linux-kernel - Re: [PATCH v2 1/2] ARM: dts: bcm2711: force CMA into first GB of memory

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Message-ID: <b63a382c72bec9e52ea10f9d41aa45c6b1147eba.camel@suse.de>
Date:   Thu, 07 Nov 2019 10:42:30 +0100
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Stefan Wahren <wahrenst@....net>, catalin.marinas@....com,
        linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Eric Anholt <eric@...olt.net>
Cc:     devicetree@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] ARM: dts: bcm2711: force CMA into first GB of
 memory

On Thu, 2019-11-07 at 07:23 +0100, Stefan Wahren wrote:
> Hi Nicolas,
> 
> Am 06.11.19 um 10:59 schrieb Nicolas Saenz Julienne:
> > arm64 places the CMA in ZONE_DMA32, which is not good enough for the
> > Raspberry Pi 4 since it contains peripherals that can only address the
> > first GB of memory. Explicitly place the CMA into that area.
> > 
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> > 
> > ---
> > 
> > Changes since v1:
> >   - Move into bcm2711.dtsi
> > 
> >  arch/arm/boot/dts/bcm2711.dtsi | 20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> > 
> > diff --git a/arch/arm/boot/dts/bcm2711.dtsi b/arch/arm/boot/dts/bcm2711.dtsi
> > index 1f3acd3363ea..6000a01652fa 100644
> > --- a/arch/arm/boot/dts/bcm2711.dtsi
> > +++ b/arch/arm/boot/dts/bcm2711.dtsi
> > @@ -12,6 +12,26 @@
> > 
> >  	interrupt-parent = <&gicv2>;
> > 
> > +	reserved-memory {
> > +		#address-cells = <2>;
> > +		#size-cells = <1>;
> > +		ranges;
> > +
> > +		/*
> > +		 * arm64 reserves the CMA by default somewhere in ZONE_DMA32,
> > +		 * that's not good enough for the Raspberry Pi 4 as some
> 
> sorry for the nitpicking but i hope the Raspberry Pi 4 B wont be the
> only user of BCM2711.

No worries :)

It's better that way anyway.

> 
> So please s/Raspberry Pi 4/BCM2711/
> 
> Beside that:
> 
> Acked-by: Stefan Wahren <wahrenst@....net>

Thanks!

> 
> > +		 * devices can only address the lower 1G of memory (ZONE_DMA).
> > +		 */
> > +		linux,cma {
> > +			compatible = "shared-dma-pool";
> > +			size = <0x2000000>; /* 32MB */
> > +			alloc-ranges = <0x0 0x00000000 0x40000000>;
> > +			reusable;
> > +			linux,cma-default;
> > +		};
> > +	};
> > +
> > +
> >  	soc {
> >  		/*
> >  		 * Defined ranges:
> 
> _______________________________________________
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> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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