Re: [PATCH v5] drm/i915: pass ELD to HDMI/DP audio driver

[Wu Fengguang <fengguang.wu@intel.com>]

Hi Christopher,

> The log does confirm that the drm_edid_to_eld function is running, and 
> that we're not far from a solution:
> [   21.061417] [drm:drm_edid_to_eld], ELD monitor TX-SR607
> [   21.061421] [drm:drm_edid_to_eld], ELD size 13, SAD count 8

It looks all sane to this point.

> As for where I am getting the EDID dump from, I am getting it from 
> /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-HDMI-A-2/edid, 
> which provides direct virtual access to the EDID response of the 
> connected device.
> 
> I'm completely confident that the device doesn't report too small of a 
> buffer size, and that it's completely compliant with the spec: If you 

Agreed.

> have a Windows virtual machine (or if you're masochistic enough - a real 
> machine) you should download the excellent, free "Monitor Asset Manager" 
> by EnTech Taiwan from http://www.entechtaiwan.com/util/moninfo.shtm. It 
> will let you analyze EDID + ELD + extended timings, etc from an EDID 
> dump, such as the one taken above. It understands every part of EDID.
> 
> I've put together a small archive containing my exact EDID binary dump 
> (taken from the above device path), the FULL dmesg log, as well as 
> EnTech's interpretation of the EDID dump, showing the full list of 
> supported channels, formats, etc.
> 
> I'm guessing there is some tiny bug in your interpretation of how to 
> read ELD, maybe an incorrect 1 byte offset or something like that.
> 
> Here's the pack:
> http://www.pulseforce.com/node/edid_to_eld.zip

Thanks! It's great tool and information!

> If you do a hex analysis of my EDID dump and compare it to what the 
> edid_to_eld function is trying to do, it will probably show what's 
> wrong. I'd love to have a look at that myself but am really busy with a 
> project over here so I can't help out other than to recompile and test 
> as fast as I can.

Would you install the "intel-gpu-tools" package and run its
intel_audio_dump utility? If not shipped with your distribution, the
source code is also available in

git://anongit.freedesktop.org/git/xorg/app/intel-gpu-tools

You'll need to install packages "autotools-dev pkg-config
libpciaccess-dev libdrm-dev libdrm-intel1" in order to build it from
source.

intel_audio_dump will dump the ELD data in the hardware buffer for use
by the audio driver. By verifying if that data is correct, we are able
to analyze whether and how the audio driver goes wrong.

Thanks,
Fengguang