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

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Message-ID: <a9b6e870-258d-492f-1f1d-5d6ceea24795@nvidia.com>
Date:   Tue, 19 Feb 2019 17:00:55 +0800
From:   Joseph Lo <josephl@...dia.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Thomas Gleixner <tglx@...utronix.de>
CC:     <linux-tegra@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, Thierry Reding <treding@...dia.com>
Subject: Re: [PATCH V6 2/7] clocksource: tegra: add Tegra210 timer support

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@...aro.org>
>>>> Cc: Thomas Gleixner <tglx@...utronix.de>
>>>> Cc: linux-kernel@...r.kernel.org
>>>> Signed-off-by: Joseph Lo <josephl@...dia.com>
>>>> Acked-by: Thierry Reding <treding@...dia.com>
>>>> Acked-by: Jon Hunter <jonathanh@...dia.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.

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