drm/sun4i: tcon: Prepare and enable TCON channel 0 clock at init

paulkocialkowski · mripard · commit b14e945bda8a · 2019-02-01T14:10:51.000+01:00
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
diff --git 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);
 	clk_disable_unprepare(tcon->clk);
 }
 

Original file line number	Diff line number	Diff line change
`@@ -761,6 +761,7 @@ static int sun4i_tcon_init_clocks(struct device *dev,`
`761`	`761`	`return PTR_ERR(tcon->sclk0);`
`762`	`762`	`}`
`763`	`763`	`}`
	`764`	`+ clk_prepare_enable(tcon->sclk0);`
`764`	`765`
`765`	`766`	`if (tcon->quirks->has_channel_1) {`
`766`	`767`	`tcon->sclk1 = devm_clk_get(dev, "tcon-ch1");`
`@@ -775,6 +776,7 @@ static int sun4i_tcon_init_clocks(struct device *dev,`
`775`	`776`
`776`	`777`	`static void sun4i_tcon_free_clocks(struct sun4i_tcon *tcon)`
`777`	`778`	`{`
	`779`	`+ clk_disable_unprepare(tcon->sclk0);`
`778`	`780`	`clk_disable_unprepare(tcon->clk);`
`779`	`781`	`}`
`780`	`782`