linux-kernel - Re: [PATCH v2 02/10] drm/rcar-du: Write DPTSR only if there are more than one crtc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMuHMdVHRWbeQ8UF-xsKuxUNwHc5_kVwSgrTfOkwFFG5vG7fwA@mail.gmail.com>
Date: Thu, 5 Dec 2024 15:16:27 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
	Kieran Bingham <kieran.bingham+renesas@...asonboard.com>, 
	Andrzej Hajda <andrzej.hajda@...el.com>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Robert Foss <rfoss@...nel.org>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Geert Uytterhoeven <geert+renesas@...der.be>, Magnus Damm <magnus.damm@...il.com>, 
	Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	LUU HOAI <hoai.luu.ub@...esas.com>, Jagan Teki <jagan@...rulasolutions.com>, 
	Sam Ravnborg <sam@...nborg.org>, Biju Das <biju.das.jz@...renesas.com>, 
	dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>, linux-clk@...r.kernel.org, 
	Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>, 
	Jacopo Mondi <jacopo.mondi@...asonboard.com>
Subject: Re: [PATCH v2 02/10] drm/rcar-du: Write DPTSR only if there are more
 than one crtc

Hi Tomi,

CC Jacopo

On Thu, Dec 5, 2024 at 2:45 PM Tomi Valkeinen
<tomi.valkeinen@...asonboard.com> wrote:
> From: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>
>
> Currently the driver always writes DPTSR when setting up the hardware.
> However, the register is only meaningful when there are more than one
> crtc, and the only SoC with one crtc, V3M, does not have the register
> mentioned in its documentation.

R-Car V3H/V3H_2, too.

>
> So move the write behind a condition.
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>
> ---
>  drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c b/drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c
> index 2ccd2581f544..0fbf6abbde6e 100644
> --- a/drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c
> +++ b/drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c
> @@ -185,11 +185,13 @@ static void rcar_du_group_setup(struct rcar_du_group *rgrp)
>                 dorcr |= DORCR_PG1T | DORCR_DK1S | DORCR_PG1D_DS1;
>         rcar_du_group_write(rgrp, DORCR, dorcr);
>
> -       /* Apply planes to CRTCs association. */
> -       mutex_lock(&rgrp->lock);
> -       rcar_du_group_write(rgrp, DPTSR, (rgrp->dptsr_planes << 16) |
> -                           rgrp->dptsr_planes);
> -       mutex_unlock(&rgrp->lock);
> +       if (rgrp->num_crtcs > 1) {
> +               /* Apply planes to CRTCs association. */
> +               mutex_lock(&rgrp->lock);
> +               rcar_du_group_write(rgrp, DPTSR, (rgrp->dptsr_planes << 16) |
> +                                   rgrp->dptsr_planes);
> +               mutex_unlock(&rgrp->lock);
> +       }

This is per group, not per DU, right?
The second group on R-Car M3-W/M3-W+ has a single channel, hence no
DPTSR2 register.
The second group on R-Car M3-N has a single channel, but it's actually
the second physical channel in the group, and thus does have DPTSR2.

And apparently we had this discussion before...
https://lore.kernel.org/all/CAMuHMdXxf4oePnyLvp84OhSa+wdehCNJBXnhjYO7-1VxpBJ7eQ@mail.gmail.com

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds