linux-kernel - RE: [PATCH v5 0/8] drm: rcar-du: Add Color Management Module (CMM)

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Message-ID: <OSAPR01MB2114E435BCF6B1F47F331F298BB10@OSAPR01MB2114.jpnprd01.prod.outlook.com>
Date:   Wed, 27 May 2020 07:40:14 +0000
From:   Gotthard Voellmeke <gotthard.voellmeke@...esas.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        "REE erosca@...ADIT-JV.COM" <erosca@...ADIT-JV.COM>
CC:     Jacopo Mondi <jacopo+renesas@...ndi.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Simon Horman <horms@...ge.net.au>,
        Ulrich Hecht <uli+renesas@...nd.eu>,
        "VenkataRajesh.Kalakodima@...bosch.com" 
        <VenkataRajesh.Kalakodima@...bosch.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        KOJI MATSUOKA <koji.matsuoka.xm@...esas.com>,
        "muroya@....co.jp" <muroya@....co.jp>,
        "Harsha.ManjulaMallikarjun@...bosch.com" 
        <Harsha.ManjulaMallikarjun@...bosch.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Sean Paul <seanpaul@...omium.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Michael Dege <michael.dege@...esas.com>,
        "REE efriedrich@...ADIT-JV.COM" <efriedrich@...ADIT-JV.COM>,
        Michael Rodin <mrodin@...adit-jv.com>,
        "ChaitanyaKumar.Borah@...bosch.com" 
        <ChaitanyaKumar.Borah@...bosch.com>,
        Eugeniu Rosca <roscaeugeniu@...il.com>,
        Hien Dang <hien.dang.eb@...esas.com>,
        Michael Klein <michael.klein@...esas.com>
Subject: RE: [PATCH v5 0/8] drm: rcar-du: Add Color Management Module (CMM)

Added Hien-san, Michael K. from Renesas.

-----Original Message-----
From: Geert Uytterhoeven <geert@...ux-m68k.org>
Sent: Mittwoch, 27. Mai 2020 09:35
To: REE erosca@...ADIT-JV.COM <erosca@...ADIT-JV.COM>
Cc: Jacopo Mondi <jacopo+renesas@...ndi.org>; Laurent Pinchart <laurent.pinchart@...asonboard.com>; Kieran Bingham <kieran.bingham+renesas@...asonboard.com>; Simon Horman <horms@...ge.net.au>; Ulrich Hecht <uli+renesas@...nd.eu>; VenkataRajesh.Kalakodima@...bosch.com; David Airlie <airlied@...ux.ie>; Daniel Vetter <daniel@...ll.ch>; KOJI MATSUOKA <koji.matsuoka.xm@...esas.com>; muroya@....co.jp; Harsha.ManjulaMallikarjun@...bosch.com; Ezequiel Garcia <ezequiel@...labora.com>; Sean Paul <seanpaul@...omium.org>; Linux-Renesas <linux-renesas-soc@...r.kernel.org>; DRI Development <dri-devel@...ts.freedesktop.org>; Linux Kernel Mailing List <linux-kernel@...r.kernel.org>; Michael Dege <michael.dege@...esas.com>; Gotthard Voellmeke <gotthard.voellmeke@...esas.com>; REE efriedrich@...ADIT-JV.COM <efriedrich@...ADIT-JV.COM>; Michael Rodin <mrodin@...adit-jv.com>; ChaitanyaKumar.Borah@...bosch.com; Eugeniu Rosca <roscaeugeniu@...il.com>
Subject: Re: [PATCH v5 0/8] drm: rcar-du: Add Color Management Module (CMM)

Hi Eugeniu,

On Wed, May 27, 2020 at 9:16 AM Eugeniu Rosca <erosca@...adit-jv.com> wrote:
> On Tue, Oct 15, 2019 at 12:46:13PM +0200, Jacopo Mondi wrote:
> > CMM functionalities are retained between suspend/resume cycles (tested with
> > suspend-to-idle) without requiring a re-programming of the LUT tables.
>
> Hmm. Is this backed up by any statement in the HW User's manual?
> This comes in contrast with the original Renesas CMM implementation [**]
> which does make use of suspend (where the freeze actually happens).
>
> Can we infer, based on your statement, that we could also get rid of
> the suspend callback in [**]?

While the CMM state will be retained across suspend-to-idle, I'm quite
sure it will be lost by suspend-to-RAM, at least on the Salvator-X(S),
ULCB, and Ebisu development boards, as PSCI will ask the BD9571WMV
regulator to power down the R-Car SoC.

So IMHO we do need suspend/resume handling.

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


Renesas Electronics Europe GmbH, Geschaeftsfuehrer/President: Carsten Jauch, Sitz der Gesellschaft/Registered office: Duesseldorf, Arcadiastrasse 10, 40472 Duesseldorf, Germany, Handelsregister/Commercial Register: Duesseldorf, HRB 3708 USt-IDNr./Tax identification no.: DE 119353406 WEEE-Reg.-Nr./WEEE reg. no.: DE 14978647