VDD2 OPP and DSS

VDD2 OPP and DSS

[Tomi Valkeinen]

Hi Paul and Tero,

Some months ago there were discussions in Nokia about the problem with
VDD2 OPP and DSS fck. The problem was (if I recall right) that the
lowest VDD2 OPP cannot be used if DSS fck is over some certain limit (it
was around 100MHz). If I understood correctly, this was also discussed
with Paul.

Do you remember this (and did I remember it right =)? What is the status
of this?

 Tomi

Re: VDD2 OPP and DSS

[Jarkko Nikula]

On Wed, 2 Mar 2011 08:40:12 +0200
Tomi Valkeinen <tomi.valkeinen@ti.com> wrote:

> Hi Paul and Tero,
> 
> Some months ago there were discussions in Nokia about the problem with
> VDD2 OPP and DSS fck. The problem was (if I recall right) that the
> lowest VDD2 OPP cannot be used if DSS fck is over some certain limit (it
> was around 100MHz). If I understood correctly, this was also discussed
> with Paul.
> 
> Do you remember this (and did I remember it right =)? What is the status
> of this?
> 
At least lower OPP breaks DSS on N900 and Beagle if display is on while
entering into lower OPP.

This made me thinking that should initial round of
"[PATCH 10/13] OMAP3: Add voltage dependency table for VDD1."
use only OMAP3430_VDD_CORE_OPP3_UV for core voltage until there's some
dynamic/DSS voltage domain support in DSS?

http://marc.info/?l=linux-omap&m=129889365901937&w=2

That way, I believe, the DVFS has shorter path to mainline and makes
easier to add driver specific support & hooks. DVFS is not only power
savings but users are interesting about additional performance too.

https://bugs.meego.com/show_bug.cgi?id=13833

-- 
Jarkko