linux-kernel - Re: [PATCH 0/2] drm/panel: Add support for the Sitronix ST7789V

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Message-ID: <20170206103938.3yghvugiwpzkij6r@lukather>
Date:   Mon, 6 Feb 2017 11:39:38 +0100
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Noralf Trønnes <noralf@...nnes.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 0/2] drm/panel: Add support for the Sitronix ST7789V

Hi Noralf,

On Fri, Feb 03, 2017 at 07:48:51PM +0100, Noralf Trønnes wrote:
> 
> Den 03.02.2017 10.59, skrev Maxime Ripard:
> > Hi,
> > 
> > Here is an attempt at supporting the ST7789V LCD controller from Sitronix.
> 
> What happens if there's another panel driven by ST7789V that needs
> a different controller initialization?

You know those panels / controllers much better than I do, but why
would that be the case?

> Maybe it's better to name it after the panel, not the controller.

I guess you could also use that panel directly without the controller?

> > It is controlled through an SPI bus, with a twist, since each byte sent
> > must be prefixed by a bit, which needs an 9-bits-per-word SPI controller,
> > which is quite rare. Else, you would need to bitbang it.
> 
> It's possible to support SPI controllers that can't do 9-bit by using
> 8-bit mode and blocks of 9 bytes to send 8x 9-bit words padded with
> zeroes. Zero is MIPI DCS no-op command.

Ah, yes, that makes sense. Thanks for the hint.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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