Re: [PATCH 1/2] Revert "drivers: qcom: rpmh-rsc: Use rcuidle tracepoints for rpmh"

[Maulik Shah]

Hi,

On 8/19/2020 11:34 PM, Stephen Boyd wrote:
> Quoting Maulik Shah (2020-08-19 03:07:49)
> > This change was done based on an test results of unmerged series of
> > adding RSC power domain and using .power_off callback of genpd to
> > invoke rpmh_flush().
> Perhaps:
>
> Commit efde2659b0fe ("drivers: qcom: rpmh-rsc: Use rcuidle tracepoints
> for rpmh") was written to fix a bug seen in an unmerged series that
> implemented a struct generic_pm_domain::power_off() callback calling
> rpmh_flush(). See stack trace below.
Sure i will update in v2.
> >       Call trace:
> >        dump_backtrace+0x0/0x174
> >        show_stack+0x20/0x2c
> >        dump_stack+0xc8/0x124
> >        lockdep_rcu_suspicious+0xe4/0x104
> >        __tcs_buffer_write+0x230/0x2d0
> >        rpmh_rsc_write_ctrl_data+0x210/0x270
> >        rpmh_flush+0x84/0x24c
> >        rpmh_domain_power_off+0x78/0x98
> >        _genpd_power_off+0x40/0xc0
> >        genpd_power_off+0x168/0x208
> >
> > Later the final merged solution is to use CPU PM notification to invoke
> > rpmh_flush() and .power_off callback of genpd is not implemented in the
> > driver.
> I'd also add:
>
> CPU PM notifiers are run with RCU enabled/watching (see cpu_pm_notify()
> and how it calls rcu_irq_enter_irqson() before calling the notifiers).
Sure i will update in v2.
> > Remove this change since RCU will not be idle during CPU PM notifications
> > hence not required to use _rcuidle tracepoint. Using _rcuidle tracepoint
> > prevented rpmh driver to be loadable module as these are not exported
> > symbols.
> >
> > This reverts commit efde2659b0fe835732047357b2902cca14f054d9.
> >
> > Cc: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
> > Cc: John Stultz <john.stultz@xxxxxxxxxx>
> > Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Maulik Shah <mkshah@xxxxxxxxxxxxxx>
> > ---
> Otherwise
>
> Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>

Thanks for the review.

Thanks,
Maulik

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