linux-kernel - Re: Re:Re:[PATCH v5] rockchip/drm: vop2: add support for gamma LUT

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Message-ID: <CAPj87rOmPyat12S4WUixiUBAsuAEEbyNX5VY2JS+wn5a1jux0A@mail.gmail.com>
Date: Wed, 16 Oct 2024 13:27:06 +0100
From: Daniel Stone <daniel@...ishbar.org>
To: Andy Yan <andyshrk@....com>
Cc: Piotr Zalewski <pZ010001011111@...ton.me>, hjc@...k-chips.com, heiko@...ech.de, 
	andy.yan@...k-chips.com, maarten.lankhorst@...ux.intel.com, 
	mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch, 
	dri-devel@...ts.freedesktop.org, linux-arm-kernel@...ts.infradead.org, 
	linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	skhan@...uxfoundation.org, Dragan Simic <dsimic@...jaro.org>, 
	Diederik de Haas <didi.debian@...ow.org>
Subject: Re: Re:Re:[PATCH v5] rockchip/drm: vop2: add support for gamma LUT

Hi all,

On Wed, 16 Oct 2024 at 02:11, Andy Yan <andyshrk@....com> wrote:
> At 2024-10-16 04:13:40, "Piotr Zalewski" <pZ010001011111@...ton.me> wrote:
> >Ok I get it now. Is such rework correct? - when gamma LUT for rk356x is
> >being set, instead of disabling the LUT before the gamma LUT write for the
> >current CRTC's video port, active video port is selected. Selection is
> >based on if DSP LUT EN bit is set for particular video port. eg:
>
> If the userspace want to set gamma for CRTCx,  then that is indeed where they want to set the
> gamma on。The driver silently sets the gamma on another CRTC, which is not what the user wants.
>
> I think there are two options：
> （1）return a error if gamma is enable on other CRTC， this is what we done in our BSP code[1]
>   (2)  disable the dsp_lut on privious CRTC, then switch to the current CRTC which userspace wants.

1 is the only solution that can work. Silently changing the colour
properties of a separate CRTC is not OK, since this can lead to
displaying incorrect content.

Cheers,
Daniel