* [PATCH] drm/sun4i: tcon: Prepare and enable TCON channel 0 clock at init
@ 2019-01-31 13:25 Paul Kocialkowski
2019-02-01 13:12 ` Maxime Ripard
0 siblings, 1 reply; 2+ messages in thread
From: Paul Kocialkowski @ 2019-01-31 13:25 UTC (permalink / raw)
To: dri-devel, linux-arm-kernel, linux-kernel, linux-sunxi
Cc: Maxime Ripard, David Airlie, Chen-Yu Tsai, Maxime Ripard,
Paul Kocialkowski
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>
---
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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] drm/sun4i: tcon: Prepare and enable TCON channel 0 clock at init
2019-01-31 13:25 [PATCH] drm/sun4i: tcon: Prepare and enable TCON channel 0 clock at init Paul Kocialkowski
@ 2019-02-01 13:12 ` Maxime Ripard
0 siblings, 0 replies; 2+ messages in thread
From: Maxime Ripard @ 2019-02-01 13:12 UTC (permalink / raw)
To: Paul Kocialkowski
Cc: dri-devel, linux-arm-kernel, linux-kernel, linux-sunxi,
David Airlie, Chen-Yu Tsai
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On Thu, Jan 31, 2019 at 02:25:50PM +0100, Paul Kocialkowski wrote:
> 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>
Applied, thanks!
Maxime
--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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