linux-kernel - [PATCH 1/3] arm64: dts: ti: k3-am62x-sk-common: Reserve 128MiB of global CMA

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Message-ID: <20240613150902.2173582-2-devarsht@ti.com>
Date: Thu, 13 Jun 2024 20:39:00 +0530
From: Devarsh Thakkar <devarsht@...com>
To: <nm@...com>, <vigneshr@...com>, <kristo@...nel.org>, <robh@...nel.org>,
        <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC: <praneeth@...com>, <a-bhatia1@...com>, <j-luthra@...com>,
        <b-brnich@...com>, <detheridge@...com>, <p-mantena@...com>,
        <vijayp@...com>, <devarsht@...com>
Subject: [PATCH 1/3] arm64: dts: ti: k3-am62x-sk-common: Reserve 128MiB of global CMA

Reserve 128MiB of global CMA which is also marked as re-usable
so that OS can also use the same if peripheral drivers are not using the
same.

AM62x supports multimedia components such as GPU, dual Display and Camera.
Assuming the worst-case scenario where all 3 are run in parallel below
is the calculation :

1) OV5640 camera sensor supports 1920x1080 resolution
-> 1920 width x 1080 height x 2 bytesperpixel x 8 buffers
   (default in yavta) : 32MiB

2) 1920x1200 Microtips LVDS panel supported
-> 1920 width x 1080 height x 4 bytesperpixel x 2 buffers :
   16 MiB

3) 1920x1080 HDMI display supported
-> 1920 width x 1080 height x 4 bytesperpixel x 2 buffers :
   15.82 MiB which is ~16 MiB

4) IMG GPU shares with display allocated buffers while rendering
   but in case some dedicated operation viz color conversion,
   keeping same window of ~16 MiB for GPU too.

Total is 80 MiB and adding 32 MiB for other peripherals and extra
16 MiB to keep as buffer for fragmentation thus rounding total to 128
MiB.

Signed-off-by: Devarsh Thakkar <devarsht@...com>
---
 arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi
index f4948b937627..52231bfe60fe 100644
--- a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi
+++ b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi
@@ -48,6 +48,14 @@ ramoops@...00000 {
 			pmsg-size = <0x8000>;
 		};
 
+		/* global cma region */
+		linux,cma {
+			compatible = "shared-dma-pool";
+			reusable;
+			size = <0x00 0x8000000>;
+			linux,cma-default;
+		};
+
 		secure_tfa_ddr: tfa@...80000 {
 			reg = <0x00 0x9e780000 0x00 0x80000>;
 			alignment = <0x1000>;
-- 
2.39.1