Question regarding HDMI Audio support on i.MX6 with vanilla kernel

[Luís Mendes]

It is interesting that xf86-video-armada is able to get the EDID data, also
if I run get-edid from the command line I get:
#sudo get-edid > tv.edid
This is read-edid version 3.0.2. Prepare for some fun.
Attempting to use i2c interface
No EDID on bus 0
No EDID on bus 2
1 potential busses found: 1
256-byte EDID successfully retrieved from i2c bus 1
Looks like i2c was successful. Have a good day.

parse-edid shows that the read data is from the TV and is correct.

Fabio prepared the DTS files and they look correct too, that is:
imx6qdl-wandboard.dtsi
...
&hdmi {
    ddc-i2c-bus = <&i2c1>;
    status = "okay";
}
...

Could it be that EDID is being read before i2c is initialized? Or a bug in
dw-hdmi?

Anyway wouldn't it make sense to add a kernel parameter has_audio={-1,0,1}?
-1 = auto
0 = force no audio
1 = force audio

Then if the user has a kernel command line like: video=HDMI-A-1:1024x768M at 60
dw_hdmi.has_audio=1, then:
1 - dw_hdmi should accept there is a HDMI connection despite it is unable
to read the EDID, because video=HDMI-A-1
2 - since dw_hdmi.has_audio=1 then audio and HDMI should be enabled.

What do you think? Does it make sense for me do create a patch for this?

On Mon, Nov 6, 2017 at 11:46 PM, Russell King - ARM Linux <
linux at armlinux.org.uk> wrote:

> On Mon, Nov 06, 2017 at 11:33:18PM +0000, Luís Mendes wrote:
> > I've enable dynamic debug in the kernel module and got this log below.
> > Is it my impression or dw_hdmi goes into DVI mode because is unable to
> get
> > edid, which is why I don't get sound?
> > According to the module code in dw_hdmi_connector_get_modes of dw-hdmi.c:
> > hdmi->sink_is_hdmi and hdmi->sink_has_audio is only set when EDID can be
> > read via I2C DDC.
>
> Yep, that'll be it then.  I think you need to solve the EDID reading
> first.  I'd say, check your pinmux settings.
>
> If you're using a normal I2C controller rather than dw-hdmi's built-in
> DDC, then (iirc) you need different pinmux settings - at least on
> imx6q/d/sl that's the case.
>
> --
> RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps
> up
> According to speedtest.net: 8.21Mbps down 510kbps up
>
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