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Subject: Re: [PATCH V6 2/7] clocksource: tegra: add Tegra210 timer support
To:     Joseph Lo <josephl@nvidia.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Thomas Gleixner <tglx@linutronix.de>
Cc:     linux-tegra@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, Thierry Reding <treding@nvidia.com>
References: <20190201161654.18315-1-josephl@nvidia.com>
 <20190201161654.18315-3-josephl@nvidia.com>
 <3849a41f-ab36-d7e0-b2ce-1aa5c4e34aec@linaro.org>
 <87731d61-10f6-0842-a90f-0c78ffba9ef7@nvidia.com>
 <d2aff40c-5ec5-ad66-0d69-a76cdd6c0e9c@linaro.org>
 <a9b6e870-258d-492f-1f1d-5d6ceea24795@nvidia.com>
From:   Daniel Lezcano <daniel.lezcano@linaro.org>
Message-ID: <0690a2a2-06e6-62ee-0a5d-dda008fb7fef@linaro.org>
Date:   Tue, 19 Feb 2019 10:33:03 +0100
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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@linaro.org>
>>>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>>>> Cc: linux-kernel@vger.kernel.org
>>>>> Signed-off-by: Joseph Lo <josephl@nvidia.com>
>>>>> Acked-by: Thierry Reding <treding@nvidia.com>
>>>>> Acked-by: Jon Hunter <jonathanh@nvidia.com>
>>>>> ---
>>>>> v6:
>>>>>    * refine the timer defines
>>>>>    * add ack tag from Jon.
>>>>> v5:
>>>>>    * add ack tag from Thierry
>>>>> v4:
>>>>>    * merge timer-tegra210.c in previous version into timer-tegra20.c
>>>>> v3:
>>>>>    * use timer-of API
>>>>> v2:
>>>>>    * add error clean-up code
>>>>> ---
> [snip]
>>>>> +    for_each_possible_cpu(cpu) {
>>>>> +        struct timer_of *cpu_to;
>>>>> +
>>>>> +        cpu_to = per_cpu_ptr(&tegra_to, cpu);
>>>>> +        cpu_to->of_base.base = timer_reg_base +
>>>>> TIMER_BASE_FOR_CPU(cpu);
>>>>> +        cpu_to->of_clk.rate = timer_of_rate(to);
>>>>> +        cpu_to->clkevt.cpumask = cpumask_of(cpu);
>>>>> +
>>>>> +        cpu_to->clkevt.irq =
>>>>> +            irq_of_parse_and_map(np, IRQ_IDX_FOR_CPU(cpu));
>>>>> +        if (!cpu_to->clkevt.irq) {
>>>>> +            pr_err("%s: can't map IRQ for CPU%d\n",
>>>>> +                   __func__, cpu);
>>>>> +            ret = -EINVAL;
>>>>> +            goto out;
>>>>> +        }
>>>>> +
>>>>> +        irq_set_status_flags(cpu_to->clkevt.irq, IRQ_NOAUTOEN);
>>>>> +        ret = request_irq(cpu_to->clkevt.irq, tegra_timer_isr,
>>>>> +                  IRQF_TIMER | IRQF_NOBALANCING,
>>>>> +                  cpu_to->clkevt.name, &cpu_to->clkevt);
>>>>> +        if (ret) {
>>>>> +            pr_err("%s: cannot setup irq %d for CPU%d\n",
>>>>> +                __func__, cpu_to->clkevt.irq, cpu);
>>>>> +            ret = -EINVAL;
>>>>> +            goto out_irq;
>>>>> +        }
>>>>> +    }
>>>>
>>>> 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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