i.MX6 doesn't recognize MIPI clock from ISL79987

[jpuckett]

I'm attempting to interface an Intersil video decoder eval board with a i.MX6Q sabreauto board using the MIPI CSI2 interface.  The i.MX6's MIPI controller always reports that it is unable to detect a DDR clock coming from the decoder in the MIPI_CSI_PHY_STATE register.

Sabreauto board info:

MCIMX6xAICPU2

SCH-27925 REV F3

700-27925 REV B.

Intersil board info:

ISL79985.87 EVB

It is dated SEP/19/2016 and labelled rev 1.1

The ISL79987 decoder supports up to four simultaneous composite video feeds sent to an external processor using a one or two lane MIPI bus.  We only plan on using two of the video inputs but the decoder driver currently configures the decoder to be in four channel mode.

We made an interface board to connect the two boards using a flex cable (schematic attached).

I'm building our kernel using the FSL community BSP but am using an external kernel source tree since we anticipate some prolonged kernel development.

The kernel version is 4.1.43 and was retrieved from git://github.com/Freescale/linux-fslc.

I got the ISL79987 driver and associated kernel changes from this post:

https://community.nxp.com/docs/DOC-158531

I used the patches in the L4.1.15_ISL7998x_Surroundview_Patch_20161122.zip file attached in that post.

Our kernel source differed from the one used to create the patches so I migrated the code changes manually.

The code builds, boots and correctly discovers the decoder over the I2C bus.

I added a number of test prints to mxc_mipi_csi2.c in the kernel (including a MIPI register dump) so at bootup I see this:

...

udevd[195]: starting eudev-3.2

Galcore version 5.0.11.41671

mipi_csi2_enable() - ret1 = 0, ret2 = 0

isl7998x_hardware_init() - after mipi_csi2_enable()

MIPI_CSI_VERSION = 0x3130302a.

MIPI_CSI_N_LANES = 0x3.

MIPI_CSI_PHY_SHUTDOWNZ = 0x0.

MIPI_CSI_DPHY_RSTZ = 0x0.

MIPI_CSI_CSI2_RESETN = 0x0.

MIPI_CSI_PHY_STATE = 0x200.

MIPI_CSI_DATA_IDS_1 = 0x0.

MIPI_CSI_DATA_IDS_2 = 0x0.

MIPI_CSI_ERR1 = 0x0.

MIPI_CSI_ERR2 = 0x0.

MIPI_CSI_MASK1 = 0x0.

MIPI_CSI_MASK2 = 0x0.

MIPI_CSI_PHY_TST_CTRL0 = 0x0.

MIPI_CSI_PHY_TST_CTRL1 = 0xc00.

mxc_mipi_csi2 21dc000.mipi_csi: mipi_csi2_reset: mipi_lane_bps = 432 Mbps

mxc_mipi_csi2 21dc000.mipi_csi: mipi_csi2_reset: value = 0xc.

isl7998x_hardware_init() - after reg write

MIPI_CSI_VERSION = 0x3130302a.

MIPI_CSI_N_LANES = 0x1.

MIPI_CSI_PHY_SHUTDOWNZ = 0x1.

MIPI_CSI_DPHY_RSTZ = 0x1.

MIPI_CSI_CSI2_RESETN = 0x1.

MIPI_CSI_PHY_STATE = 0x0.

MIPI_CSI_DATA_IDS_1 = 0x0.

MIPI_CSI_DATA_IDS_2 = 0x0.

MIPI_CSI_ERR1 = 0x0.

MIPI_CSI_ERR2 = 0x0.

MIPI_CSI_MASK1 = 0x0.

MIPI_CSI_MASK2 = 0x0.

MIPI_CSI_PHY_TST_CTRL0 = 0x0.

MIPI_CSI_PHY_TST_CTRL1 = 0xc0c.

isl7998x_hardware_init() - after wait for sensor ready

MIPI_CSI_VERSION = 0x3130302a.

MIPI_CSI_N_LANES = 0x1.

MIPI_CSI_PHY_SHUTDOWNZ = 0x1.

MIPI_CSI_DPHY_RSTZ = 0x1.

MIPI_CSI_CSI2_RESETN = 0x1.

MIPI_CSI_PHY_STATE = 0x0.

MIPI_CSI_DATA_IDS_1 = 0x0.

MIPI_CSI_DATA_IDS_2 = 0x0.

MIPI_CSI_ERR1 = 0x0.

MIPI_CSI_ERR2 = 0x0.

MIPI_CSI_MASK1 = 0x0.

MIPI_CSI_MASK2 = 0x0.

MIPI_CSI_PHY_TST_CTRL0 = 0x0.

