgue at st.com>
To: dri-devel at lists.freedesktop.org
Cc: linux-stm32 at st-md-mailman.stormreply.com
Cc: linux-arm-kernel at lists.infradead.org
Acked-by: Philippe Cornu <philippe.cornu at st.com>
Tested-by: Yannick Fertre <yannick.fertre at st.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard at st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200229221649.90813-1-marex@denx.de
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 drivers/gpu/drm/stm/ltdc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 3ab4fbf8eb0d1..51571f7246abf 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -424,9 +424,12 @@ static void ltdc_crtc_atomic_enable(struct drm_crtc *crtc,
 				    struct drm_crtc_state *old_state)
 {
 	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
+	struct drm_device *ddev = crtc->dev;
 
 	DRM_DEBUG_DRIVER("\n");
 
+	pm_runtime_get_sync(ddev->dev);
+
 	/* Sets the background color value */
 	reg_write(ldev->regs, LTDC_BCCR, BCCR_BCBLACK);
 
-- 
2.25.1