linux-kernel - Re: [PATCH v3] rockchip/drm: vop2: add support for gamma LUT

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Message-ID: <CAPj87rPwJ-vRTsjM1rWRj1gyjbJM_ryrkTiPRBF3ZF1D7TVDYw@mail.gmail.com>
Date: Thu, 25 Jul 2024 11:28:58 +0100
From: Daniel Stone <daniel@...ishbar.org>
To: Piotr Zalewski <pZ010001011111@...ton.me>
Cc: "airlied@...il.com" <airlied@...il.com>, "andy.yan@...k-chips.com" <andy.yan@...k-chips.com>, 
	"daniel@...ll.ch" <daniel@...ll.ch>, 
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>, "heiko@...ech.de" <heiko@...ech.de>, 
	"hjc@...k-chips.com" <hjc@...k-chips.com>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"linux-rockchip@...ts.infradead.org" <linux-rockchip@...ts.infradead.org>, 
	"maarten.lankhorst@...ux.intel.com" <maarten.lankhorst@...ux.intel.com>, 
	"mripard@...nel.org" <mripard@...nel.org>, "tzimmermann@...e.de" <tzimmermann@...e.de>
Subject: Re: [PATCH v3] rockchip/drm: vop2: add support for gamma LUT

Hi Piotr,

On Wed, 24 Jul 2024 at 23:06, Piotr Zalewski <pZ010001011111@...ton.me> wrote:
> Add support for gamma LUT in VOP2 driver. The implementation is based on
> the one found in VOP driver and modified to be compatible with VOP2. Blue
> and red channels in gamma LUT register write were swapped with respect to
> how gamma LUT values are written in VOP. Write of the current video port id
> to VOP2_SYS_LUT_PORT_SEL register was added before the write of DSP_LUT_EN
> bit. Gamma size is set and drm color management is enabled for each video
> port's CRTC except ones which have no associated device. Tested on RK3566
> (Pinetab2).

Thanks a lot for doing this!

> +static void vop2_crtc_gamma_set(struct vop2 *vop2, struct drm_crtc *crtc,
> +                               struct drm_crtc_state *old_state)
> +{
> +       [...]
> +
> +       vop2_lock(vop2);
> +       vop2_crtc_write_gamma_lut(vop2, crtc);
> +       vop2_writel(vp->vop2, RK3568_LUT_PORT_SEL, vp->id);
> +
> +       vop2_vp_dsp_lut_enable(vp);
> +
> +       vop2_cfg_done(vp);
> +       vop2_unlock(vop2);
> +}
>
> @@ -2060,6 +2159,9 @@ static void vop2_crtc_atomic_enable(struct drm_crtc *crtc,
>         drm_crtc_vblank_on(crtc);
>
>         vop2_unlock(vop2);
> +
> +       if (crtc->state->gamma_lut)
> +               vop2_crtc_gamma_set(vop2, crtc, old_state);
>  }

In the atomic_enable callback, we are already holding the VOP lock,
and waiting to set cfg_done etc - we then do it all over again here.
This should all be atomic, so that we configure the LUT whilst doing
the setup, and then only call cfg_done once, to avoid showing the user
intermediate states which only later converge on the desired final
state.

Cheers,
Daniel