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

[Daniel Lezcano]

On 19/02/2019 10:00, Joseph Lo wrote:
> 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:
>>>>> ÂÂ * refine the timer defines
>>>>> ÂÂ * add ack tag from Jon.
>>>>> v5:
>>>>> ÂÂ * add ack tag from Thierry
>>>>> v4:
>>>>> ÂÂ * merge timer-tegra210.c in previous version into timer-tegra20.c
>>>>> v3:
>>>>> ÂÂ * use timer-of API
>>>>> v2:
>>>>> ÂÂ * 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.

Oh ... right

> 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?

For the moment, I suggest you keep it as it was initially.

A side note, not related to this comment but about the DYNIRQ flag.
Actually it is not needed because the timers are per-cpu.

Thanks

  -- Daniel


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