linux-kernel - Re: [PATCH v3 04/15] dt-bindings: display: sun4i-drm: Add A83T pipeline

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Message-ID: <20171206215922.vtsa4xqa2e5xz7cp@rob-hp-laptop>
Date:   Wed, 6 Dec 2017 15:59:22 -0600
From:   Rob Herring <robh@...nel.org>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:     Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>, Chen-Yu Tsai <wens@...e.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, plaes@...es.org,
        icenowy@...c.io,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        jernej.skrabec@...l.net, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 04/15] dt-bindings: display: sun4i-drm: Add A83T
 pipeline

On Tue, Dec 05, 2017 at 04:10:16PM +0100, Maxime Ripard wrote:
> The A83T has two video pipelines in parallel that looks quite similar to
> the other SoCs.
> 
> The video planes are handled through a controller called the mixer, and the
> video signal is then passed to the timing controller (TCON).
> 
> And while there is two instances of the mixers and TCONs, they have a
> significant number of differences. The TCONs are quite easy to deal with,
> one is supposed to generate TV (in the broader term, so including things
> like HDMI) signals, the other one LCD (so RGB, LVDS, DSI) signals. And
> while they are called TCON0 and TCON1 in the A83t datasheet, newer SoCs
> call them TCON-TV and TCON-LCD, which seems more appropriate.
> 
> However, the mixers differ mostly by their capabilities, with some features
> being available only in the first one, or the number of planes they expose,
> but also through their register layout. And while the capabilities could be
> represented as properties, the register layout differences would need to
> express all the registers offsets as properties, which is usually quite
> bad. Especially since documentation on that hardware block is close to
> non-existant and we don't even have the list of all those registers in the
> first place.
> 
> So let's call them mixer 0 and 1 in our compatibles, even though the name
> is pretty bad...
> 
> At the moment, we only have tested the code on a board that has a single
> display output, so we're leaving the tcon-tv and mixer1 out.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
> ---
>  Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt | 3 +++
>  1 file changed, 3 insertions(+)

Reviewed-by: Rob Herring <robh@...nel.org>