linux-kernel - Re: [PATCH v3 13/14] drm: rcar-du: kms: Update CMM in atomic commit tail

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Message-ID: <20190827144421.vbcoizfjxj5ashv2@uno.localdomain>
Date:   Tue, 27 Aug 2019 16:44:21 +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, Ulrich Hecht <uli+renesas@...nd.eu>
Subject: Re: [PATCH v3 13/14] drm: rcar-du: kms: Update CMM in atomic commit
 tail

HI Laurent,

On Tue, Aug 27, 2019 at 03:19:27AM +0300, Laurent Pinchart wrote:
> On Tue, Aug 27, 2019 at 03:00:17AM +0300, Laurent Pinchart wrote:
> > Hi Jacopo,
> >
> > Thank you for the patch.
> >
> > On Sun, Aug 25, 2019 at 03:51:53PM +0200, Jacopo Mondi wrote:
> > > Update CMM settings at in the atomic commit tail helper method.
> > >
> > > The CMM is updated with new gamma values provided to the driver
> > > in the GAMMA_LUT blob property.
> > >
> > > Reviewed-by: Ulrich Hecht <uli+renesas@...nd.eu>
> > > Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> > > Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> > > ---
> > >  drivers/gpu/drm/rcar-du/rcar_du_kms.c | 35 +++++++++++++++++++++++++++
> > >  1 file changed, 35 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> > > index 61ca1d3c379a..047fdb982a11 100644
> > > --- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> > > +++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> > > @@ -22,6 +22,7 @@
> > >  #include <linux/of_platform.h>
> > >  #include <linux/wait.h>
> > >
> > > +#include "rcar_cmm.h"
> > >  #include "rcar_du_crtc.h"
> > >  #include "rcar_du_drv.h"
> > >  #include "rcar_du_encoder.h"
> > > @@ -368,6 +369,37 @@ rcar_du_fb_create(struct drm_device *dev, struct drm_file *file_priv,
> > >   * Atomic Check and Update
> > >   */
> > >
> > > +static void rcar_du_atomic_commit_update_cmm(struct drm_crtc *crtc,
> > > +					     struct drm_crtc_state *old_state)
> > > +{
> > > +	struct rcar_du_crtc *rcrtc = to_rcar_crtc(crtc);
> > > +	struct rcar_cmm_config cmm_config = {};
> > > +
> > > +	if (!rcrtc->cmm || !crtc->state->color_mgmt_changed)
> > > +		return;
> > > +
> > > +	if (!crtc->state->gamma_lut) {
> > > +		cmm_config.lut.enable = false;
> > > +		rcar_cmm_setup(rcrtc->cmm, &cmm_config);
> > > +
> > > +		return;
> > > +	}
> > > +
> > > +	cmm_config.lut.enable = true;
> > > +	cmm_config.lut.table = (struct drm_color_lut *)
> > > +			       crtc->state->gamma_lut->data;
> > > +
> > > +	/* Set LUT table size to 0 if entries should not be updated. */
> > > +	if (!old_state->gamma_lut ||
> > > +	    old_state->gamma_lut->base.id != crtc->state->gamma_lut->base.id)
> > > +		cmm_config.lut.size = crtc->state->gamma_lut->length
> > > +				    / sizeof(cmm_config.lut.table[0]);
> >
> > It has just occurred to me that the hardware only support LUTs of

Where did you find this strict requirement ? I have tried programming
less than 256 entries in the 1-D LUT table, and it seems to me things
are working fine (from a visual inspection of the output image, I
don't see much differences from when I program the full table, maybe
that's an indication something is bad?)

Thanks
   j
> > exactly 256 entries. Should we remove cmm_config.lut.size (simplifying
> > the code in the CMM driver), and add a check to the CRTC .atomic_check()
> > handler to reject invalid LUTs ? Sorry for not having caught this
> > earlier.
>
> Just an additional comment, if we drop the size field, then the
> cmm_config.lut.table pointer should be set to NULL when the LUT contents
> don't need to be updated.
>
> > > +	else
> > > +		cmm_config.lut.size = 0;
> > > +
> > > +	rcar_cmm_setup(rcrtc->cmm, &cmm_config);
> > > +}
> > > +
> > >  static int rcar_du_atomic_check(struct drm_device *dev,
> > >  				struct drm_atomic_state *state)
> > >  {
> > > @@ -410,6 +442,9 @@ static void rcar_du_atomic_commit_tail(struct drm_atomic_state *old_state)
> > >  			rcdu->dpad1_source = rcrtc->index;
> > >  	}
> > >
> > > +	for_each_old_crtc_in_state(old_state, crtc, crtc_state, i)
> > > +		rcar_du_atomic_commit_update_cmm(crtc, crtc_state);
> > > +
> > >  	/* Apply the atomic update. */
> > >  	drm_atomic_helper_commit_modeset_disables(dev, old_state);
> > >  	drm_atomic_helper_commit_planes(dev, old_state,
> >
> > --
> > Regards,
> >
> > Laurent Pinchart
>
> --
> Regards,
>
> Laurent Pinchart

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