Supported resolutions on IMX8MQ via HDMI

[six]

Hi,

we would like to use the IMX8MQ to display a range of resolutions via the HDMI port (e.g. 1920x1200@60), but the driver only seems to offer a limited number of resolutions, and most of the ones we want to support are not among them (from what I understand, the pixel clock can only support a finite number of frequencies?).

My question is: Is this a hardware limitation, or could the driver be expanded to support more resolutions? Furthermore, if it is a hardware limitation, could the DTG (or some other system) be configured in such a way as to increase the blanking times, so that we could "fake" the resolutions we want to support?

Best regards,

Mario

[Rita_Wang]

Hi，

This patch used to do support for a non-default resolution on i.MX 8MQ EVK. Basically the customer needs to change the clocks accordingly to the display requirements，Change the clocks according to the display (non-default

resolution) .

Hope this can do help for you.

Have a nice day

Rita

[six]

Hi Rita,

We're using imx_4.14.98_2.0.0_ga_var01 as the basis for our firmware, where the majority of the patch seems to be already applied. With "changing the clocks" do you mean in the device tree? Are there examples for doing so? Also, changing the frequencies in the device tree would be static, and suited for one specific resolution. Is there a way to change the clocks dynamically?

Best regards,

Mario

[Rita_Wang]

Hi Mario,

Sorry for late reply, I just see your reply today. The patch is for the 4.14.78 version BSP on our i.MX8M EVK board. Yes, you need to modify in device tree. For the clocks changes we can not do it dynamically. You needs to change the clocks accordingly to the your display requirements. You clock you can modify in that patch. You can not directly use that patch, you can refer to it to modify towards your display and board.

Here If you want the non-default resolution work, you also need to modify kernel file:
driver/gpu/drm/imx/hdp/imx-hdp.c and driver/gpu/drm/imx/drm_edid.c
static struct drm_display_mode edid_cea_modes[] = {........}  change to your screen parameters (You can see your screen datasheet).

When you finished the source code modify you need to compile and then download the images to your board.

When you boot up your board you also need to change the boot cmdline in u-boot.

Hope this can do help for you

Best Regards

Rita

[xuboluan]

did i need recompile uboot kenerl and android image

[Rita_Wang]

Yes, if you modify you need to recompile the source code.