[PATCH V2 1/6] ARM: tegra: add pending SGI checking API

[Joseph Lo]

On Thu, 2012-12-06 at 06:09 +0800, Stephen Warren wrote:
> On 12/05/2012 03:01 AM, Joseph Lo wrote:
> > The "powered-down" CPU idle mode of Tegra cut off the vdd_cpu rail, it
> > include the power of GIC. That caused the SGI (Software Generated
> > Interrupt) been lost. Because the SGI can't wake up the CPU that in
> > the "powered-down" CPU idle mode. We need to check if there is any
> > pending SGI when go into "powered-down" CPU idle mode. This is important
> > especially when applying the coupled cpuidle framework into "power-down"
> > cpuidle dirver. Because the coupled cpuidle framework may have the
> > chance that misses IPI_SINGLE_FUNC handling sometimes.
> > 
> > For the PPI or SPI, something like the legacy peripheral interrupt. It
> > still can be maintained by Tegra legacy interrupt controller. If there
> > is any pending PPI or SPI when CPU in "powered-down" CPU idle mode. The
> > CPU can be woken up immediately. So we don't need to take care the same
> > situation for PPI or SPI.
> 
> Is this feature something that can/should be added to the core GIC
> driver, rather than something custom in the Tegra code?
> 
This function is SoC specific code not a generic common code even I
modify it to more generic for checking the pending irq (SGI, PPI and
SPI). Different SoC had different design about it. For ex, some SoC only
put CPU core to power saving mode not include GIC, or there is another
irq controller can handle the case when CPU go into power saving mode.
Differenc SoC had different usage here (some need to check all pending
irq, some need to check SGI only and some even no need to consider
this).

> Part of the reason I ask is that I'd like to avoid any more:
> 
> static void __iomem *distbase = IO_ADDRESS(TEGRA_ARM_INT_DIST_BASE);
> 
> since that requires static page tables to be set up, whereas I'd like to
> reduce, as much as possible, the set of pages Tegra maps statically.

I can move this into the function as a temp variable.

Thanks,
Joseph