Re: [PATCH] Arm: GICv3: Don't access GIC_ICDIPR for interrupts 0..31

[Leif Lindholm <leif.lindholm@linaro.org>]

On Fri, May 19, 2017 at 05:31:36PM +0300, Sergei Temerkhanov wrote:
> On Fri, May 19, 2017 at 1:26 PM, Leif Lindholm <leif.lindholm@linaro.org> wrote:
> > On Fri, May 19, 2017 at 05:37:02AM +0300, Sergei Temerkhanov wrote:
> >> On Thu, May 18, 2017 at 7:08 PM, Ard Biesheuvel
> >> <ard.biesheuvel@linaro.org> wrote:
> >> > On 16 May 2017 at 03:56, Sergey Temerkhanov <s.temerkhanov@gmail.com> wrote:
> >> >> These registers are reserved for PPIs and unimplemented on
> >> >> some architectures
> >> >>
> >> >
> >> >
> >> > What do you mean by 'architectures'?
> >>
> >> GIC core implementations.
> >>
> >> > Could you elaborate on which SoC
> >> > needs this?
> >> At least Cavium ThunderX/OcteonTX need it.
> >>
> >> The GICv3 spec says this on the subject:
> >>
> >> 8.9.12 GICD_IPRIORITYR, Interrupt Priority Registers, n = 0 - 254
> >>
> >> "These registers are always used when affinity routing is not enabled.
> >> When affinity routing is enabled for the Security state of an
> >> interrupt: • GICR_IPRIORITYR is used instead of GICD_IPRIORITYR where
> >> n = 0 to 7 (that is, for SGIs and PPIs). • GICD_IPRIORITYR is RAZ/WI
> >> where n = 0 to 7."
> >
> > Since they are RAZ/WI, why is this change needed?
> 
> B/c for some GICv3 cores accessing these registers result in exceptions

Right, so that's architecturally non-compliant.

At which point, as a workaround for a hardware erratum, I think this
should either be a configurable option (ArmPkg Pcd), or the code
should be modified to use GICR_IPRIORITYR as the text describes (if
applicable).

Regards,

Leif

> Regards,
> Sergey
> 
> >
> > /
> >     Leif
> >
> >> >
> >> >> Signed-off-by: Sergey Temerkhanov <s.temerkhanov@gmail.com>
> >> >> ---
> >> >>  ArmPkg/Drivers/ArmGic/GicV3/ArmGicV3Dxe.c | 2 +-
> >> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >> >>
> >> >> diff --git a/ArmPkg/Drivers/ArmGic/GicV3/ArmGicV3Dxe.c b/ArmPkg/Drivers/ArmGic/GicV3/ArmGicV3Dxe.c
> >> >> index 8af97a9..dc6b896 100644
> >> >> --- a/ArmPkg/Drivers/ArmGic/GicV3/ArmGicV3Dxe.c
> >> >> +++ b/ArmPkg/Drivers/ArmGic/GicV3/ArmGicV3Dxe.c
> >> >> @@ -257,7 +257,7 @@ GicV3DxeInitialize (
> >> >>      MmioOr32 (mGicDistributorBase + ARM_GIC_ICDDCR, ARM_GIC_ICDDCR_ARE);
> >> >>    }
> >> >>
> >> >> -  for (Index = 0; Index < mGicNumInterrupts; Index++) {
> >> >> +  for (Index = 32; Index < mGicNumInterrupts; Index++) {
> >> >>      GicV3DisableInterruptSource (&gHardwareInterruptV3Protocol, Index);
> >> >>
> >> >>      // Set Priority
> >> >> --
> >> >> 2.7.4
> >> >>
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