Re: [PATCH V6 2/7] clocksource: tegra: add Tegra210 timer support

[Joseph Lo]

On 2/18/19 5:39 PM, Daniel Lezcano wrote:
> On 18/02/2019 10:01, Joseph Lo wrote:
> > On 2/15/19 11:14 PM, Daniel Lezcano wrote:
> > > On 01/02/2019 17:16, Joseph Lo wrote:
> > > > Add support for the Tegra210 timer that runs at oscillator clock
> > > > (TMR10-TMR13). We need these timers to work as clock event device and to
> > > > replace the ARMv8 architected timer due to it can't survive across the
> > > > power cycle of the CPU core or CPUPORESET signal. So it can't be a
> > > > wake-up
> > > > source when CPU suspends in power down state.
> > > >
> > > > Also convert the original driver to use timer-of API.
> > > >
> > > > Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> > > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > > > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > > > Signed-off-by: Joseph Lo <josephl@xxxxxxxxxx>
> > > > Acked-by: Thierry Reding <treding@xxxxxxxxxx>
> > > > Acked-by: Jon Hunter <jonathanh@xxxxxxxxxx>
> > > > ---
> > > > v6:
> > > >  Â * refine the timer defines
> > > >  Â * add ack tag from Jon.
> > > > v5:
> > > >  Â * add ack tag from Thierry
> > > > v4:
> > > >  Â * merge timer-tegra210.c in previous version into timer-tegra20.c
> > > > v3:
> > > >  Â * use timer-of API
> > > > v2:
> > > >  Â * add error clean-up code
> > > > ---
[snip]
> > > > +ÂÂÂ for_each_possible_cpu(cpu) {
> > > > +ÂÂÂÂÂÂÂ struct timer_of *cpu_to;
> > > > +
> > > > +ÂÂÂÂÂÂÂ cpu_to = per_cpu_ptr(&tegra_to, cpu);
> > > > +ÂÂÂÂÂÂÂ cpu_to->of_base.base = timer_reg_base +
> > > > TIMER_BASE_FOR_CPU(cpu);
> > > > +ÂÂÂÂÂÂÂ cpu_to->of_clk.rate = timer_of_rate(to);
> > > > +ÂÂÂÂÂÂÂ cpu_to->clkevt.cpumask = cpumask_of(cpu);
> > > > +
> > > > +ÂÂÂÂÂÂÂ cpu_to->clkevt.irq =
> > > > +ÂÂÂÂÂÂÂÂÂÂÂ irq_of_parse_and_map(np, IRQ_IDX_FOR_CPU(cpu));
> > > > +ÂÂÂÂÂÂÂ if (!cpu_to->clkevt.irq) {
> > > > +ÂÂÂÂÂÂÂÂÂÂÂ pr_err("%s: can't map IRQ for CPU%d\n",
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ __func__, cpu);
> > > > +ÂÂÂÂÂÂÂÂÂÂÂ ret = -EINVAL;
> > > > +ÂÂÂÂÂÂÂÂÂÂÂ goto out;
> > > > +ÂÂÂÂÂÂÂ }
> > > > +
> > > > +ÂÂÂÂÂÂÂ irq_set_status_flags(cpu_to->clkevt.irq, IRQ_NOAUTOEN);
> > > > +ÂÂÂÂÂÂÂ ret = request_irq(cpu_to->clkevt.irq, tegra_timer_isr,
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ IRQF_TIMER | IRQF_NOBALANCING,
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ cpu_to->clkevt.name, &cpu_to->clkevt);
> > > > +ÂÂÂÂÂÂÂ if (ret) {
> > > > +ÂÂÂÂÂÂÂÂÂÂÂ pr_err("%s: cannot setup irq %d for CPU%d\n",
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ __func__, cpu_to->clkevt.irq, cpu);
> > > > +ÂÂÂÂÂÂÂÂÂÂÂ ret = -EINVAL;
> > > > +ÂÂÂÂÂÂÂÂÂÂÂ goto out_irq;
> > > > +ÂÂÂÂÂÂÂ }
> > > > +ÂÂÂ }
> > >
> > > You should configure the timer in the tegra_timer_setup() function
> > > instead of using this cpu loop.
> >
> > I think I still need to leave 'irq_of_parse_and_map' and 'request_irq'
> > here. Is that ok?
>
> Perhaps you can store the np pointer in the private data structure of
> timer-of and let the timer_of API to retrieve the irq in the cpuhp
> callbacks.
>
> irq_of_parse_and_map will be called by timer-of.
>
> I'm not sure irq_set_status_flags really operates on the irq because it
> is called after request_irq.

I did some experiments today. The 'irq_of_parse_and_map', 'request_irq' 
and 'setup_irq' are not able to run in the atomic section that 
tegra_timer_setup would be triggered in.

So I think I still need to leave the IRQ configuration code here in the 
loop. Should I move others to 'tegra_timer_setup' or just keep as the 
same in this patch?

Thanks,
Joseph