diff options
authorPaul Kocialkowski <>2019-01-31 14:25:50 +0100
committerMaxime Ripard <>2019-02-01 14:10:51 +0100
commitb14e945bda8ae227d1bf2b1837c0c4a61721cd1a (patch)
parent053ff09f1a8f2151339f9fda457c5250929d1c49 (diff)
drm/sun4i: tcon: Prepare and enable TCON channel 0 clock at init
When initializing clocks, a reference to the TCON channel 0 clock is obtained. However, the clock is never prepared and enabled later. Switching from simplefb to DRM actually disables the clock (that was usually configured by U-Boot) because of that. On the V3s, this results in a hang when writing to some mixer registers when switching over to DRM from simplefb. Fix this by preparing and enabling the clock when initializing other clocks. Waiting for sun4i_tcon_channel_enable to enable the clock is apparently too late and results in the same mixer register access hang. Signed-off-by: Paul Kocialkowski <> Signed-off-by: Maxime Ripard <> Link:
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index 0420f5c978b9..cf45d0f940f9 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -761,6 +761,7 @@ static int sun4i_tcon_init_clocks(struct device *dev,
return PTR_ERR(tcon->sclk0);
+ clk_prepare_enable(tcon->sclk0);
if (tcon->quirks->has_channel_1) {
tcon->sclk1 = devm_clk_get(dev, "tcon-ch1");
@@ -775,6 +776,7 @@ static int sun4i_tcon_init_clocks(struct device *dev,
static void sun4i_tcon_free_clocks(struct sun4i_tcon *tcon)
+ clk_disable_unprepare(tcon->sclk0);