iMX8MM MIPI-CSI clock properties setting

[khang_letruong]

Hi All,

I'm integrating an existing driver for Sony IMX296 sensor using the patch from here : https://patchwork.kernel.org/cover/11219369/ 

In the device-tree, I modified the following OV5640 sensor node :

       ov5640_mipi: ov5640_mipi@3c {
                compatible = "ovti,ov5640_mipi";
                reg = <0x3c>;
                status = "okay";
                pinctrl-names = "default";
                pinctrl-0 = <&pinctrl_csi_pwn>, <&pinctrl_csi_rst>;
                clocks = <&clk IMX8MM_CLK_CLKO1>;
                clock-names = "csi_mclk";
                assigned-clocks = <&clk IMX8MM_CLK_CLKO1>;
                assigned-clock-parents = <&clk IMX8MM_CLK_24M>;
                assigned-clock-rates = <24000000>;
                csi_id = <0>;
                pwn-gpios = <&gpio1 7 GPIO_ACTIVE_HIGH>;
                mclk = <24000000>;
                mclk_source = <0>;
                port {
                        ov5640_mipi1_ep: endpoint {
                                remote-endpoint = <&mipi1_sensor_ep>;
                        };
                };
        };

to

       imx296_mipi: imx296_mipi@1a {
                compatible = "sony,imx296_mipi";
                reg = <0x1a>;
                status = "okay";

                pinctrl-names = "default";
                pinctrl-0 = <&pinctrl_csi_pwn>, <&pinctrl_csi_rst>;

                clocks = <&clk IMX8MM_CLK_CSI1_CORE>;
                clock-names = "csi_mclk";
                clock-frequency = <37125000>;
                assigned-clocks = <&clk IMX8MM_CLK_CSI1_CORE>;
                assigned-clock-parents = <&clk IMX8MM_SYS_PLL1_266M>;
                assigned-clock-rates = <37125000>;

                mclk = <37125000>;
                mclk_source = <0>;

                csi_id = <0>;

                rst-gpios = <&gpio1 7 GPIO_ACTIVE_LOW>;

                //vddo-supply = <&reg_camera_board_1p8v>;
                //vdda-supply = <&reg_camera_board_3p3v>;
                //vddd-supply = <&reg_camera_board_1p2v>;

                port {
                        imx296_mipi1_ep: endpoint {
                                remote-endpoint = <&mipi1_sensor_ep>;
                        };
                };
        };

Among the clock properties, I could see that clock-name and clock-frequency are used in the sensor driver's source code. However, it is not quite clear for me the relationship btw clocks, assigned-clocks, assigned-clock-parents, assigned-clock-rates. I would really appreciate if anyone can explain me more, please ?

Also, as the IMX296 sensor requires 37125000 Hz as clock source,  I modified assigned-clock-parents from <&clk IMX8MM_CLK_24M> to <&clk IMX8MM_SYS_PLL1_266M> since from this thread, it is said that "using IMX8MM_CLK_24M [24MHz] as parent seems it is not possible to derive from it 50MHz, assigned-clock-rates = <0>, <50000000>;"

Moreover, I modified clocks and assigned-clocks to IMX8MM_CLK_CSI1_CORE (instead of IMX8MM_CLK_CLKO1 or IMX8MM_CLK_CLKO1_DIV) and I think more logical for CSI interface, do you agree ?

Thanks in advance for your opinion and best regards,

Khang