linux-kernel - Re: [PATCH v3 14/14] drm: rcar-du: Force CMM enablement when resuming

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Date:   Thu, 5 Sep 2019 12:58:09 +0200
From:   Jacopo Mondi <jacopo@...ndi.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Jacopo Mondi <jacopo+renesas@...ndi.org>,
        kieran.bingham+renesas@...asonboard.com, geert@...ux-m68k.org,
        horms@...ge.net.au, uli@...nd.eu, airlied@...ux.ie,
        daniel@...ll.ch, koji.matsuoka.xm@...esas.com, muroya@....co.jp,
        VenkataRajesh.Kalakodima@...bosch.com,
        Harsha.ManjulaMallikarjun@...bosch.com,
        linux-renesas-soc@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 14/14] drm: rcar-du: Force CMM enablement when resuming

Hi Laurent,

On Tue, Aug 27, 2019 at 03:05:17AM +0300, Laurent Pinchart wrote:
> Hi Jacopo,
>
> (Question for Daniel below)
>
> Thank you for the patch.
>
> On Sun, Aug 25, 2019 at 03:51:54PM +0200, Jacopo Mondi wrote:
> > When resuming from system suspend, the DU driver is responsible for
> > reprogramming and enabling the CMM unit if it was in use at the time
> > the system entered the suspend state.
> >
> > Force the color_mgmt_changed flag to true if any of the DRM color
> > transformation properties was set in the CRTC state duplicated at
> > suspend time, as the CMM gets reprogrammed only if said flag is active in
> > the rcar_du_atomic_commit_update_cmm() method.
> >
> > Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> > ---
> >  drivers/gpu/drm/rcar-du/rcar_du_drv.c | 21 +++++++++++++++++++++
> >  1 file changed, 21 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_drv.c b/drivers/gpu/drm/rcar-du/rcar_du_drv.c
> > index 018480a8f35c..6e38495fb78f 100644
> > --- a/drivers/gpu/drm/rcar-du/rcar_du_drv.c
> > +++ b/drivers/gpu/drm/rcar-du/rcar_du_drv.c
> > @@ -17,6 +17,7 @@
> >  #include <linux/slab.h>
> >  #include <linux/wait.h>
> >
> > +#include <drm/drm_atomic.h>
> >  #include <drm/drm_atomic_helper.h>
> >  #include <drm/drm_fb_cma_helper.h>
> >  #include <drm/drm_fb_helper.h>
> > @@ -482,6 +483,26 @@ static int rcar_du_pm_suspend(struct device *dev)
> >  static int rcar_du_pm_resume(struct device *dev)
> >  {
> >  	struct rcar_du_device *rcdu = dev_get_drvdata(dev);
> > +	struct drm_atomic_state *state = rcdu->ddev->mode_config.suspend_state;
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < rcdu->num_crtcs; ++i) {
> > +		struct drm_crtc *crtc = &rcdu->crtcs[i].crtc;
> > +		struct drm_crtc_state *crtc_state;
> > +
> > +		crtc_state = drm_atomic_get_existing_crtc_state(state, crtc);
> > +		if (!crtc_state)
> > +			continue;
>
> Shouldn't you get the new state here ?
>

I have followed the drm_atomic_helper_suspend() call stack, that calls
drm_atomic_helper_duplicate_state() which then assign the crtct state
with drm_atomic_get_crtc_state(), where I read:

       	crtc_state = drm_atomic_get_existing_crtc_state(state, crtc);
        ...
	state->crtcs[index].state = crtc_state;
	state->crtcs[index].old_state = crtc->state;
	state->crtcs[index].new_state = crtc_state;

So state or new_state for the purpose of getting back the crtc state
are the same if I'm not mistaken.

> > +
> > +		/*
> > +		 * Force re-enablement of CMM after system resume if any
> > +		 * of the DRM color transformation properties was set in
> > +		 * the state saved at system suspend time.
> > +		 */
> > +		if (crtc_state->gamma_lut || crtc_state->degamma_lut ||
> > +		    crtc_state->ctm)
>
> We don't support degamma_lut or crm, so I would drop those.

yeah, I added them as it was less code to change when we'll support
them. But for now they could be removed.

>
> With these small issues addressed,
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
>
> Shouldn't we however squash this with the previous patch to avoid
> bisection issues ?
>

Which one in your opinion?
"drm: rcar-du: kms: Update CMM in atomic commit tail" ?
It seems to me they do quite different things though..

Thanks
  j

> > +			crtc_state->color_mgmt_changed = true;
>
> Daniel, is this something that would make sense in the KMS core (or
> helpers) ?
>
> > +	}
> >
> >  	return drm_mode_config_helper_resume(rcdu->ddev);
> >  }
>
> --
> Regards,
>
> Laurent Pinchart

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