Messages in this thread Patch in this message | | | Subject | Re: [PATCH] ARM: dts: bcm2711: fix soc's node dma-ranges | From | Phil Elwell <> | Date | Fri, 6 Dec 2019 10:16:07 +0000 |
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Hi Nicolas,
On 06/12/2019 00:08, Florian Fainelli wrote: > 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@suse.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.
The 0x3c000000 size was a mistake that arose from c0000000 + 3c000000 = fc000000, but that is mixing apples and oranges (actually DMA addresses and host physical addresses). Please correct it as you are proposing.
> > 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 >> > >
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