linux-kernel - [PATCH 1/2] ARM: dts: stm32: Setup 4M bytes reserved memory for mmap

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Date:   Mon,  8 Jun 2020 16:30:37 +0800
From:   dillon.minfei@...il.com
To:     robh+dt@...nel.org, mcoquelin.stm32@...il.com,
        alexandre.torgue@...com, linux@...linux.org.uk,
        vladimir.murzin@....com, kstewart@...uxfoundation.org,
        allison@...utok.net, info@...ux.net, tglx@...utronix.de
Cc:     devicetree@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        dillon min <dillon.minfei@...il.com>
Subject: [PATCH 1/2] ARM: dts: stm32: Setup 4M bytes reserved memory for mmap

From: dillon min <dillon.minfei@...il.com>

To mmap a framebuffer or v4l2 buffer from kernel to userspace on
no-mmu platform, we need rely on 'arm_nommu_dma_ops' from
arch/arm/mm/dma-mapping-nommu.c , so setup 4M bytes memory
reserved for this purpose.

Signed-off-by: dillon min <dillon.minfei@...il.com>
---
 arch/arm/boot/dts/stm32f469-disco.dts | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/arm/boot/dts/stm32f469-disco.dts b/arch/arm/boot/dts/stm32f469-disco.dts
index 9397db0c43de..082b24ee81f7 100644
--- a/arch/arm/boot/dts/stm32f469-disco.dts
+++ b/arch/arm/boot/dts/stm32f469-disco.dts
@@ -65,6 +65,20 @@
 		reg = <0x00000000 0x1000000>;
 	};
 
+	reserved-memory {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges;
+
+		linux,dma {
+			compatible = "shared-dma-pool";
+			size = <0x400000>;
+			no-map;
+			linux,dma-default;
+		};
+
+	};
+
 	aliases {
 		serial0 = &usart3;
 	};
-- 
2.7.4