[meta-freescale] No HDMI video on imx6qsabresd with dizzy

Nikolay Dimitrov picmaster at mail.bg
Thu Nov 13 07:17:46 PST 2014

Hi Andreas,

On 11/13/2014 11:29 AM, Andreas Müller wrote:
> On Wed, Nov 12, 2014 at 11:58 PM, Nikolay Dimitrov <picmaster at mail.bg> wrote:
>> Hi guys,
>> I'm trying to use unmodified dizzy build with imx6q sabresd, for
>> testing video playback. U-Boot outputs HDMI image during boot, but in
>> Linux there's no HDMI image (no console, no video playback).
>> The image is "fsl-image-multimedia-full", kernel 3.10.17. The device
>> files /dev/video* and /dev/fb* are available, but gstreamer playback
>> doesn't output any image on the HDMI port (seems to be stuck instead of
>> playing).
>> The kernel cmdline doesn't specify any video settings, which typically
>> is an issue, but when I add the video bootargs:
>> ...video=mxcfb0:dev=hdmi,1024x768M at 60,if=RGB24...
>> The board stops to print any boot messages after "Starting kernel..."
>> and seems to be stuck. Removing the video bootargs allows again to boot
>> normally.
>> I must admit that I'm somewhat puzzled by this behavior, as I already
>> have daizy running with 3.10.17 on a custom board, and the video is
>> working there with almost the same bootargs. Do you guys have any ideas
>> for how to configure imx6q sabresd for HDMI video?
>> Thanks in advance. Regards,
>> Nikolay
>> --
> Had same here.
> I think there are two problems:
> * 3.10.17 EDID decoding works only for monitors with EDID extended
> blocks (patch 0001..)
> * 1024x768 is not a CEA mode. If I read the code of 3.10.17 correct,
> HDMI supports only modes which are found in
> drivers/video/mxc/mxc_edid.c const struct fb_videomode
> mxc_cea_mode[64]. I hacked up working solution (patch 0002..). Note
> that this is just a hack - it might lead to incorrect colour space
> conversion or wrong PixelRepetitionOutput (see mxc_hdmi_setup:
> hdmi->vic is always 0 for my patches).
> These patches were tested with two monitors (1280x1024 / 1650x<I
> forgot>) and seem to work fine.

Thanks for your detailed answer. I remember seeing discussions on the
net about a safe fallback resolution for imx6 hdmi, so that's the only
reason to choose 1024x768.

Also, are you sure that the HDMI code doesn't use the CVT (Common VESA
Table) resolutions? Need to check this. I'll also look a the code
which you pointed me to, and try your patches.

I'm not looking for big or pixel-exact resolutions on HDMI, just some
reasonable resolution so I can test my gstreamer issues there :).


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