i.MX Processors中的主题 Re: HDMI - pixel alignment issue

HDMI - pixel alignment issue

shajin — Mon, 01 Feb 2021 04:05:56 GMT

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

Re: HDMI - pixel alignment issue

igorpadykov — Mon, 01 Feb 2021 06:44:07 GMT

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-audio/m-p/277073?db=5

Best regards
igor

Re: HDMI - pixel alignment issue

shajin — Tue, 09 Feb 2021 15:08:40 GMT

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.