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

[Luís Mendes]

It is also interesting that I have forced the EDID by specifying the
drm_kms_helper.edid_firmware=edid/ktc_edid.bin in the kernel command line,
and dw_hdmi is still convinced it has no audio, nor HDMI.

[  223.043957] dwhdmi-imx 120000.hdmi: Detected HDMI TX controller
v1.30a with HDCP (DWC HDMI 3D TX PHY)
[  223.047497] hdmi_set_clk_regenerator:521: dwhdmi-imx 120000.hdmi:
hdmi_set_clk_regenerator: fs=48000Hz ftdms=74.250MHz N=6144 cts=74250
[  223.048323] dw_hdmi_irq:2146: dwhdmi-imx 120000.hdmi: EVENT=plugin
[  223.055143] imx-drm display-subsystem: bound 120000.hdmi (ops
dw_hdmi_imx_ops [dw_hdmi_imx])
[  223.057152] [drm] Got external EDID base block and 1 extension from
"edid/ktc_edid.bin" for connector "HDMI-A-1"
[  223.080466] dw_hdmi_setup:1679: dwhdmi-imx 120000.hdmi: Non-CEA
mode used in HDMI
[  223.080501] hdmi_av_composer:1495: dwhdmi-imx 120000.hdmi: final
pixclk = 65000000
[  223.080552] dw_hdmi_phy_power_off:1096: dwhdmi-imx 120000.hdmi: PHY
powered down in 0 iterations
[  223.091885] dw_hdmi_phy_power_on:1133: dwhdmi-imx 120000.hdmi: PHY
PLL locked 1 iterations
[  223.091910] dw_hdmi_phy_power_off:1096: dwhdmi-imx 120000.hdmi: PHY
powered down in 0 iterations
[  223.103160] dw_hdmi_phy_power_on:1133: dwhdmi-imx 120000.hdmi: PHY
PLL locked 1 iterations

-->Here:

[  223.103193] dw_hdmi_setup:1744: dwhdmi-imx 120000.hdmi:
dw_hdmi_setup DVI mode
[  223.140906] Console: switching to colour frame buffer device 128x48
[  223.152326] imx-drm display-subsystem: fb0:  frame buffer device
[  223.185475] [drm] Initialized imx-drm 1.0.0 20120507 for
display-subsystem on minor 1
[  224.226887] [drm] Got external EDID base block and 1 extension from
"edid/ktc_edid.bin" for connector "HDMI-A-1"


On Tue, Nov 7, 2017 at 8:38 AM, Luís Mendes <luis.p.mendes at gmail.com> 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:
> #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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