Re: [PATCH v1 1/2] arm64: dts: imx8mp: Add CSIS DT nodes

[Adam Ford <aford173@gmail.com>]

On Mon, Apr 17, 2023 at 1:01 AM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Add DT nodes for the two CSI-2 receivers of the i.MX8MP.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---

Laurent,

Sorry to dig up an old thread, but I have a concern about the clock
ratings and nominal mode vs overdrive mode.  I started investigating
the different data sheets amongst the various imx8m[mnp] families to
make the default device trees run at nominal mode while also creating
a separate dtsi file with settings for overdrive so boards who use it
can include them without having to duplicate the clock settings for
everyone who supports overdrive.

>  arch/arm64/boot/dts/freescale/imx8mp.dtsi | 60 +++++++++++++++++++++++
>  1 file changed, 60 insertions(+)
>
> diff --git a/arch/arm64/boot/dts/freescale/imx8mp.dtsi b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> index 2dd60e3252f3..2a374a4c14a2 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> @@ -1239,6 +1239,66 @@ ldb_lvds_ch1: endpoint {
>                                 };
>                         };
>
> +                       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 = <500000000>;
> +                               clocks = <&clk IMX8MP_CLK_MEDIA_APB_ROOT>,
> +                                        <&clk IMX8MP_CLK_MEDIA_CAM1_PIX_ROOT>,
> +                                        <&clk IMX8MP_CLK_MEDIA_MIPI_PHY1_REF_ROOT>,
> +                                        <&clk IMX8MP_CLK_MEDIA_AXI_ROOT>;
> +                               clock-names = "pclk", "wrap", "phy", "axi";
> +                               assigned-clocks = <&clk IMX8MP_CLK_MEDIA_CAM1_PIX>;
> +                               assigned-clock-parents = <&clk IMX8MP_SYS_PLL2_1000M>;
> +                               assigned-clock-rates = <500000000>;

According to Rev 2.1 of the Data sheet (IMX8MPCEC), dated July 2023,
500MHz is listed as single-camera, overdrive mode.  Single-camera,
nominal mode is 400MHz, but there is more...
If configured for dual cameras, both CSI can only support up to
266MHz, but we have partially configured both albeit without the
actual camera sensors connected.

> +                               power-domains = <&media_blk_ctrl IMX8MP_MEDIABLK_PD_MIPI_CSI2_1>;
> +                               status = "disabled";
> +
> +                               ports {
> +                                       #address-cells = <1>;
> +                                       #size-cells = <0>;
> +
> +                                       port@0 {
> +                                               reg = <0>;
> +                                       };
> +
> +                                       port@1 {
> +                                               reg = <1>;
> +                                       };
> +                               };
> +                       };
> +
> +                       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>;
> +                               clocks = <&clk IMX8MP_CLK_MEDIA_APB_ROOT>,
> +                                        <&clk IMX8MP_CLK_MEDIA_CAM2_PIX_ROOT>,
> +                                        <&clk IMX8MP_CLK_MEDIA_MIPI_PHY1_REF_ROOT>,
> +                                        <&clk IMX8MP_CLK_MEDIA_AXI_ROOT>;
> +                               clock-names = "pclk", "wrap", "phy", "axi";
> +                               assigned-clocks = <&clk IMX8MP_CLK_MEDIA_CAM2_PIX>;
> +                               assigned-clock-parents = <&clk IMX8MP_SYS_PLL2_1000M>;
> +                               assigned-clock-rates = <266000000>;

266MHz is correct for dual camera, but in single camera, the second
CSI is capable of 277MHz.

At a minimum, I'd like to fix the overdrive frequency to nominal, but
since we're plumbing in both cameras, I wonder if it would be better
to run both at 266MHz with a note on CSI0 that states it could run at
400 or 500 if the second CSI is disabled and a note on the second CSI
that it could run at 277 when the first one is disabled? What are your
thoughts?


> +                               power-domains = <&media_blk_ctrl IMX8MP_MEDIABLK_PD_MIPI_CSI2_2>;
> +                               status = "disabled";
> +
> +                               ports {
> +                                       #address-cells = <1>;
> +                                       #size-cells = <0>;
> +
> +                                       port@0 {
> +                                               reg = <0>;
> +                                       };
> +
> +                                       port@1 {
> +                                               reg = <1>;
> +                                       };
> +                               };
> +                       };
> +
>                         pcie_phy: pcie-phy@32f00000 {
>                                 compatible = "fsl,imx8mp-pcie-phy";
>                                 reg = <0x32f00000 0x10000>;
> --
> Regards,
>
> Laurent Pinchart
>