[PATCH] imx-drm: imx-hdmi: fix hdmi hotplug detection initial state

[Tim Harvey]

On Mon, Jun 9, 2014 at 7:29 AM, Fabio Estevam <festevam at gmail.com> wrote:
> On Mon, Jun 9, 2014 at 11:06 AM, Russell King - ARM Linux
> <linux at arm.linux.org.uk> wrote:
>
>> Please check the status in /sys/class/drm/card0-HDMI-A-1/status.  This
>> should report the current state of the hotplug detection.
>
> /sys/class/drm/card0-HDMI-A-1/status returns the correct state for
> HDMI cable connection.
>
>> Remember that this code detects off the HPD signal - if the HPD signal
>> has not been correctly wired up, this patch is not going to help (really
>> it comes down to a hardware fault, which I'm not trying to solve with
>> this patch.)
>>
>> What I'm trying to resolve with this patch is that the state detected
>> on properly wired up systems corresponds with the real initial state of
>> the interface at initialisation time.
>>
>> The problem with the current code is that we start off assuming that the
>> interface is disconnected, and we rely on an interrupt arriving to change
>> that state.  If for whatever reason that interrupt does not arrive, then,
>> even if the HPD signal is active, we continue believing that the interface
>> is not connected.
>>
>> I seem to remember discussion in the past that the HPD signal is not
>> wired up on SabreSD.  Really, this needs to be a DT flag to indicate
>
> It is sabrelite board that does not have HPD signal not wired up.
>
> sabresd does have HPD signal connected.
>
> The HDMI undetected issue I am seeing on sabresd seems to be related
> to the simultaneous usage of HDMI and LVDS.
>
> If I remove the ldb node from the imx6qdl-sabresd.dtsi, then the HDMI
> cable is correctly detected and HDMI is shown right after boot.

Fabio,

I'm following along with this thread as I see the same thing you do on
our Ventana boards that support both LVDS and HDMI: without
hot-plugging the HDMI connector I get not HDMI out simply by having
the LVDS node populated.

I am curious however how you are getting simultaneous display on both
LVDS and HDMI on a SabreSD board as the standard resistor loading
would make the EDID's of both conflict (which causes EDID read
failures) - perhaps you are using an LVDS display with no EDID or
perhaps you have modified the resistor loading on a SabreSD to move
them to different i2cs? Or is there some kernel param/config I don't
see to tell the imx_hdmi driver to ignore EDID and force in a mode?

Regards,

Tim