Re: [PATCH 3/3] OMAPDSS: HDMI: Cache EDID

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On Thu, 2012-06-28 at 18:43 +0530, Jassi Brar wrote:
> On 28 June 2012 17:33, Andy Green <andy.green@linaro.org> wrote:

> > If Jassi's alright with it we might have a go at implementing this, but can
> > you define a bit more about how we logically tell DSS that we want to, eg,
> > disable HDMI totally?
> >
> A quick reaction of my guts say, we simply enable 5V/HPD_IRQ during
> probe and disable during remove.

The problem with this is a feature of omapdss: we can have multiple
displays for the same output, of which only one can be enabled at the
same time. What this means is that you shouldn't (and in some cases
can't) allocate or enable resources in probe that may be shared, because
then the driver for both displays would try to allocate the same
resource.

Sure, this is not a problem for the HDMI configuration we are using now,
but it's still against the panel model we have. Thus we should allocate
resources only when the panel device is turned on, and release them when
it's disabled.

I do think the model is slightly broken, but that's what we have now.
And I'm also not even sure how it should be fixed...

And also, as I said earlier, if you keep it enabled all the time, it'll
eat power even if the user is never going to use HDMI.

On a desktop I guess the power consumption wouldn't be an issue, but I
do feel a bit uneasy about it on an embedded device.

> HDMI enable/disable via /sysfs/ and HPD (de)assertion, switch only
> HDMI_PHY on/off.
> The user selecting "Autodetect and Configure" option would then equate
> to "(un)loading" of the HDMI driver.

HDMI cannot be currently compiled as a separate module. Although I think
you can detach a device and a driver, achieving the same. Is that what
you meant with unloading?

 Tomi


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