linux-kernel - Re: [PATCH drm-misc-next] rockchip/drm: vop2: don't check color_mgmt_changed in atomic

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Message-Id: <DAEVDSTMWI1E.J454VZN0R9MA@cknow.org>
Date: Thu, 05 Jun 2025 22:08:29 +0200
From: "Diederik de Haas" <didi.debian@...ow.org>
To: "Piotr Zalewski" <pZ010001011111@...ton.me>, <hjc@...k-chips.com>,
 <heiko@...ech.de>, <andy.yan@...k-chips.com>
Cc: <maarten.lankhorst@...ux.intel.com>, <mripard@...nel.org>,
 <tzimmermann@...e.de>, <airlied@...il.com>, <simona@...ll.ch>, "Dang Huynh"
 <danct12@...eup.net>, <dri-devel@...ts.freedesktop.org>,
 <linux-arm-kernel@...ts.infradead.org>,
 <linux-rockchip@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH drm-misc-next] rockchip/drm: vop2: don't check
 color_mgmt_changed in atomic_enable

Hi Piotr,

Since kernel 6.14-rc1 I have the problem that visual output is no longer
shown on my PineTab2 and a ``git bisect`` pointed to this patch/commit
as the culprit. What is important to note is that ``CONFIG_DRM=m`` seems
to be required as the problem does not occur with ``CONFIG_DRM=y``.

Near the end of my bisect session, something interesting occurred.
I was booted into a 'bad' kernel (ie no visual output) and when I
started to build my final kernel, I closed the lid of the PineTab2 which
made it go into suspend. When my final kernel was built, I opened the
lid again, which made it resume, to transfer my final kernel to it.
And much to my surprise, I then did have visual output.
When I read the (below) commit message of the 'offending' commit, it may
not be such a surprise after all.

When I build a (new) 6.14-rc1 kernel with a revert of this commit on
top, then I did not have the above mentioned problem, confirming this
commit was the 'bad' commit.

I did try it on a Quartz64-B (also rk3566) and it did not have any issue
(output via HDMI).
I don't know what the cause for this issue is, hopefully you do.

Cheers,
  Diederik

On Fri Dec 6, 2024 at 8:26 PM CET, Piotr Zalewski wrote:
> Remove color_mgmt_changed check from vop2_crtc_atomic_try_set_gamma to
> allow gamma LUT rewrite during modeset when coming out of suspend. Add
> a check for color_mgmt_changed directly in vop2_crtc_atomic_flush.
>
> This patch fixes the patch adding gamma LUT support for vop2 [1].
>
> [1] https://lore.kernel.org/linux-rockchip/20241101185545.559090-3-pZ010001011111@proton.me/
>
> Suggested-by: Andy Yan <andy.yan@...k-chips.com>
> Signed-off-by: Piotr Zalewski <pZ010001011111@...ton.me>
> ---
>  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> index 0c8ec7220fbe..d259f1c6571d 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> @@ -1601,7 +1601,7 @@ static void vop2_crtc_atomic_try_set_gamma(struct vop2 *vop2,
>  					   struct drm_crtc *crtc,
>  					   struct drm_crtc_state *crtc_state)
>  {
> -	if (!vop2->lut_regs || !crtc_state->color_mgmt_changed)
> +	if (!vop2->lut_regs)
>  		return;
>  
>  	if (!crtc_state->gamma_lut) {
> @@ -2669,7 +2669,7 @@ static void vop2_crtc_atomic_flush(struct drm_crtc *crtc,
>  	struct vop2 *vop2 = vp->vop2;
>  
>  	/* In case of modeset, gamma lut update already happened in atomic enable */
> -	if (!drm_atomic_crtc_needs_modeset(crtc_state))
> +	if (!drm_atomic_crtc_needs_modeset(crtc_state) && crtc_state->color_mgmt_changed)
>  		vop2_crtc_atomic_try_set_gamma_locked(vop2, vp, crtc, crtc_state);
>  
>  	vop2_post_config(crtc);

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