Re: [PATCH 18/20] clocksource / acpi: Add macro CLOCKSOURCE_ACPI_DECLARE

From: Arnd Bergmann
Date: Wed Jan 22 2014 - 10:48:01 EST

On Wednesday 22 January 2014 15:17:49 Mark Rutland wrote:
> Except for the fact that some timers / clocksources that we already have
> in 32-bit land will likely be reused in 64-bit SoC designs. People will
> want to use the same driver for both 32-bit and 64-bit kernels, and thus
> we need CLOCKSOURCE_OF_DECLARE in 64-bit kernels.
> Those platforms which will have ACPI will likely reuse existing timer IP
> blocks, and will want to make minimal changes to the driver, which will
> likely be using CLOCKSOURCE_OF_DECLARE. We can't change these to
> platform drivers or we can break existing systems because the timers
> will be registered too late.
> I don't see how we can share drivers between 32-bit and 64-bit kernels
> without sharing a common driver model, and I think it makes sense to
> have some uniformity across drivers (i.e. always use
> CLOCKSOURCE_*_DECLARE rather than sometimes using platform drivers).

This still sounds like speculation. I would defer this change until
we actually have a platform that needs it.

The platforms that would reuse a lot of IP blocks are most likely
embedded systems and /not/ server hardware following some strict
specification, so they wouldn't use ACPI.

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