[PATCH] drm/stm: Enable RPM during fbdev registration

[Marek Vasut]

Enable runtime PM before registering the fbdev emulation and disable it
afterward, otherwise register access to the LTDC IP during the fbdev
emulation registration might hang the system.

The problem happens because RPM is activated at the end of ltdc_load(),
but the fbdev emulation registration happens only after that, and ends
up calling ltdc_crtc_mode_set_nofb(), which checks whether RPM is active
and only if it is not active, calls pm_runtime_get_sync() to enable the
clock and so on. If the clock are not enabled, any register access in
ltdc_crtc_mode_set_nofb() could hang the platform completely.

This patch makes sure that ltdc_crtc_mode_set_nofb() is called within
pm_runtime_get_sync(), so with clock enabled.

Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Alexandre Torgue <alexandre.torgue at st.com>
Cc: Benjamin Gaignard <benjamin.gaignard at st.com>
Cc: Philippe Cornu <philippe.cornu at st.com>
Cc: Yannick Fertré <yannick.fertre at st.com>
Cc: dri-devel at lists.freedesktop.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-stm32 at st-md-mailman.stormreply.com
---
 drivers/gpu/drm/stm/drv.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/stm/drv.c b/drivers/gpu/drm/stm/drv.c
index 411103f013e2..d8921edc83db 100644
--- a/drivers/gpu/drm/stm/drv.c
+++ b/drivers/gpu/drm/stm/drv.c
@@ -197,7 +197,9 @@ static int stm_drm_platform_probe(struct platform_device *pdev)
 	if (ret)
 		goto err_put;
 
+	pm_runtime_get_sync(ddev->dev);
 	drm_fbdev_generic_setup(ddev, 16);
+	pm_runtime_put_sync(ddev->dev);
 
 	return 0;
 
-- 
2.28.0