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.
Arnd