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

[Russell King - ARM Linux]

On Tue, Nov 07, 2017 at 08:38:29AM +0000, Luís Mendes wrote:
> 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:

Err - xf86-video-armada gets the EDID from DRM.  DRM gets the EDID from
the dw-hdmi driver.  If the dw-hdmi driver can't get the EDID, then
xf86-video-armada will not have any EDID.

Given the contradictory information, I'm at a loss to explain what you're
seeing - it makes no sense to me.

> #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?

This is the same setup that I use.  If the I2C adapter is not initialised,
then dw-hdmi will defer probing until the I2C adapter is present and ready.

> 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?

*Shrug* no idea, sorry.  I don't understand what the problem is with your
setup, as I say, it makes no sense to me.

-- 
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