iMX8QM/QXP Reference Patch to Map Bridge Chip to Display without EDID

[#1]

In defaut Linux BSP, NXP implemented LVDS to HDMI(it6263) and MIPI-DSI to HDMI(adv7535) bridge chip drivers. And these drivers need read the EDID from display, then apply the timing parameters to DRM driver.

But for the use case that bridge chip -> Serializer -> Deserializer -> LCD Panel use case, there is no EDID.

The attached are reference patches for such use case, it combined the bridge chip to panel directly, and no EDID is needed.

The patches are tested on iMX8QXP MEK with bridge chip + panel mode, both of them can see the fb0 device under /sys/class/graphics/ folder, also can see card under  /sys/class/drm/. Display works fine with DTS selected 720P panel mode.

[2020-06-24]: Add patches for L4.14.98 kernel:

Android_Auto_P9.0.0_GA2.1.0_Kernel_No_EDID_IT6263.patch

L4.14.98-iMX8QXP-MEK-ADV7535-MIPI-DSI-to-HDMI-bridge-chip-com.patch

[alvaroga91]

Sorry to bring this topic back after one year but after navigating through the available source in the BSP, I couldn't find the supported maximum resolution of this through a single channel LVDS. We are looking to have 2xHDMI with iMX8QM/QP and we were looking into the IT6263 but not sure if I can trust the IC datasheet to be able to support 2x Full HD with 2xSingle Channel LVDS. 

I see that the test was done 720p so that would confirm my suspicions but not sure if you tested 1080p as well. 

I also see that you are using split-mode for this with dual-channel? https://coral.googlesource.com/linux-imx/+/refs/heads/alpha/arch/arm64/boot/dts/freescale/fsl-imx8qm... 

Thanks

[qiang_li-mpu_se]

The standard 1080P60 is OK for LVDS single channel mode, iMX8QM can support up to 150MHz pixel clock for single LVDS port, for standard 1080P60 display, it is 148.5MHz. 

[smarter]

HI  Li Qiang，

     how I need to modify  the vehicle_rpmsg_m4 node  if I use the attached patch? thank you.

[smarter]

Hi  Li Qiang，

    Thank you. My board platform is imx8qm .  I try it ,It works well on car2 config, it not work on car config. panel in vehicle_rpmsg_m4 node can not  find  proper crtc node  like  crtc-1, how I resolve this issue?

[qiang_li-mpu_se]

For Android Auto, you can reference to "Android_Auto_P9.0.0_GA2.1.0_Kernel_No_EDID_IT6263.patch", and for iMX8QM car, the dts file is "arch/arm64/boot/dts/freescale/fsl-imx8qm-mek-car.dts"