Space as well as time. Space is more important factor.
Got it. Presumably you're saving to on-chip SRAM, not DRAM, even for non-secure state.
Generic code should care about both space & time too, but in cases where there's a trade-off between the two there's very clearly a need for SoC specific code (or generic code configurability of some description).
Hence the Save layout is not linear on OMAP4 and restore is handled in by Secure CODE which is fixed for a SOC
Fair enough, but this is an OMAP4 implementation choice, not a general statement about SoCs. (Correct me if I'm wrong.)
Yes. But other SOCs can implement such model as well.
Absolutely. (.. and sorry my mail was imprecise: the comment above referred to non-linear layout, not the fact that there's fixed secure code.)
-Bobby
-----Original Message----- From: Shilimkar, Santosh [mailto:santosh.shilimkar@ti.com] Sent: 18 October 2010 08:09 To: Bobby Batacharia; Jon Callan; linaro-dev@lists.linaro.org Subject: RE: Common ARM context save/restore code
-----Original Message----- From: Bobby Batacharia [mailto:Bobby.Batacharia@arm.com] Sent: Monday, October 18, 2010 12:33 PM To: Shilimkar, Santosh; Jon Callan; linaro-dev@lists.linaro.org Subject: RE: Common ARM context save/restore code
Hi,
Thanks for the response.
The pre-defined locations are needed because not every registers needs
to
be saved. For example in GIC, pending. Clear, Set sets of
register
are pretty much same with inverted logic and can be
easily decoded
without saving all of them but just one type of it. Hence
the Save
layout
Interesting. Why the optimization though - is the intent to
save time
or context space? Every cycle may count, but our
investigations lead
us to believe that the time for any shutdown is dominated by cache (L1) clean times.
Space as well as time. Space is more important factor.
Hence the Save layout is not linear on OMAP4 and restore is handled in by Secure CODE which is fixed for a SOC
Fair enough, but this is an OMAP4 implementation choice,
not a general
statement about SoCs. (Correct me if I'm wrong.)
Yes. But other SOCs can implement such model as well.
Yes... Again I am not saying that you can't have generic
code doing
that.It's doable but it will end up with some SOC specific
execeptions.
Understood.
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