Re: [PATCH 1/3] drm/msm/hdmi: Prevent gpio_free related kernel warnings

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Tue 19 Apr 10:44 PDT 2016, Rob Clark wrote:

>    On Apr 19, 2016 11:50, "Bjorn Andersson" <bjorn.andersson@linaro.org>
>    wrote:
>    >
>    > On Tue 19 Apr 03:56 PDT 2016, Archit Taneja wrote:
>    >
[..]
>    >
>    > The patch in itself looks good, but the bigger picture does not.
>    >
>    > The ddc and hdp should be muxed to the hdmi block, so they should not
>    > operated as gpios.
>    >
>    > The mux seems more of a gpio so it should be made more explicit - i.e.
>    > actually support muxing (if that's needed) rather than just setting hard
>    > coded values.
> 
>    Note that at least on some devices, hpd was unreliable without using a
>    combination of gpio and denounced hpd signal from HDMI block...
> 

Right, I do think it makes sense to keep the detect-gpio.

>    Not sure what sort of MUX it is but it seemed possible (and necessary) to
>    use both at same time..
> 

The "liquid" devices seems to use it, but I haven't managed to figure
out for what.

>    Please be sure to test lots of devices and monitors if you are going to
>    change this ;-)
> 

Scary...


But I do believe that we should stop requesting/freeing the gpios every
time we try to enable/disable them and in the longer run we should drop
the ddc pins, make the hpd an explicit standalone gpiod handle and
figure out what the muxing is all about (and make that standalone as
well).


The patch solves the immediate symptom, but I think we should give it an
overhaul later. If nothing else just to not to carry the downstream
legacy of always gpio_requesting non-gpio pins.

Regards,
Bjorn