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Date: Thu, 5 Dec 2019 16:08:08 -0800 From: Florian Fainelli <f.fainelli@...il.com> To: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>, Rob Herring <robh+dt@...nel.org>, Mark Rutland <mark.rutland@....com>, Eric Anholt <eric@...olt.net>, Stefan Wahren <wahrenst@....net>, Florian Fanelli <f.fainelli@...il.com> Cc: mbrugger@...e.com, phil@...pberrypi.org, devicetree@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com, linux-rpi-kernel@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] ARM: dts: bcm2711: fix soc's node dma-ranges On 12/4/19 4:56 AM, Nicolas Saenz Julienne wrote: > Raspberry Pi's firmware has a feature to select how much memory to > reserve for its GPU called 'gpu_mem'. The possible values go from 16MB > to 944MB, with a default of 64MB. This memory resides in the topmost > part of the lower 1GB memory area and grows bigger expanding towards the > begging of memory. > > It turns out that with low 'gpu_mem' values (16MB and 32MB) the size of > the memory available to the system in the lower 1GB area can outgrow the > interconnect's dma-range as its size was selected based on the maximum > system memory available given the default gpu_mem configuration. This > makes that memory slice unavailable for DMA. And may cause nasty kernel > warnings if CMA happens to include it. > > Change soc's dma-ranges to really reflect it's HW limitation, which is > being able to only DMA to the lower 1GB area. > > Fixes: 7dbe8c62ceeb ("ARM: dts: Add minimal Raspberry Pi 4 support") > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de> > --- > > NOTE: I'd appreciate if someone from the RPi foundation commented on > this as it's something that I'll propose to be backported to their tree. I don't think our additional DTS changes will be merged until -rc1 is cut, so we have some time to figure this one out. Thanks > > arch/arm/boot/dts/bcm2711.dtsi | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/boot/dts/bcm2711.dtsi b/arch/arm/boot/dts/bcm2711.dtsi > index 5b61cd915f2b..d6a0e350b7b4 100644 > --- a/arch/arm/boot/dts/bcm2711.dtsi > +++ b/arch/arm/boot/dts/bcm2711.dtsi > @@ -43,7 +43,7 @@ soc { > <0x7c000000 0x0 0xfc000000 0x02000000>, > <0x40000000 0x0 0xff800000 0x00800000>; > /* Emulate a contiguous 30-bit address range for DMA */ > - dma-ranges = <0xc0000000 0x0 0x00000000 0x3c000000>; > + dma-ranges = <0xc0000000 0x0 0x00000000 0x40000000>; > > /* > * This node is the provider for the enable-method for > -- Florian
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