Jonathan McDowell wrote:
> On Wed, Apr 01, 2009 at 07:18:50PM +0100, Chris Jones wrote:
>> I've been doing some work on L3 standby power this afternoon, the
>> primary upshot of which is that there are now hooks in
>> /arch/arm/mach-pxa/balloon3.c for doing things on the way into and out
>> of standby. I cribbed most of the code straight from palmz72.c which
>> seemed to have the right sort of things in it, so if there's a
>> better/more legitimate way to do it, I'm open to ideas.
> 
> Is this code in SVN now? I'm currently concentrating on getting the base
> balloon3 support into mainline kernels, but I'll have a look if that
> ever gets done.

Yes - I folded the changes into balloon3.patch.

>> The same issue arises with the Samosa bus - did parking the bus lines
>> ever get in after the grand TCL kernel hacking session? I can't see it
>> in the code.
> 
> No, this didn't get added so you're not missing anything.

OK. If I was to put in the relevant code, I assume it would go at the
tail end of samosa_suspend_late() and the head end of
samosa_resume_early(), bracketing the power management of the devices on
the bus.

>> Thinking about these things and looking at the code indicates to me
>> that making the relevant control registers in Balloon 3's programmable
>> logic read/write or at least set/reset rather than write-only would
>> make life somewhat easier in the kernel, but could introduce
>> incompatibilities.
> 
> If necessary we can keep local copies of the state and provide accessor
> functions, but being able to query the hardware or at least only frob
> the bits we need to would be much cleaner.

I propose making the registers set/reset, since:
- it uses less logic resource in the hardware than making them readable
- I've already got a VHDL module which does the job
- it makes changing individual bits an atomic operation, leaving no gap
between a read and a writeback which could get interrupted

There are a couple of bits we need to be able to read, as well. Hold
tight for a Balloon 3 register remap.

Chris
-- 
Chris Jones - chris@martin-jones.com
Martin-Jones Technology Ltd, makers of Solidlights
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