Re: [PATCH v3 6/6] ACPI: import watchdog info of GTDT into platform device

[Ashwin Chaugule]

On 26 May 2015 at 11:18, Will Deacon <will.deacon@xxxxxxx> wrote:
> On Tue, May 26, 2015 at 04:02:56PM +0100, Ashwin Chaugule wrote:
>> On 26 May 2015 at 08:28, Will Deacon <will.deacon@xxxxxxx> wrote:
>> > On Mon, May 25, 2015 at 11:03:13AM +0100, fu.wei@xxxxxxxxxx wrote:
>> >> From: Fu Wei <fu.wei@xxxxxxxxxx>
>> >>
>> >> Parse SBSA Generic Watchdog Structure in GTDT table of ACPI,
>> >> and create a platform device with that information.
>> >> This platform device can be used by the ARM SBSA Generic
>> >> Watchdog driver.
>> >>
>> >> Tested-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>
>> >> Tested-by: Timur Tabi <timur@xxxxxxxxxxxxxx>
>> >> Signed-off-by: Fu Wei <fu.wei@xxxxxxxxxx>
>> >> ---
>> >>  arch/arm64/kernel/acpi.c | 145 +++++++++++++++++++++++++++++++++++++++++++++++
>> >>  1 file changed, 145 insertions(+)
>> >
>> > Why does this all need to be under arch/arm64? The GTDT really isn't
>> > architecture-specific, so I'd *much* rather it was parsed in the driver code
>> > itself, like we already do for the architected timer. The GIC is an
>> > exception because it's in the MADT, which we need to parse in the arch code
>> > to configure SMP properly.
>>
>> I'm not really against refactoring the code. But the GTDT looks quite
>> specific to ARM..
>>
>> ---8<----
>> 5.2.24 Generic Timer Description Table (GTDT)
>> This section describes the format of the Generic Timer Description
>> Table (GTDT), which provides
>> OSPM with information about a systemâs Generic Timers configuration.
>> The Generic Timer (GT) is
>> a standard timer interface implemented on ARM processor-based systems.
>> The GT hardware
>> specification can be found at Links to ACPI-Related Documents
>> (http://uefi.org/acpi) under the
>> heading ARM Architecture. The GTDT provides OSPM with information
>> about a system's GT
>> interrupt configurations, for both per-processor timers, and platform
>> (memory-mapped) timers.
>> The GT specification defines the following per-processor timers:
>> â Secure privilege level 1 (EL1) timer,
>> â Non-Secure EL1 timer,
>> â Non-Secure privilege level 2 (EL2) timer,
>> â Virtual timer,
>> and the following Platform (memory-mapped) timers.
>> â GT Block
>> â Server Base System Architecture (SBSA) Generic Watchdog
>> ---8<----
>
> Sure, the device it describes may only ever exist on ARM systems, but by
> that logic then we should be moving lots of drivers back under arch/arm[64].

Sure. Not arguing about that. :) You said the GTDT isn't really arch
specific. That was a bit confusing.

>
> The ARM architecture says precisely *nothing* about ACPI, so we should
> try to keep arch/arm64/kernel/acpi.c to a minimum and not shovel all sorts
> of table conversion code in there for random peripherals.
>
> Will
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