MIPI_CSI_PHY_TST_CTRL1 = 0xc0c.

mipi csi2 can not receive sensor clk! MIPI_CSI_PHY_STATE = 0x0.

...

The value of the MIPI_CSI_PHY_STATE register has varied throughout this process and these are the values I have observed:

0x0

0x200

0x630

All of these values indicate that the MIPI controller is not detecting the clock from the decoder.

The ISL79987 manual has a table defining the clock speed for various video channel/lane configurations:

1 channel, 1 lane = 108MHz

2 channels, 1 lane = 216MHz

2 channels, 2 lanes = 108MHz

4 channels, 1 lane = 432MHz

4 channels, 2 lanes = 216MHz

I have confirmed with a scope that clocks with these rates are appearing on the clock lane and have traced them to the connector on our interface board that plugs into the MIPI connector (J7) on the sabreauto board.

The mipi_csi2_reset() function in mxc_mipi_csi2.c was modified to vary the D-PHY clock value written based on a passed in bps value.  (See attached)

The isl7998x_hardware_init() function passes this value like this:

/* Only reset MIPI CSI2 HW at sensor initialize */

/* 13.5MHz pixel clock (720*480@30fps) * 16 bits per pixel (YUV422) = 216Mbps mipi data rate for each camera */

mipi_csi2_reset(mipi_csi2_info, (216 * SENSOR_NUM) / (lanes + 1));

SENSOR_NUM is defined as 4 and lanes can be 0 or 1.

The result of this calculation is double the expected MIPI clock from the table in the ISL79987 manual.

The IOMUXC_GPR1 register is configured to correctly select the MIPI interface on the CSI lines using this code in mach-imx6q.c:

gpr = syscon_regmap_lookup_by_compatible("fsl,imx6q-iomuxc-gpr");

if (!IS_ERR(gpr)) {

if (of_machine_is_compatible("fsl,imx6q-sabresd") ||

of_machine_is_compatible("fsl,imx6q-sabreauto"))

regmap_update_bits(gpr, IOMUXC_GPR1, 3 << 19, 0 << 19);

else if (of_machine_is_compatible("fsl,imx6dl-sabresd") ||

 of_machine_is_compatible("fsl,imx6dl-sabreauto"))

regmap_update_bits(gpr, IOMUXC_GPR13, 0x3F, 0x1C);

} else {

pr_err("%s(): failed to find fsl,imx6q-iomux-gpr regmap\n",

       __func__);

}

I have attached the modified kernel code I'm currently using and associated schematics,

Unfortunately I am unable to attach any of the ISL79987 documentation at this time.

[jpuckett]

I retrieved the 4.1.15 kernel source using this git command:

git clone -b imx_4.1.15_2.0.0_ga git://git.freescale.com/imx/linux-imx.git imx_4.1.15_2.0.0_ga

Is this the expected kernel version?

I applied the patches in L4.1.15_ISL7998x_Surroundview_Patch_20161122.zip from the referenced post directly to that source tree.

I had to manually make a couple more changes since I'm building for the sabreauto not the sabresd board.

These changes added the necessary items to the imx6q-sabreauto.dts and imx6qdl-sabreauto.dtsi files to run the ISL79987 driver at startup, add the capture devices and define the MIPI channels.

I also changed mach-imx6q.c so the IOMUXC_GPR1 register correctly enables the MIPI interfaces.

These changes can be seen in the files I attached in the "ISL79987 changed files.zip" file.

With version 4.1.15 I get nearly the same results when the kernel boots:

...

mxc_mipi_csi2 21dc000.mipi_csi: mipi_csi2_reset: mipi_lane_bps = 432 Mbps
mxc_mipi_csi2 21dc000.mipi_csi: mipi_csi2_reset: value = 0xc.
mipi csi2 can not receive sensor clk! MIPI_CSI_PHY_STATE = 0x30.
...

The value in MIPI_CSI_PHY_STATE continues to indicate that the MIPI clock is not detected.

[jpuckett · Accepted solution]

This turned out to be an issue with our interface board.

It was designed using a pinout from the ISL79987 eval guide which is incorrect.

The eval guide defines pins one and two as follows:

1 - MIPI-CLK_N

2 - MIPI-CLK_P

The schematic for the ISL79985.87 EVB shows them swapped:

1 - CSI_CLK0P

2 - CSI_CLK0N

We have since acquired a Wandboard which accepts a direct connection from the ISL79985.87 EVB and continued prototyping with it.

[weidong_sun]

Hello James,

     We released 2 kernel versions of linux BSP : L 4.1.15 &  L4.9.11_1.0.0 , Didn't release L4.1.43.  So please using L 4.1.15 BSP to test surround view application.

Have a great day,
TIC  Weidong Sun

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------