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From: Jassi Brar <jaswinder.singh@linaro.org>
Date: Thu, 28 Jun 2012 12:43:50 +0000
Subject: Re: [PATCH 3/3] OMAPDSS: HDMI: Cache EDID
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To: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: mythripk@ti.com, linux-omap@vger.kernel.org, linux-fbdev@vger.kernel.org, andy.green@linaro.org, n-dechesne@ti.com, patches@linaro.org

On 28 June 2012 16:40, Tomi Valkeinen <tomi.valkeinen@ti.com> wrote:
> On Thu, 2012-06-28 at 16:28 +0530, Jassi Brar wrote:
> >
>> Sorry a correction. Reading detect() won't work. I suggest we keep HPD
>> IRQ enabled for the lifetime of the driver.
>
> Ok, I see. But that's not acceptable. It would require us to keep the
> TPD12S015 always powered and enabled. Even if you're not interested in
> using HDMI at all.
>
 I think we need to differentiate between HDMI PHY enable and HDMI
5V+,HPD enable [1]... currently they are clubbed together in
omap_dss_device.platform_enable.  AFAIK, at least with TPD12S015, they
can be controlled independently and PHY enabling is actually the main
source of power consumption if no display is connected.

By 'lifetime' I mean when the end-user selects some option to the
effect of "Automatically detect and configure display over HDMI" ....
and then we simply enable the HDMI 5V+/HPD,   HDMI-PHY would be
enabled only when we actually detect HPD asserted. If a device doesn't
have a port or the user doesn't have a display, neither would be ever
enabled. I mean we should provide a way to make it platform dependent.


 [1]  Thanks to Andy and his crappy TV, he found clubbing enabling PHY
with 5V+ application comes in the way of detecting cheapo displays
that take ~700ms before asserting HPD i.e, making EDID available. See
how we don't leave it to a HDMI display to take it's own time before
asserting HPD - omapdss_hdmi_display_enable/disable pairs don't care
for that.