Linux/DRA726: HDMI to LVDS Linux driver

Hi Michel,

I have forwarded your question to DSS expert.

Regards,
Yordan

Michel,

Is there a specific point on which you are looking for help?

We have drivers for FPDLink serializer and deserializer in the kernel. These take input from the DSS DPI ports and connect to an LCD display. You can find the drivers in the "drivers/video/serdes" folder. The documentation is in "Documentation/devicetree/bindings/video/fpd3-serdes.txt".

Please go through this and let us know if you have more questions.

regards,
Venkat

Venkat,

Thank you, that is the information I was looking for. There has been a few months since I looked into this and somehow didn't remember which part I had to look for. I will give it a peek to see if there are changes in the newer kernel.

Last I look for the serializer section in kernel 4.4, the device we are using was not supported. In our last product the section was not populated so I put that work aside. If there is still no support I will have to create a driver based on what is already in the kernel.

With the ST Accelerometer I just had to port the driver from kernel 4.9 since it was not supported in kernel 4.4

Michel

Venkat,

I have adapted the driver to support the two devices that we use. The problem I have is that fpd3-serdes.txt doesn't address our use of these devices. So I am not sure exactly how to set the device tree and if my implementation of the driver is entirely correct.

The example has a camera that uses both serializer and deserializer.

In our design we have an external LVDS LCD which is connected to the DS90UH949-Q1. The input is HDMI and LVDS display is connected to the first output (DOUT0+ and DOUT0-). The other output is not connected. DDC pins are not connected, the SPI and I2C lines are connected to the DRA726.

We provide support for video input two ways, with DS90UB948-Q1 where we have an LVDS input. D0 to d3 are connected to csi2_0, the other outputs are not connected. The camera or other video devices to use are not defined yet.

The second way is with 4 analog inputs. It uses a ISL79987 device, our ACTIA partners in Sweden are handling that part with the help of the manufacturer.

Michel

Michel,

How are specifying the display timings? Are hardcoding the EDID in the kernel?

Do you need to do any configuration for the LVDS panel over I2C or is it preconfigured? Do you have any other slaves on the remote end of the FPDLink serializer?

regards,
Venkat

Venkat,

I've been asking similar questions. Normally you'd ask the the info from the LCD device but it looks to me like it would be hardcoded somehow,

I would hope that can be done in the application, I don't want to have to change the kernel for each different display used. It would not be well received if we impose one particular resolution.

The HDMI to LVDS is for an external LVDS monitor which could have different resolutions depending on the customer request. As to how many that is not defined yet. I would assume one but I may be wrong.

The LVDS to video input is for camera most likely. As to how many they connect I will need to ask ACTIA Automotive on this. On most of their boards (power PC and ARM) I think that they usually have 4 cameras.

Michel