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@xxxxxxxxxxxx>
Cc: devicetree@xxxxxxxxxxxxxxx
---
arch/arc/boot/dts/axc001.dtsi | 20 +++++++++++++++++++-
arch/arc/boot/dts/axc003.dtsi | 14 ++++++++++++++
arch/arc/boot/dts/axc003_idu.dtsi | 14 ++++++++++++++
arch/arc/boot/dts/axs10x_mb.dtsi | 2 +-
4 files changed, 48 insertions(+), 2 deletions(-)
diff --git a/arch/arc/boot/dts/axc001.dtsi b/arch/arc/boot/dts/axc001.dtsi
index 420dcfd..ae6162d 100644
--- a/arch/arc/boot/dts/axc001.dtsi
+++ b/arch/arc/boot/dts/axc001.dtsi
@@ -95,6 +95,24 @@
#size-cells = <1>;
ranges = <0x00000000 0x80000000 0x40000000>;
device_type = "memory";
- reg = <0x80000000 0x20000000>; /* 512MiB */
+ reg = <0x80000000 0x1f000000>; /* 512 - 16 MiB */
+ };
+
+ reserved-memory {
+ #address-cells = <1>;
+ #size-cells = <1>;
+ ranges;
+ /*
+ * We just move frame buffer area to the very end of
+ * available DDR. And even though in case of ARC770 there's
+ * no strict requirement for a frame-buffer to be in any
+ * particular location it allows us to use the same
+ * base board's DT node for ARC PGU as for ARc HS38.
+ */
+ frame_buffer: frame_buffer@9f000000 {
+ compatible = "shared-dma-pool";
+ reg = <0x9f000000 0x1000000>;
+ no-map;
+ };
};
};
diff --git a/arch/arc/boot/dts/axc003.dtsi b/arch/arc/boot/dts/axc003.dtsi
index f90fadf..c7a95c2 100644
--- a/arch/arc/boot/dts/axc003.dtsi
+++ b/arch/arc/boot/dts/axc003.dtsi
@@ -100,4 +100,18 @@
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@a0000000 {
+ compatible = "shared-dma-pool";
+ reg = <0xa0000000 0x1000000>;
+ no-map;
+ };
+ };
};
diff --git a/arch/arc/boot/dts/axc003_idu.dtsi b/arch/arc/boot/dts/axc003_idu.dtsi
index 06a9f29..929ec8c 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@a0000000 {
+ compatible = "shared-dma-pool";
+ reg = <0xa0000000 0x1000000>;
+ no-map;
+ };
+ };
};
diff --git a/arch/arc/boot/dts/axs10x_mb.dtsi b/arch/arc/boot/dts/axs10x_mb.dtsi
index 823f15c..64b063d 100644
--- a/arch/arc/boot/dts/axs10x_mb.dtsi
+++ b/arch/arc/boot/dts/axs10x_mb.dtsi
@@ -283,7 +283,7 @@
encoder-slave = <&adv7511>;
clocks = <&pguclk>;
clock-names = "pxlclk";
-
+ memory-region = <&frame_buffer>;
port {
pgu_output: endpoint {
remote-endpoint = <&adv7511_input>;
--
2.5.5
--
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