linux-kernel - Re: [PATCH] drm/sun4i: Workaround TCON TOP conflict between DE0 and DE1

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Message-ID: <Zy4c9BFcrz2JVU6k@titan>
Date: Sat, 9 Nov 2024 01:15:16 +1100
From: John Watts <contact@...kia.org>
To: Parthiban <parthiban@...umiz.com>
Cc: Andre Przywara <andre.przywara@....com>,
	Maxime Ripard <mripard@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Samuel Holland <samuel@...lland.org>,
	dri-devel@...ts.freedesktop.org,
	linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/sun4i: Workaround TCON TOP conflict between DE0 and
 DE1

On Fri, Nov 08, 2024 at 07:36:16PM +0530, Parthiban wrote:
> To add, 0x20 will be DE0 <--> LCD0 and DE1 <--> TV0. Below note (copied from
> R40) states the priority of the DE selection, which fails to work? Not sure,
> may be disabling CORE1_SCLK_GATE and CORE1_HCLK_GATE in de2-clk helps.
> 
> With A133 following the same as T113 with single mixer without TV, still
> sets 0x20 in vendor kernel.
> 
> copied from R40:
> Note: The priority of DE0 is higher than DE1.
> If TCON_LCD0 selects DE0 and DE1 as source at the same time, then
> DE0 will be used for the source of TCON_LCD0.

Hi there,

Yes that was a pretty bad typo, I meant to say DE1 to TV0
The prioritization seems broken in the T113 at least, it's racy from
what I see in testing. I should note this in the patch too.

I looked at the datasheets and kernel code briefly: I can't seem to
figure out what SCLK/HCLK gating does and I don't think the kernel
touches these registers which are gated by default.

> Thanks,
> Parthiban

John Watts