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 <paul.kocialkowski@xxxxxxxxxxx>
---
drivers/gpu/drm/sun4i/sun4i_tcon.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index e987615c16f1..b31f5d95cadb 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -371,6 +371,7 @@ static int sun4i_tcon_init_clocks(struct device *dev,
dev_err(dev, "Couldn't get the TCON channel 0 clock\n");
return PTR_ERR(tcon->sclk0);
}
+ clk_prepare_enable(tcon->sclk0);
if (tcon->quirks->has_channel_1) {
tcon->sclk1 = devm_clk_get(dev, "tcon-ch1");
@@ -385,6 +386,7 @@ static int sun4i_tcon_init_clocks(struct device *dev,
static void sun4i_tcon_free_clocks(struct sun4i_tcon *tcon)
{
+ clk_disable_unprepare(tcon->sclk0);
clk_disable_unprepare(tcon->clk);
}
--
2.20.1
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