On 10/31/23 16:40, Emil Renner Berthing wrote: > Cristian Ciocaltea wrote: >> From: Emil Renner Berthing <emil.renner.berthing@xxxxxxxxxxxxx> >> >> The StarFive JH7100 SoC has non-coherent device DMAs, but most drivers >> expect to be able to allocate coherent memory for DMA descriptors and >> such. However on the JH7100 DDR memory appears twice in the physical >> memory map, once cached and once uncached: >> >> 0x00_8000_0000 - 0x08_7fff_ffff : Off chip DDR memory, cached >> 0x10_0000_0000 - 0x17_ffff_ffff : Off chip DDR memory, uncached >> >> To use this uncached region we create a global DMA memory pool there and >> reserve the corresponding area in the cached region. >> >> However the uncached region is fully above the 32bit address limit, so add >> a dma-ranges map so the DMA address used for peripherals is still in the >> regular cached region below the limit. > > Adding these nodes to the device tree won't actually do anything without > enabling CONFIG_DMA_GLOBAL_POOL as is done here: > > https://github.com/esmil/linux/commit/e14ad9ff67fd51dcc76415d4cc7f3a30ffcba379 Should I pick this up for v3 or maybe it would be better to be handled as part of your ccache series? Thanks, Cristian >> >> Link: https://github.com/starfive-tech/JH7100_Docs/blob/main/JH7100%20Data%20Sheet%20V01.01.04-EN%20(4-21-2021).pdf >> Signed-off-by: Emil Renner Berthing <emil.renner.berthing@xxxxxxxxxxxxx> >> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx> >> --- >> .../boot/dts/starfive/jh7100-common.dtsi | 24 +++++++++++++++++++ >> 1 file changed, 24 insertions(+) >> >> diff --git a/arch/riscv/boot/dts/starfive/jh7100-common.dtsi b/arch/riscv/boot/dts/starfive/jh7100-common.dtsi >> index b93ce351a90f..504c73f01f14 100644 >> --- a/arch/riscv/boot/dts/starfive/jh7100-common.dtsi >> +++ b/arch/riscv/boot/dts/starfive/jh7100-common.dtsi >> @@ -39,6 +39,30 @@ led-ack { >> label = "ack"; >> }; >> }; >> + >> + reserved-memory { >> + #address-cells = <2>; >> + #size-cells = <2>; >> + ranges; >> + >> + dma-reserved { >> + reg = <0x0 0xfa000000 0x0 0x1000000>; >> + no-map; >> + }; >> + >> + linux,dma { >> + compatible = "shared-dma-pool"; >> + reg = <0x10 0x7a000000 0x0 0x1000000>; >> + no-map; >> + linux,dma-default; >> + }; >> + }; >> + >> + soc { >> + dma-ranges = <0x00 0x80000000 0x00 0x80000000 0x00 0x7a000000>, >> + <0x00 0xfa000000 0x10 0x7a000000 0x00 0x01000000>, >> + <0x00 0xfb000000 0x00 0xfb000000 0x07 0x85000000>; >> + }; >> }; >> >> &gpio { >> -- >> 2.42.0 >>
