[PATCH 01/19] ARM: OMAP4: PM: save/restore all DPLL settings in OFF mode

[Bedia, Vaibhav]

On Wed, May 02, 2012 at 17:28:17, Shilimkar, Santosh wrote:
> On Wed, May 2, 2012 at 5:25 PM, Bedia, Vaibhav <vaibhav.bedia at ti.com> wrote:
> > On Wed, May 02, 2012 at 17:17:08, Menon, Nishanth wrote:
> >> On Wed, May 2, 2012 at 6:40 AM, Bedia, Vaibhav <vaibhav.bedia at ti.com> wrote:
> >> >
> >> > On Wed, May 02, 2012 at 16:30:26, Shilimkar, Santosh wrote:
> >> > [...]
> >> >
> >> > > >> How ?
> >> > > >> SRAM is sower memory than DDR so I don't see how it
> >> > > >> will reduce latency.
> >> > > >>
> >> > > >
> >> > > > I am just guessing if that's indeed the case ;)
> >> > > > Haven't done any measurements to really check if that's indeed the
> >> > > > case though.
> >> > > >
> >> > > You don't have to do any real measurements at least on OMAP.
> >> > > OCMC RAM is interfaced over L4 and MPU has to cross two interconnect
> >> > > bridges to reach to SRAM. DDR is more of direct path and much faster.
> >> > >
> >> >
> >> > Hmm, I was under the impression that OCMC RAM was on L3, at least for
> >> > OMAP4.
> >> > Maybe there's a extra low latency path for DDR that I am missing.
> >> have you folks considered the possibility that SRAM may be
> >> reprogrammed by Security code to almost nothing if PA/PPA size needs
> >> to be increased? it would be rather dumb not to support HS devices on
> >> which real products are made, no? rule of thumb has been to avoid
> >> usage of SRAM as it constraints security folks as well (yep, I know
> >> they should share code with all of us etc.. but they have a different
> >> sets of challenges that may deny them such luxury).
> >>
> >
> > Even I would like to avoid the usage of MPUSS SRAM for this very reason.
> > But AFAIK the whole PPA stuff isn't applicable for OCMC RAM (not SRAM inside MPUSS).
> 
> On OMAP, even OCMC RAM can be used by security middle-ware apart from
> reserved SRAM
> for HS/EMU devices.
> That's what Nishant meant.
> 

Oh ok. I wasn't aware of this aspect.

Thanks,
Vaibhav