HDMI - pixel alignment issue

[shajin]

Hello,

I’m working on a custom platform based out of i.MX6 Sabresd platform and the software running on the platform is Linux Yocto. The Linux kernel version is 4.9.168 and the bootloader is “U-Boot 2020.01". The primary display output is HDMI and the resolution configured is WXGA (1280x800). I’ve ported the smooth transition patch from NXP and got the splash screen running on the target successfully. The transition was smooth and functional. 

I’m observing one issue, On the HDMI monitor the first 4pixel column on the left side of the monitor is not visible. When I enable pixel by pixel on the framebuffer area, I noticed this. The display configuration used in the  bootloader are as follows.

// For HDMI, 1280*800 resolution

#define DISPLAY_WIDTH              1280

#define DISPLAY_HEIGHT             800

#define DISPLAY_BPP                    32

#define DISPLAY_IF_BPP              24  // RGB24 interface

#define DISPLAY_HSYNC_START                220

#define DISPLAY_HSYNC_END                    110

#define DISPLAY_HSYNC_WIDTH              40

#define DISPLAY_VSYNC_START                20

#define DISPLAY_VSYNC_END                    5

#define DISPLAY_VSYNC_WIDTH               5

#define DISPLAY_PIX_CLOCK      74250000

I also tried updating the pixel clock to 74.4 Mhz and changed values corresponds to HBP as well. Unfortunately, Im not successful in getting this issue resolved.

Can you provide your suggestions on this case to address the problem?

Thanks

Shajin

[shajin]

Thanks for the pointers Igor. It helped me to understand more towards the HDMI timing parameters.

As you said, The smooth transition patch was written to support HDMI 720p & 1080p resolutions. It does not have support for 1280x800 wxga resolution. However, when i connected a custom display which supports 1280x800 resolution and with the parameters updated specific to the panel i was able to get the video up and running without any issues. I have created a new entry for wxga in hdmi driver and the board file to get this working.

Thanks for your support.

[igorpadykov]

Hi shajin

issue may be related that 1280x800 is not formally supported as described in

sect.33.4.3 Supported Video Mode  i.MX 6Dual/6Quad Applications Processor Reference Manua

also there may be other implications discussed on

https://community.nxp.com/t5/i-MX-Processors/HDMI-imx6q-sabrelite-Requesting-information-w-r-to-HDMI...

Best regards
igor