ARC: [axs10x] Specify reserved memory for frame buffer

Allocation of a frame buffer memory in a special memory region
allows bypassing of so-called IO Coherency aperture
which is typically set as a range 0x8z-0xAz.

I.e. all data traffic to PGU bypasses IO Coherency block
and saves its bandwidth for other peripherals.

Even though for AXS101 (which sorts ARC770 CPU) IOC is not
an option for a sake of keeping one DT description for the
base-board (axs10x_mb.dtsi) we're still defining reserved
memory location in the very end of DDR.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Acked-by: Vineet Gupta <vgupta@synopsys.com>
Cc: devicetree@vger.kernel.org

1 files changed, 14 insertions, 0 deletions

diff --git a/arch/arc/boot/dts/axc003_idu.dtsi b/arch/arc/boot/dts/axc003_idu.dtsi
index 06a9f294a2e6..df9ddb623bfe 100644
--- a/arch/arc/boot/dts/axc003_idu.dtsi
+++ b/arch/arc/boot/dts/axc003_idu.dtsi
@@ -123,4 +123,18 @@
 		device_type = "memory";
 		reg = <0x80000000 0x20000000>;	/* 512MiB */
 	};
+
+	reserved-memory {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges;
+		/*
+		 * Move frame buffer out of IOC aperture (0x8z-0xAz).
+		 */
+		frame_buffer: frame_buffer@be000000 {
+			compatible = "shared-dma-pool";
+			reg = <0xbe000000 0x2000000>;
+			no-map;
+		};
+	};
 };