[PATCH v3 0/3] ARM: OMAP2+: hwmod: RTC: Add lock and unlock hooks
Paul Walmsley
paul at pwsan.com
Mon Sep 28 09:35:51 PDT 2015
On Thu, 24 Sep 2015, Lokesh Vutla wrote:
> On Thursday 27 August 2015 09:51 AM, Lokesh Vutla wrote:
> > On Thursday 23 July 2015 06:55 PM, Lokesh Vutla wrote:
> >> This series implements lock and unlock functions for RTC and hooks
> >> the same to DRA7 and AMx3xx hwmod.
> >> This is dependent on the patch https://patchwork.kernel.org/patch/6578281/,
> >> which is queued recently by Paul.
> > Gentle ping on this series.
> Do you have any comments on this series?
Looks pretty good. I'm slightly concerned about the latency jitter impact
on -rt kernels for that local_irq_disable() section. Looks like it could
hold off interrupts for ~(50 udelay µs) + 50*((RTC register read time) +
1). But I'm not sure if preempt_enable/disable() is a good alternative
since a bunch of interrupt top halves could conceivably run after the RTC
goes non-busy and result in the RTC not being locked/unlocked.
Is there an RTC IP block register that the code can read, or a safe
sequence that the code can execute, after the RTC lock/unlock operation to
verify that the RTC has successfully been locked or unlocked? If so then
it's probably worth converting the local_irq_disable/enable() to
preempt_disable/enable() and testing that, then retrying the lock/unlock
if it fails.
- Paul
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