linux-kernel - Re: [PATCH 1/2] dt-bindings: display: Add Sharp Memory LCD bindings

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Message-ID: <3wgrdnpwmss3lpevxmf574pqt4rwttdwadsm6tqaobouw3akor@v6z76j5yzdmu>
Date: Sun, 28 Jul 2024 10:52:31 -0400
From: Alex Lanzano <lanzano.alex@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: mehdi.djait@...tlin.com, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: display: Add Sharp Memory LCD bindings

On Sun, Jul 28, 2024 at 04:43:42PM GMT, Krzysztof Kozlowski wrote:
> On 28/07/2024 14:56, Alex Lanzano wrote:
> >>>>> +
> >>>>> +  spi-cs-high: true
> >>>>
> >>>> You can drop it.
> >>>>
> >>>
> >>> This is a required property in order for the display to function correctly.
> >>> But I have no issues removing it if there's a better place to document it.
> >>
> >> The sharp LCD device or the board (e.g. via some inversion)?
> >>
> > 
> > The sharp LCD device itself.
> > 
> > https://cdn.sparkfun.com/assets/d/e/8/9/7/LS013B7DH03_datasheet.pdf
> > Page 16 of the PDF below shows the timing chart for it if interested
> 
> OK, so you enforce chip select as always high and then someone comes
> with a board which has a inversion and expect the SoC to drive it low,
> as usually? In such system this would not work, would it?
> 
> IOW, I think this is the first case where you require specific CS high
> and this should make you think why...

Ahh I see what you mean! I'll remove it.

Best regard,
Alex