HDMI LCD (720x1440) color issue

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HDMI LCD (720x1440) color issue

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Contributor III

We are using I.MX6 Quad core custom board. 

There is a LCD on HDMI with custom resolution of 720x1440.

We are not able to see proper colors on LCD. So, regarding this I have two questions.

Question-1:

To add the custom resolution of 720x1440, we have added mode for this resolution in "mxc_edid.c" file as below.

-----------------------------------------------------------------------------

const struct fb_videomode mxc_cea_mode[64] = {

   NULL, 60, 720, 1440, 13468, 40, 40, 10, 8, 10, 4, 0,
   FB_VMODE_NONINTERLACED, 0,
}

-----------------------------------------------------------------------------

Below the "fbset" command output on board.

-----------------------------------------------------------------------------

mode "720x1440-63"
   # D: 74.250 MHz, H: 91.667 kHz, V: 62.700 Hz
   geometry 720 1440 768 1440 32
   timings 13468 40 40 10 8 10 4
   accel false
   rgba 8/16,8/8,8/0,8/24
endmode

-----------------------------------------------------------------------------

My LCD needs 71.05 MHz of clock frequency. For that, what should be the configuration values in "fb_videomode"?

Question-2: 

Our LCD supports RGB888 pixel format and 24 bits per pixel. But, in DTS "interface_pix_fmt" does not accept RGB888..!!

Is this OK to provide RGB24 instead of RGB888 or What should be the pixel format? 

We are not able to see proper colors.

Below is DTS entry for HDMI.

-----------------------------------------------

mxcfb1: fb@0 {
   compatible = "fsl,mxc_sdc_fb";
   disp_dev = "hdmi";
   interface_pix_fmt = "RGB24";
   mode_str = "720x1440M@60";
   default_bpp = <24>;
   int_clk = <0>;
   late_init = <0>;
   status = "okay";
};

-----------------------------------------------

Thank you very much!

Regards,

Pratik Manvar

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1 Reply

NXP TechSupport
NXP TechSupport

Hi Pratik

hdmi harwdare supports only modes defined in Table 33-3. Video Modes

i.MX6DQ Reference Manual and struct fb_videomode mxc_cea_mode[64],

"mxc_edid.c", no need to add aditional modes.

mxc_edid.c\mxc\fbdev\video\drivers - linux-imx - i.MX Linux kernel 

For workaround with non-cea modes one can check link

https://boundarydevices.com/hdmi-cea-mode/ 

Best regards
igor
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