topic Re: How to disable MCLK ? in i.MX Processors

How to disable MCLK ?

khang_letruong — Thu, 15 Jun 2023 23:02:48 GMT

Dear Community,

To rule out the impact of MCLK frequency to other high speed interfaces on our custom PCB based on iMX8MP, we have a need to enable/disable the MIPI-CSI2 camera driver in order to enable /disable the MCLK clock:

I re-built the ov5640_mipi_v2.c as loadable kernel module :

diff --git a/arch/arm64/configs/imx_v8_defconfig b/arch/arm64/configs/imx_v8_defconfig index a8a46508482d..a096230294d3 100644 --- a/arch/arm64/configs/imx_v8_defconfig +++ b/arch/arm64/configs/imx_v8_defconfig @@ -528,7 +528,7 @@ CONFIG_VIDEO_MXC_CAPTURE=y CONFIG_VIDEO_MX8_CAPTURE=y CONFIG_VIDEO_MXC_CSI_CAMERA=y CONFIG_MXC_MIPI_CSI=y -CONFIG_MXC_CAMERA_OV5640_MIPI_V2=y +CONFIG_MXC_CAMERA_OV5640_MIPI_V2=m CONFIG_V4L_MEM2MEM_DRIVERS=y CONFIG_SDR_PLATFORM_DRIVERS=y CONFIG_VIDEO_IMX219=m

I saw the in remove() function, clk_disable_unprepare(sensor->sensor_clk) is called. But the 24-MHz MCLK still persists after rmmod.

static int ov5640_remove(struct i2c_client *client) { struct v4l2_subdev *sd = i2c_get_clientdata(client); struct ov5640 *sensor = to_ov5640(client); v4l2_async_unregister_subdev(sd); clk_disable_unprepare(sensor->sensor_clk); ov5640_power_down(sensor, 1); ov5640_regualtor_disable(); return 0; }

I would like to know how to disable it completely during the removing of the module, please?

Thanks in advance and best regards,
Khang

Re: How to disable MCLK ?

joanxie — Mon, 19 Jun 2023 03:51:06 GMT

refer to the schematic

the dts file set this already,

pinctrl_csi_mclk: csi_mclk_grp {
fsl,pins = <
MX8MP_IOMUXC_GPIO1_IO15__CCM_CLKO2 0x50
>;
};

Re: How to disable MCLK ?

khang_letruong — Mon, 19 Jun 2023 06:42:18 GMT

Hi @joanxie ,

Sorry that I did not catch what you meant.Did you mean that MCLK was enabled permanently by the relevant lines in dts file ?

I would like to know if there's any way to disable the MCLK in runtime, please ?

Best Regards,

Khang

Re: How to disable MCLK ?

joanxie — Tue, 20 Jun 2023 07:33:47 GMT

how did you set in the dts file? did you disable this camera in the dts? if yes, did you still measure the mclk 24M from this pin?

Re: How to disable MCLK ?

joanxie — Tue, 20 Jun 2023 07:35:25 GMT

the HW and dts I shared with you, just reminder you checking if you disable it correctly, how did you disable this