Re: [Xen-devel] [PATCH v2] arm/gic-v3: Fix ACPI probe fail on GICv4 hardware

[Shanker Donthineni <shankerd@xxxxxxxxxxxxxx>]

On 05/27/2016 10:10 AM, Julien Grall wrote:
> Hello Shanker,
>
> On 27/05/16 16:00, Shanker Donthineni wrote:
>> The current driver ACPI probe fails on hardware which has GICv4
>> version, even though it is fully compatible to GICv3. This patch
>> fixes the issue by registering the same probe function for GICv4
>> hardware.
>>
>> Signed-off-by: Shanker Donthineni <shankerd@xxxxxxxxxxxxxx>
>> ---
>> Changes since v1:
>>     - Edit commit text.
>>     - Fix BUG() in xen/arch/arm/domain.c
>
> Please see my latest comment on the previous version [1].
>
> To go further, the ACPI tables may not represent the actual hardware. It is 
> possible to have ACPI tables describing a GICv2 whilst the real hardware is a 
> GICv3.
>
Yes, it is absolutely valid and UEFI firmware can decide what to be exported to 
OS by changing the version number in ACPI MADT table.

On Qualcomm Technologies QDF2XXX platforms, GIC version set to 4. 

> Xen will use the GICv2 driver and not the GICv3. So the helper will return 
> GIC_V2 (and not GIC_V3).
>

The current xen is supporting both the GICv2 and GICv3 for ACPI based boot.

ACPI_DEVICE_START(agicv3, "GICv3", DEVICE_GIC)
        .class_type = ACPI_MADT_GIC_VERSION_V3,
        .init = gicv3_acpi_preinit,
ACPI_DEVICE_END

ACPI_DEVICE_START(agicv2, "GICv2", DEVICE_GIC)
        .class_type = ACPI_MADT_GIC_VERSION_V2,
        .init = gicv2_acpi_preinit,
ACPI_DEVICE_END

> Regards,
>
> [1] https://www.mail-archive.com/xen-devel@xxxxxxxxxxxxx/msg69273.html
>

-- 
Shanker Donthineni
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux 
Foundation Collaborative Project


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