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

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Message-ID: <34bd65923697528b5ee540ef30b31542cfc5ba8e.camel@suse.de>
Date:   Mon, 04 Nov 2019 18:19:45 +0100
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Stefan Wahren <wahrenst@....net>, catalin.marinas@....com,
        devicetree@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Eric Anholt <eric@...olt.net>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] ARM: dts: bcm2711: force CMA into first GB of memory

On Mon, 2019-11-04 at 18:09 +0100, Stefan Wahren wrote:
> Hi Nicolas,
> 
> Am 04.11.19 um 14:54 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>
> 
> do you want this in Linux 5.5 via devicetree/fixes? In this case please
> add an fixes tag.

This has to go into v5.5 if the second patch is accepted. That said I can't add
a fixes tag as the code being fixed isn't yet in linus' tree.

Any suggestions? Maybe go through Catalin's tree?

> Otherwise this will be queued for Linux 5.6.
> 
> > ---
> >  arch/arm/boot/dts/bcm2711-rpi-4-b.dts | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> > 
> > diff --git a/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
> > b/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
> > index cccc1ccd19be..3c7833e9005a 100644
> > --- a/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
> > +++ b/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
> > @@ -19,6 +19,25 @@
> >  		reg = <0 0 0>;
> >  	};
> > 
> > +	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
> > +		 * 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;
> > +		};
> > +	};
> > +
> 
> i think this is a SoC-specific issue not a board specifc one. Please
> move this to bcm2711.dtsi

Noted, thanks!

Regards,
Nicolas


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