how to configure 1920x1200 resolution on a imx6q

[adc1]

Hi,

I need to use a 1920x1200 resolution on a imx6 board to connect an HDMI projector but I can't find the correct parameters to setup it. I have already found other threads that face this issue, but no one of them shows which parameters to use.

need iMX6 Quad HDMI 1920x1200 support

1920x1200 support on iMX6Q

I'm trying to modify mxc_hdmi.c by adding a specific fb_videomode similar to this

static const struct fb_videomode xga_mode = {

/* 13 1024x768-60 VESA */

NULL, 60, 1024, 768, 15384, 160, 24, 29, 3, 136, 6,

0, FB_VMODE_NONINTERLACED, FB_MODE_IS_VESA

};

could someone tell me how to configure it for 1920x1200 resolution?

thank you for the attention,

regards

Andrea

[adc1]

Hi Gary,

yes, from a x86 pc I can correctly get EDID data. I don't know why on imx6 I get that error.

by the way, I have found a way to let projector hook 1920x1200 resolution: I created another fb_videomode at 30Hz and using it all seems going right. What could be the issue? Why could it not support an higher Hz on imx6?

Regards,

Andrea

[gary_bisson]

Hi Andrea,

Higher frequency means faster clocks, either the kernel can't achieve a clock that is fast enough or the one that is being set doesn't match the timings requirement of your projector.

If you can retrieve the EDID from your x86 machine, we added a feature in our kernel that allows to override the EDID, see example:

linux-imx6/imx6qdl-insp.dtsi at boundary-imx_3.14.52_1.1.0_ga · boundarydevices/linux-imx6 · GitHub

Let me know how it goes.

Regards,

Gary

[adc1]

Hi,

could someone help me? I'm using a 3.14.28 kernel and I tried to add WUXGA resolution defining a specific fb_videomode element in mxc_hdmi.c and adding it in mxc_hdmi_edid_rebuild_modelist function as follows:

     static const struct fb_videomode wuxga_mode = {
          /* 1920x1200 @60, 74.0 kHz hsync */

          NULL, 60, 1920, 1200, 6493, 80, 48, 26, 3, 32, 6,

          FB_SYNC_HOR_HIGH_ACT,

          FB_VMODE_NONINTERLACED, FB_MODE_IS_VESA,

     };

     fb_add_videomode(&wuxga_mode, &hdmi->fbi->modelist);

I have configured the wuxga_mode structure calculating parameters from VESA specification as suggested in that thread. it seems ok, with the modified kernel I found WUXGA resolution in xrandr list but selecting it with xrandr --size 1920x1200 the projector doesn't show video output in a correct way: image go on for a certain time, then it disappears, and so on, flickering. have I to do modify something else in kernel modules? what could be wrong? could imx6 support this resolution?

thank you for the attention,

regards

Andrea

[gary_bisson]

Hi Andrea,

Is the EDID of your device correct? Do you have the allow_noncea variable set in U-Boot?

U-Boot> setenv allow_noncea

U-Boot> savee

When this variable is set, you should be able to see the resolutions your display supports in sysfs:

# cat /sys/class/graphics/fb0/modes

Then you should be able to change the resolution you should be able to use the exact timings provided in the EDID by issuing:

# echo <your_resolution> > /sys/class/graphics/fb0/mode

If you want this resolution to be used at every bootup, the best is to modify the device tree and set the desired resolution.

Regards,

Gary

[adc1]

Hi Gary,

thank you for the reply. my device doesn't support EDID, when called mxc_hdmi_read_edid it returns HDMI_EDID_FAIL.

anyway, it doesn't seem to affect modes list. I can see 1920x1200 resolution in /sys/class/graphics/fb0/modes as I add this fb_videomode as previously described.

The problem is when I select it: certain times video output is temporarily shown at 1920x1200 but most times projector seems to reject this resolution. I assume fb_videomode parameters are correct cause sometimes image is shown, am I wrong?

I also tried to setup this resolution as the default one modifying the device tree but nothing changes.

What could be the problem? What could I check in mxc_hdmi kernel module?

Could be a clock issue?

thank you for the attention,

regards

Andrea

[gary_bisson]

Hi Andrea,

Yes you can check the clocks in the sysfs:

# cat /sys/kernel/debug/clk/clk_summary

But since certain times the video is shown, I suspect more of a timings issue, maybe your projector doesn't support the standard timings but needs some custom ones, which is what the EDID should be able to tell you.

If I were you I'd first try to fix that EDID issue, what happens when you connect this projector to your pc? Can you get the EDID from there?

Regards,

Gary