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

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Message-ID: <56f1239c-2ca6-488c-9894-8f876a3aecab@kontron.de>
Date:   Thu, 30 Nov 2023 16:46:50 +0100
From:   Frieder Schrempf <frieder.schrempf@...tron.de>
To:     Adam Ford <aford173@...il.com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     aford@...conembeded.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: Re: [PATCH 3/3] arm64: dts: imx8mm: Slow default video_pll1 clock
 rate

On 28.11.23 05:54, 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 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";

Thanks for the cleanup!

Reviewed-by: Frieder Schrempf <frieder.schrempf@...tron.de>
Tested-by: Frieder Schrempf <frieder.schrempf@...tron.de> # Kontron BL
i.MX8MM