Re: [PATCH] arm64: dts: imx8mp: Clarify csis clock frequency

[Alexander Stein <alexander.stein@ew.tq-group.com>]

Hi Laurent,

thanks for the patch.

Am Mittwoch, 14. August 2024, 01:40:10 CEST schrieb Laurent Pinchart:
> The DT nodes for the MIPI CSI-2 receivers (MIPI_CSI) configure the
> CAM1_PIX and CAM2_PIX clocks to 266 MHz through the assigned-clock-rates
> property, and report that frequency in the clock-frequency property. The
> i.MX8MP reference manual and datasheet list 266 MHz as a nominal
> frequency when using both CSI-2 receivers, so all looks normal.
> 
> In reality, the clock is actually set to 250 MHz, as the selected
> parent, IMX8MP_SYS_PLL2_1000M, has a 1/4 output that is selected as the
> closest frequency to 266 MHz. This doesn't break operation of the
> device, but is clearly misleading.
> 
> Clarify the clock configuration by selecting the IMX8MP_SYS_PLL2_250M
> parent, dropping the redundant assigned-clock-rates, and setting
> clock-frequency to 250 MHz. This doesn't cause any functional change.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---
>  arch/arm64/boot/dts/freescale/imx8mp.dtsi | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8mp.dtsi b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> index 603dfe80216f..d9b5c40f6460 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> @@ -1687,7 +1687,7 @@ mipi_csi_0: csi@32e40000 {
>  				compatible = "fsl,imx8mp-mipi-csi2", "fsl,imx8mm-mipi-csi2";
>  				reg = <0x32e40000 0x10000>;
>  				interrupts = <GIC_SPI 17 IRQ_TYPE_LEVEL_HIGH>;
> -				clock-frequency = <266000000>;
> +				clock-frequency = <250000000>;

This doesn't seem to be necessary, no? I can't be read from
IMX8MP_CLK_MEDIA_CAM1_PIX_ROOT. But oh well, that's what we have right now.

Despite that:
Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com>

>  				clocks = <&clk IMX8MP_CLK_MEDIA_APB_ROOT>,
>  					 <&clk IMX8MP_CLK_MEDIA_CAM1_PIX_ROOT>,
>  					 <&clk IMX8MP_CLK_MEDIA_MIPI_PHY1_REF_ROOT>,
> @@ -1695,9 +1695,8 @@ mipi_csi_0: csi@32e40000 {
>  				clock-names = "pclk", "wrap", "phy", "axi";
>  				assigned-clocks = <&clk IMX8MP_CLK_MEDIA_CAM1_PIX>,
>  						  <&clk IMX8MP_CLK_MEDIA_MIPI_PHY1_REF>;
> -				assigned-clock-parents = <&clk IMX8MP_SYS_PLL2_1000M>,
> +				assigned-clock-parents = <&clk IMX8MP_SYS_PLL2_250M>,
>  							 <&clk IMX8MP_CLK_24M>;
> -				assigned-clock-rates = <266000000>;
>  				power-domains = <&media_blk_ctrl IMX8MP_MEDIABLK_PD_MIPI_CSI2_1>;
>  				status = "disabled";
>  
> @@ -1723,7 +1722,7 @@ mipi_csi_1: csi@32e50000 {
>  				compatible = "fsl,imx8mp-mipi-csi2", "fsl,imx8mm-mipi-csi2";
>  				reg = <0x32e50000 0x10000>;
>  				interrupts = <GIC_SPI 80 IRQ_TYPE_LEVEL_HIGH>;
> -				clock-frequency = <266000000>;
> +				clock-frequency = <250000000>;
>  				clocks = <&clk IMX8MP_CLK_MEDIA_APB_ROOT>,
>  					 <&clk IMX8MP_CLK_MEDIA_CAM2_PIX_ROOT>,
>  					 <&clk IMX8MP_CLK_MEDIA_MIPI_PHY1_REF_ROOT>,
> @@ -1731,9 +1730,8 @@ mipi_csi_1: csi@32e50000 {
>  				clock-names = "pclk", "wrap", "phy", "axi";
>  				assigned-clocks = <&clk IMX8MP_CLK_MEDIA_CAM2_PIX>,
>  						  <&clk IMX8MP_CLK_MEDIA_MIPI_PHY1_REF>;
> -				assigned-clock-parents = <&clk IMX8MP_SYS_PLL2_1000M>,
> +				assigned-clock-parents = <&clk IMX8MP_SYS_PLL2_250M>,
>  							 <&clk IMX8MP_CLK_24M>;
> -				assigned-clock-rates = <266000000>;
>  				power-domains = <&media_blk_ctrl IMX8MP_MEDIABLK_PD_MIPI_CSI2_2>;
>  				status = "disabled";
>  
> 
> base-commit: 7c626ce4bae1ac14f60076d00eafe71af30450ba
> 


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