BBB RevD (and Industrial) IT66122 issues

General Discussion
83

Hello Robert Nelson,

Thank you for your reply.

Unless I’m incorrect, the it66121 DVI patches (merged upstream May 26) are in 7.2-rc5-bone6. And when we tested those patches, the issue persisted.

It seems something else is causing the issue. Will investigate further.

84

The one i’m most interested in, is already in mainline, from Javier:

for a lot of our small displays we want it to force dvi mode: Making sure you're not a bot!

85

Thank you for your reply Robert.

I triple checked everything you said

  • The kernel I’m using has the patches from Javier.
  • Double checked we were using DVI mode by
  • This display is still blank.
  • Nothing suspicious in the kernel logs (linux is happy)
  • I even also installed it on Debian as bbb.io-kernel-7.2-bone instead of our buildroot build

How does someone inspect errors / traffic between the IT66122 and the DVI sink? Everything looks good on the Linux size. I only see a black screen. Everything after tilcdc sends the display data to the IT66122 and the IT66122 driver initializing the device is a black box to me.

I feel like there should be an obvious answer to how debug the HDMI connection but I’m too junior. I am thinking about buying a DDC sniffer. The LLMs tell me the firmware on the LCD controller won’t tell me much, if I can even get into that.

86

I got it working… by swapping out the HDMI DVI adapter on Linux 7.2.

I had done previously swapped out the DVI connector on 6.18, but it didn’t work on 6.18. The DVI connector works on 7.2 though.

EDID doesn’t seem to work on the old adapter. Maybe a pin was broken.

87

We fixed a similar issue.

The ITE framer was throwing a HDMI Audio FIFO overflow, because we used HDMI to DVI. DVI doesn’t support audio. And when given audio it can’t handle the ITE framer will throw interrupts.

Solution was to disable HDMI audio. We needed audio to be exposed to the pins while disabling HDMI audio, so I added this to our device tree.

/ {
	custom_dit: spdif-dit {
		compatible = "linux,spdif-dit";
		#sound-dai-cells = <0>;
	};

	sound {
		simple-audio-card,name = "TI BeagleBone Black - Only I2S No HDMI Audio";
		// TDA and ITE framers only support S32_LE @ 48k
		simple-audio-card,convert-sample-format = "s32_le";
		simple-audio-card,convert-rate = <48000>;

		simple-audio-card,codec {
			sound-dai = <&custom_dit>;
		};
	};
};