Re: [RESEND PATCH v2 3/6] ARM: dts: stm32: support display on stm32f746-disco board

[Dario Binacchi <dario.binacchi@amarulasolutions.com>]

Hi Jagan,

On Wed, Jun 7, 2023 at 8:43 AM Jagan Teki <jagan@amarulasolutions.com> wrote:
>
> On Wed, Jun 7, 2023 at 12:01 PM 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 = <0xC0000000 0x800000>;
> >         };
> >
> > +       reserved-memory {
> > +               #address-cells = <1>;
> > +               #size-cells = <1>;
> > +               ranges;
> > +
> > +               linux,cma {
> > +                       compatible = "shared-dma-pool";
> > +                       no-map;
> > +                       size = <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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