4.20-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 5ec17af7ead09701e23d2065e16db6ce4e137289 ]
The Intel EG20T Platform Controller Hub used on the MIPS Boston development board supports prefetching memory to optimize DMA transfers. Unfortunately for unknown reasons this doesn't work well with some MIPS CPUs such as the P6600, particularly when using an I/O Coherence Unit (IOCU) to provide cache-coherent DMA. In these systems it is common for DMA data to be lost, resulting in broken access to EG20T devices such as the MMC or SATA controllers.
Support for a DT property to configure the prefetching was added a while back by commit 549ce8f134bd ("misc: pch_phub: Read prefetch value from device tree if passed") but we never added the DT snippet to make use of it. Add that now in order to disable the prefetching & fix DMA on the affected systems.
Signed-off-by: Paul Burton paul.burton@mips.com Patchwork: https://patchwork.linux-mips.org/patch/21068/ Cc: linux-mips@linux-mips.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/mips/boot/dts/img/boston.dts | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/arch/mips/boot/dts/img/boston.dts b/arch/mips/boot/dts/img/boston.dts index 65af3f6ba81c..84328afa3a55 100644 --- a/arch/mips/boot/dts/img/boston.dts +++ b/arch/mips/boot/dts/img/boston.dts @@ -141,6 +141,12 @@ #size-cells = <2>; #interrupt-cells = <1>;
+ eg20t_phub@2,0,0 { + compatible = "pci8086,8801"; + reg = <0x00020000 0 0 0 0>; + intel,eg20t-prefetch = <0>; + }; + eg20t_mac@2,0,1 { compatible = "pci8086,8802"; reg = <0x00020100 0 0 0 0>;