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 <20230607063139.621351-4-dario.binacchi@amarulasolutions.com> <CAMty3ZDCkQ_T+j96iXtMAhkOLFBm=hZHk=sZzSGA=MOQQUOv7g@mail.gmail.com>
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From:   Dario Binacchi <dario.binacchi@amarulasolutions.com>
Date:   Wed, 7 Jun 2023 14:49:36 +0200
Message-ID: <CABGWkvq_DevgJeR+KfBy-4ME+u-iORW93BAT4FTMVRuG0KU1Zg@mail.gmail.com>
Subject: Re: [RESEND PATCH v2 3/6] ARM: dts: stm32: support display on
 stm32f746-disco board
To:     Jagan Teki <jagan@amarulasolutions.com>
Cc:     linux-kernel@vger.kernel.org,
        Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>,
        linux-arm-kernel@lists.infradead.org,
        dri-devel@lists.freedesktop.org,
        Philippe Cornu <philippe.cornu@foss.st.com>,
        Amarula patchwork <linux-amarula@amarulasolutions.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        michael@amarulasolutions.com,
        linux-stm32@st-md-mailman.stormreply.com,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Conor Dooley <conor+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Rob Herring <robh+dt@kernel.org>, devicetree@vger.kernel.org
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Hi Jagan,

On Wed, Jun 7, 2023 at 8:43=E2=80=AFAM Jagan Teki <jagan@amarulasolutions.c=
om> wrote:
>
> On Wed, Jun 7, 2023 at 12:01=E2=80=AFPM Dario Binacchi
> <dario.binacchi@amarulasolutions.com> wrote:
> >
> > Add support to Rocktech RK043FN48H display on stm32f746-disco board.
> >
> > Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
> > ---
> >
> > (no changes since v1)
> >
> >  arch/arm/boot/dts/stm32f746-disco.dts | 51 +++++++++++++++++++++++++++
> >  1 file changed, 51 insertions(+)
> >
> > diff --git a/arch/arm/boot/dts/stm32f746-disco.dts b/arch/arm/boot/dts/=
stm32f746-disco.dts
> > index c11616ed5fc6..cda423b6a874 100644
> > --- a/arch/arm/boot/dts/stm32f746-disco.dts
> > +++ b/arch/arm/boot/dts/stm32f746-disco.dts
> > @@ -60,10 +60,41 @@ memory@c0000000 {
> >                 reg =3D <0xC0000000 0x800000>;
> >         };
> >
> > +       reserved-memory {
> > +               #address-cells =3D <1>;
> > +               #size-cells =3D <1>;
> > +               ranges;
> > +
> > +               linux,cma {
> > +                       compatible =3D "shared-dma-pool";
> > +                       no-map;
> > +                       size =3D <0x80000>;
> > +                       linux,dma-default;
> > +               };
> > +       };
>
> This looks unrelated to display enablement, isn't it?

Without the "reserved-memory" node, it is not possible to allocate
memory for the framebuffer.
I got this error:
stm32-display 40016800.display-controller: [drm] *ERROR* failed to
allocate buffer with size 139264

Thanks and regards,
Dario

>
> Jagan.


--

Dario Binacchi

Senior Embedded Linux Developer

dario.binacchi@amarulasolutions.com

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