Fix preempt-rt on AT91

[tglx@linutronix.de (Thomas Gleixner)]

On Tue, 8 Mar 2016, Sebastian Andrzej Siewior wrote:
> I sucked this in. It seems to work. What remains that free_irq() thingy:
> |WARNING: CPU: 0 PID: 0 at kernel/irq/manage.c:1541 __free_irq+0xb4/0x2e0()
> |Trying to free already-free IRQ 16
> |CPU: 0 PID: 0 Comm: swapper Not tainted 4.4.4-rt10+ #219
> |Hardware name: Atmel SAMA5
> |[<c0015bd0>] (unwind_backtrace) from [<c0013604>] (show_stack+0x10/0x14)
> |[<c0013604>] (show_stack) from [<c002b850>] (warn_slowpath_common+0x80/0xac)
> |[<c002b850>] (warn_slowpath_common) from [<c002b8ac>] (warn_slowpath_fmt+0x30/0x40)
> |[<c002b8ac>] (warn_slowpath_fmt) from [<c005adfc>] (__free_irq+0xb4/0x2e0)
> |[<c005adfc>] (__free_irq) from [<c005b0a0>] (free_irq+0x30/0x4c)
> |[<c005b0a0>] (free_irq) from [<c0429034>] (pit_clkevt_shutdown+0x24/0x2c)
> |[<c0429034>] (pit_clkevt_shutdown) from [<c0076430>] (clockevents_switch_state+0x60/0x130)
> |---[ end trace 0000000000000001 ]---
> 
> which is a different problem and was there. The new thing is this:

I think we really need to have this irq_en/disable_action() thingy sooner than
later.

> Is it possible to drop this disable/enable clock on the switch from pit
> to one shot mode?

There was an earlier discussion about the clk stuff. Actually the lock
protecting disable/enable should be made raw, but there was some crap going on
in some of the clk callbacks which made that impossible. We realy should
revisit this.

Thanks,

	tglx