ov5640 sensor parallel interface on IMX6Q

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ov5640 sensor parallel interface on IMX6Q

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vendiracer
Contributor I

Hi,

First I want to show the following diagram:
Screenshot from 2019-11-27 14-08-19.png

We can see that IMX6Q has two IPUs. Each IPU has two inputs: CSI0 and CSI1. It makes four possible inputs:
1) ipu = 0, csi = 0
2) ipu = 0, csi = 1
3) ipu = 1, csi = 0
4) ipu = 1, csi = 1

Looking at device tree include file (provided with linux kernel), we can see the following description of OV5640 sensor connected through MIPI (serial, not parallel) interface:

/* ov5640 camera module */

&i2c2 {
       ov5640_mipi: ov5640_mipi@3c { /* i2c2 driver */
               compatible = "ovti,ov5640_mipi";
               reg = <0x3c>;
               clocks = <&clks 201>;
               clock-names = "csi_mclk";
               DOVDD-supply = <&vgen4_reg>; /* 1.8v */
               AVDD-supply = <&vgen3_reg>;  /* 2.8v, rev C board is VGEN3
                                               rev B board is VGEN5 */
               DVDD-supply = <&vgen2_reg>;  /* 1.5v*/
               pwn-gpios = <&gpio1 19 1>;   /* active low: SD1_CLK */
               rst-gpios = <&gpio1 20 0>;   /* active high: SD1_DAT2 */
               ipu_id = <0>;
               csi_id = <1>;
               vc = <0>;
               mclk = <24000000>;
               mclk_source = <0>;
               status="okay";
       };
};

As we can ipu = 0, and csi = 1 for MIPI camera. OV5640 sensor works fine through MIPI interface. However I don't understand why we use "&i2c2" (i2c bus number 2).

Now I want to connect OV5640 through parallel interface - Parallel 0. "i2cdetect" command sees our sensor on i2c bus number 0, address 0x3c. There is no examples for parallel interface configuration, however there are two OV5640 drivers: "ov5640_mipi" and "ov5640". Also looking at above picture I assume that we need to provide ipu = 0, csi = 0 to work with sensor connected to Parallel 0. And finally it appears that i2c bus number 0 is referenced by "&i2c1". So I change device tree description to the following:

&i2c1 {
       ov5640: ov5640@3c { /* i2c2 driver */
               compatible = "ovti,ov5640";
               reg = <0x3c>;
               clocks = <&clks 201>;
               clock-names = "csi_mclk";
               DOVDD-supply = <&vgen4_reg>; /* 1.8v */
               AVDD-supply = <&vgen3_reg>;  /* 2.8v, rev C board is VGEN3
                                               rev B board is VGEN5 */
               DVDD-supply = <&vgen2_reg>;  /* 1.5v*/
               pwn-gpios = <&gpio1 19 1>;   /* active low: SD1_CLK */
               rst-gpios = <&gpio1 20 0>;   /* active high: SD1_DAT2 */
               ipu_id = <0>;
               csi_id = <0>;
               vc = <0>;
               mclk = <24000000>;
               mclk_source = <0>;
               status="okay";
       };
};

And that does not work. Frame buffer is filled with zeroes.

In this thread:
OV5640 and OV5642 cameras on iMX6
Konstantyn Prokopenko says:

Check IPU configuration in drivers/mxc/ipu3

Make sure you enable proper channels for CSI0 and CSI1 either parallel or MIPI. (ipu_common.c)

Looking at IPU driver (ipu_common.c in /drivers/mxc/ipu3) I didn't find any mention of "parallel" at all. CSI0 and CSI1 channels are referred to by their integer codes "CSI_MEM0" and "CSI_MEM1", however there are another ones: "CSI_MEM2", "CSI_MEM3", "CSI_PRP_ENC_MEM", "CSI_PRP_VF_MEM", "MEM_PRP_VF_MEM", "MEM_VDI_PRP_VF_MEM", "DIRECT_ASYNC0", "DIRECT_ASYNC1" and so on.

There are bunch of another drivers that make direct use of IPU driver. For example ipu_csi_enc.c represents "IPU use case for video capture", it utilizes "CSI_MEM0" and "CSI_MEM1" channels. ipu_prp_enc.c represents "IPU use case for PRP ENC (what is this?)", and utilizes "CSI_PRP_ENC_MEM" channel, and so on.

So do I understand correctly that we need to set ipu = 0, csi = 0 to capture video from Parallel 0 interface? In this case video capturing will de done by ipu_csi_enc.c + ipu_common.c pair on first IPU's CSI_MEM0 channel.

Also there is such thing as IOMUXC_GPR1 register.

Bit 19 controls whether we accept data on IPU0 CSI0 from MIPI (set bit to 1) or from Parallel 0 (set bit to 0)
Bit 20 controls whether we accept data on IPU1 CSI0 from MIPI (set bit to 1) or from Parallel 1 (set bit to 0)

Probably we need to write this register to select parallel source.

Or do we have to configure IPU in another way?

Thank you

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igorpadykov
NXP TechSupport
NXP TechSupport

Hi Igor

for such use case may be useful to check example provided by nxp application team:

iMX6DQ MAX9286 MIPI CSI2 720P camera surround view solution for Linux BSP 

link to nxp offical linux sources and documentation

i.MX Software and Development Tools | NXP 

linux-imx - i.MX Linux kernel 

Best regards
igor
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vendiracer
Contributor I

Hi Igor

This patch adds support for the following configurations:

The 4 cameras can be:

- 1xCSI, 3xMIPI

- 2xCSI, 2xMIPI

- 4xMIPI

CSI stands for Camera Serial Interface, and I know that MIPI also belongs to serial interfaces. However I am interested in Camera Parallel Interface. Or maybe by CSI they mean Camera Parallel Interface?

Thank you

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igorpadykov
NXP TechSupport
NXP TechSupport

Hi Igor

yes CSI is camera parallel interface.

May be useful below presentation

https://community.nxp.com/docs/DOC-100482 

Best regards
igor

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