Re: [Xen-devel] [PATCH v7 1/5] xen/arm: Add support for GIC v3

[Vijay Kilari <vijay.kilari@xxxxxxxxx>]

On Tue, Jul 22, 2014 at 4:25 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Tue, 2014-07-22 at 16:19 +0530, Vijay Kilari wrote:
>> >
>> >> >> + * Additional registers defined in GIC v3.
>> >> >> + * Common GICD registers are defined in gic.h
>> >> >> + */
>> >> >> +
>> >> >> +#define GICD_STATUSR                 (0x010)
>> >> >> [...][
>> >> >> +#define GICV3_GICD_PIDR0             (0x92)
>> >> >
>> >> > What is the distinction between variables with GIC[DR]_ prefixes and
>> >> > those with GICV3_GIC[DR]_ ones?
>> >>
>> >> GICV3 is prefixed for indicating that there are values not the addresses.
>> >> In anycase I will remove GICV3 prefixes and postfix _VAL
>> >
>> > You mean the value used when emulating a read, I think?
>>
>>    Yes, it is used in gicv3 driver for checking presence of re-distributor
>
> In the phsyical h/w? That sounds wrong. 0x92 is just one possible value
> of this register (and the spec says it should be 0x94...). I don't see
> you using this #define in that way anywhere though so perhaps I've
> misunderstood.

I am using 20.0 version. which specifies 0x92 for ARM implementations of GICv3.
May be other vendors can use different value. So it is better propagate hw value
for emulation

 GICD_PIDR0:
 Bits [7:0]. Bits [7:0] of the ARM-defined DevID field. This field is 0x92 in
ARM implementations of a GICv3 or later Distributor.

In any case, GICD_PIDR0 is not used by gicv3 driver. GICD_PIDR2 & GICR_PIDR2 are
 used where check is made on ARCH_REV [7:4]

>
>> and also in vgicv3 for emulating read.
>
> I wonder if we should instead propagate the underlying hardware value?

Yes,we can propagate hardware value.

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