On 7/7/2011 6:41 PM, Colin Cross wrote:
On Thu, Jul 7, 2011 at 6:35 PM, Santosh Shilimkar
<santosh.shilim...@ti.com> wrote:
On 7/7/2011 8:50 AM, Lorenzo Pieralisi wrote:
From: Colin Cross<ccr...@android.com>
When the cpu is powered down in a low power mode, the gic cpu
interface may be reset, and when the cpu complex is powered
down, the gic distributor may also be reset.
This patch uses CPU_PM_ENTER and CPU_PM_EXIT notifiers to save
and restore the gic cpu interface registers, and the
CPU_COMPLEX_PM_ENTER and CPU_COMPLEX_PM_EXIT notifiers to save
and restore the gic distributor registers.
Signed-off-by: Colin Cross<ccr...@android.com>
---
arch/arm/common/gic.c | 212
+++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 212 insertions(+), 0 deletions(-)
diff --git a/arch/arm/common/gic.c b/arch/arm/common/gic.c
index 4ddd0a6..8d62e07 100644
--- a/arch/arm/common/gic.c
+++ b/arch/arm/common/gic.c
[...]
+
+static int gic_notifier(struct notifier_block *self, unsigned long cmd,
void *v)
+{
+ int i;
+
+ for (i = 0; i< MAX_GIC_NR; i++) {
+ switch (cmd) {
+ case CPU_PM_ENTER:
+ gic_cpu_save(i);
+ break;
+ case CPU_PM_ENTER_FAILED:
+ case CPU_PM_EXIT:
+ gic_cpu_restore(i);
+ break;
+ case CPU_COMPLEX_PM_ENTER:
+ gic_dist_save(i);
+ break;
+ case CPU_COMPLEX_PM_ENTER_FAILED:
+ case CPU_COMPLEX_PM_EXIT:
+ gic_dist_restore(i);
+ break;
+ }
+ }
+
+ return NOTIFY_OK;
+}
Just to put forth OMAP requirements for GIC and see how much
we can leverage these for OMAP.
OMAP support GP(general) and HS(secure) devices and implements
the trustzone on these devices. on Secure devices the GIC save
and restore is completely done by secure ROM code. There are
API's for save and restore is automatic on CPU reset based
on the last CPU cluster state.
On GP devices too, very few GIC registers needs to be saved
in a pre-defined memory/register layout and restore is again
done by boot-ROM code.
OMAP need to enable/disable distributor and CPU interfaces
based on CPU power states and that is something can be useful.
Would be good if there is a provision to over-write the gic
save/restore function using function pointers so that OMAP
PM code can use the notifiers.
Any more thoughts how we can handle this? We would like to
use common ARM code as much as possible.
Is it strictly necessary to use the custom OMAP save and restore?
Yes. On secure devices there is no choice.
Anything that was modified by the kernel is obviously writable, and
could be saved and restored using the common code. Anything that can
only be modified by TrustZone already has to be restored by the custom
OMAP code. There aren't many registers in the GIC, so it shouldn't be
much of a performance difference.
In that case we will end up doing things two time un-necessary and
that's not useful at all. You need to save all those extra cycles
to have less latency on C-states. And otherside you can't skip the
secure API save otherwise the boot-ROM code will end up re-initializing
the GIC and all secure interrupt state will be lost.
From above code, today we use need dist/cpu interface disable/enable
functions.
Regards
Santosh
Regards
Santosh
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