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SubjectRe: [PATCH 06/17] arm64: arch_timer: Get rid of erratum_workaround_set_sne
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On 20/03/17 14:06, Mark Rutland wrote:
> On Mon, Mar 06, 2017 at 11:26:11AM +0000, Marc Zyngier wrote:
>> Let's move the handling of workarounds affecting set_next_event
>> to the affected function, instead of overwriding the pointers
>
> Nit: overriding
>
>> as an afterthough. Yes, this is an extra indirection on the
>> erratum handling path, but the HW is busted anyway.
>
> [...]
>
>> +#define erratum_set_next_event_tval_virt(...) ({BUG_ON(1); 0;})
>> +#define erratum_set_next_event_tval_phys(...) ({BUG_ON(1); 0;})
>
> Nit: BUG()
>
> [...]
>
>> {
>> + if (needs_unstable_timer_counter_workaround())
>> + return erratum_set_next_event_tval_virt(evt, clk);
>> +
>> set_next_event(ARCH_TIMER_VIRT_ACCESS, evt, clk);
>> return 0;
>> }
>> @@ -487,6 +490,9 @@ static int arch_timer_set_next_event_virt(unsigned long evt,
>> static int arch_timer_set_next_event_phys(unsigned long evt,
>> struct clock_event_device *clk)
>> {
>> + if (needs_unstable_timer_counter_workaround())
>> + return erratum_set_next_event_tval_phys(evt, clk);
>> +
>> set_next_event(ARCH_TIMER_PHYS_ACCESS, evt, clk);
>> return 0;
>> }
>
> I take it that the new conditionals are NOPs in the !erratum case, so
> this doesn't adversely affect the usual case.

Indeed, we only get an extra NOP on the normal path. The erratum path
triggers the insertion of a jump targeting the end of the function,
where the workaround gets handled.

Thanks,

M.
--
Jazz is not dead. It just smells funny...

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