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

[Fabio Estevam]

On Mon, Jun 9, 2014 at 11:33 AM, Shawn Guo <shawn.guo at freescale.com> wrote:
> On Mon, Jun 09, 2014 at 11:29:28AM -0300, Fabio Estevam 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.
>
> This is a known limitation.
>
> http://thread.gmane.org/gmane.linux.ports.arm.kernel/315968/focus=318559

There were versions of linux-next that hdmi and lvds works at the same
time without problems.