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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 <paul.kocialkowski@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190131132550.26355-1-paul.kocialkowski@bootlin.com
hifive-unleashed-5.1
Paul Kocialkowski 2019-01-31 14:25:50 +01:00 committed by Maxime Ripard
parent 053ff09f1a
commit b14e945bda
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1 changed files with 2 additions and 0 deletions
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drivers/gpu/drm/sun4i/sun4i_tcon.c
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@ -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);
clk_disable_unprepare(tcon->clk);
}