[PATCH] arm64: dts: imx8mn: Slow default video_pll clock rate

[PATCH] arm64: dts: imx8mn: Slow default video_pll clock rate

[Adam Ford]

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@gmail.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@32e28000 {
 							 <&clk IMX8MN_SYS_PLL1_800M>;
 				assigned-clock-rates = <266000000>,
 						       <24000000>,
-						       <594000000>,
+						       <24000000>,
 						       <500000000>,
 						       <200000000>;
 				#power-domain-cells = <1>;
-- 
2.43.0


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Re: [PATCH] arm64: dts: imx8mn: Slow default video_pll clock rate

[Shawn Guo]

On Sun, Feb 11, 2024 at 05:15:08PM -0600, Adam Ford wrote:
> 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@gmail.com>

Applied, thanks!


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