linux-kernel - [PATCH 3/3] arm64: dts: imx8mm: Slow default video

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Date:   Mon, 27 Nov 2023 22:54:15 -0600
From:   Adam Ford <aford173@...il.com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     aford@...conembeded.com, Adam Ford <aford173@...il.com>,
        Rob Herring <robh+dt@...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 3/3] arm64: dts: imx8mm: Slow default video_pll1 clock rate

Since commit 8208181fe536 ("clk: imx: composite-8m:
Add imx8m_divider_determine_rate") the lcdif controller has
had the ability to set the lcdif_pixel rate which propagates
up the tree and sets the video_pll1 rate automatically.

By setting this value low, it will force the recalculation of
video_pll1 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_pll1 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/imx8mm.dtsi b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
index a3dae114c20e..669fdd2c54e4 100644
--- a/arch/arm64/boot/dts/freescale/imx8mm.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
@@ -1131,7 +1131,7 @@ lcdif: lcdif@...00000 {
 				assigned-clock-parents = <&clk IMX8MM_VIDEO_PLL1_OUT>,
 							 <&clk IMX8MM_SYS_PLL2_1000M>,
 							 <&clk IMX8MM_SYS_PLL1_800M>;
-				assigned-clock-rates = <594000000>, <500000000>, <200000000>;
+				assigned-clock-rates = <24000000>, <500000000>, <200000000>;
 				interrupts = <GIC_SPI 5 IRQ_TYPE_LEVEL_HIGH>;
 				power-domains = <&disp_blk_ctrl IMX8MM_DISPBLK_PD_LCDIF>;
 				status = "disabled";
-- 
2.40.1