linux-kernel - Re: [PATCH] drm/sun4i: tcon: Prepare and enable TCON channel 0 clock at init

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Message-ID: <20190201131218.633gv3npsekliezj@flea>
Date:   Fri, 1 Feb 2019 14:12:18 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com, David Airlie <airlied@...ux.ie>,
        Chen-Yu Tsai <wens@...e.org>
Subject: Re: [PATCH] drm/sun4i: tcon: Prepare and enable TCON channel 0 clock
 at init

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@...tlin.com>

Applied, thanks!
Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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