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HDMI 800x600 support on linux (4.9.88)

Question asked by Gary Pratley on Jul 5, 2019
Latest reply on Jul 5, 2019 by igorpadykov

I've been trying to get a dual display working on the i.MX6QP (EDM1 Fairy). I've a 1024x768 lcd display connected to mxcfb0, and a hdmi display connected to mxcfb1. I've got output on both displays, however I ideally want to configure the hdmi display to 800x600 (svga), but the screen flickers on/off intermittently, anywhere between 0.5/2/3 secs.

Interestingly, we've tried the hdmi output to four different monitors, and they all exhibit this apparent switching on/off (blanking) except for a particular HP display, which appears to work fine.

 

I have added the following to mxc_edid.c,

 

    /* #61: 800x600@60Hz 4:3 */
    [61] = {
        NULL, 60, 800, 600, 25132, 88, 40, 23, 1, 128, 4,
        FB_SYNC_HOR_HIGH_ACT | FB_SYNC_VERT_HIGH_ACT,
        FB_VMODE_NONINTERLACED | FB_VMODE_ASPECT_4_3, 0
    },

 

and to mxc_edid.c:

    /* 800x600@60Hz 4:3 */
    {
        NULL, 60, 800, 600, 25132, 88, 40, 23, 1, 128, 4,
        FB_SYNC_HOR_HIGH_ACT | FB_SYNC_VERT_HIGH_ACT,
        FB_VMODE_NONINTERLACED | FB_VMODE_ASPECT_4_3, FB_MODE_IS_VESA,
    },

and rebuilt the kernel! cat /sys/class/graphics/fb2/modes displays these new modes I added, prefixed with a 'V:'. As an aside, what does the 'V:' indicate?

 

If I configure the hdmi display (mxcfb1 in uEnv.txt) to 1920x1080@60, or 1024x768@60, the display is fine.

Should it be possible to configure the hdmi output for 800x600?

 

The display is connected to a Samsung UHD monitor, which is capable of 800x600 graphics according to the documentation (http://downloadcenter.samsung.com/content/um/201906/20190620124434612/bn46-00904a-eng.pdf ).

 

TIA.

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