linux-kernel - [PATCH] arm64: dts: imx8mn: Slow default video

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Date: Sun, 11 Feb 2024 17:15:08 -0600
From: Adam Ford <aford173@...il.com>
To: linux-arm-kernel@...ts.infradead.org
Cc: marex@...x.de,
	aford@...conembedded.com,
	Adam Ford <aford173@...il.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	NXP Linux Team <linux-imx@....com>,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] arm64: dts: imx8mn: Slow default video_pll clock rate

Since commit 8208181fe536 ("clk: imx: composite-8m:
Add imx8m_divider_determine_rate") the lcdif controller has
had the ability to set the disp_pixel_clk rate which propagates
up the tree and sets the video_pll rate automatically.

By setting this value low, it will force the recalculation of
video_pll to the lowest rate needed by lcdif instead of
dividing a larger clock down to the desired clock speed. This
has the  advantage of being able to lower the video_pll rate
from 594MHz to 148.5MHz when operating at 1080p. It can go even
lower when operating at lower resolutions and refresh rates.

Signed-off-by: Adam Ford <aford173@...il.com>

diff --git a/arch/arm64/boot/dts/freescale/imx8mn.dtsi b/arch/arm64/boot/dts/freescale/imx8mn.dtsi
index 136e75c51251..932c8b05c75f 100644
--- a/arch/arm64/boot/dts/freescale/imx8mn.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mn.dtsi
@@ -1168,7 +1168,7 @@ disp_blk_ctrl: blk-ctrl@...28000 {
 							 <&clk IMX8MN_SYS_PLL1_800M>;
 				assigned-clock-rates = <266000000>,
 						       <24000000>,
-						       <594000000>,
+						       <24000000>,
 						       <500000000>,
 						       <200000000>;
 				#power-domain-cells = <1>;
-- 
2.43.0