linux-kernel - Re: [PATCH v2] drivers/clocksource/mediatek: Ack and disable interrupts on shutdown

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Message-ID: <67eed9a2-2b97-be1b-3290-948da662ea65@linaro.org>
Date:   Fri, 2 Apr 2021 16:15:13 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Evan Benn <evanbenn@...il.com>
Cc:     Evan Benn <evanbenn@...omium.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Alexey Klimov <alexey.klimov@...aro.org>,
        Julia Lawall <Julia.Lawall@...6.fr>,
        Yingjoe Chen <yingjoe.chen@...iatek.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        Viresh Kumar <viresh.kumar@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Fabien Parent <fparent@...libre.com>
Subject: Re: [PATCH v2] drivers/clocksource/mediatek: Ack and disable
 interrupts on shutdown


Hi Evan,

On 27/03/2021 02:31, Evan Benn wrote:
> Hi Daniel,
> 
> That is a good point, and I did try that at first and it works fine. I
> uploaded this version because the suspend/resume callbacks were
> undocumented and mostly not used by other clocksource drivers. I
> thought a smaller diff might be preferable.
> I also thought it would be better to shut off the interrupt as soon as
> it is not needed, avoiding any other potential bugs, instead of just
> fixing the one we know about with suspend. I'm not sure how the other
> driver / timer disable flows are intended to work for example
> (shutdown, detach, etc).
> 
> That said I am happy to upload that version if people think it is better.

IMO, it is not in the normal flow to disable/enable the interrupts.

Does this timer belong to an always-on power domain ?



> https://elixir.bootlin.com/linux/latest/source/include/linux/clockchips.h#L120
> 
> 
> On Thu, 25 Mar 2021 at 19:10, Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
>>
>> On 25/03/2021 02:35, Evan Benn wrote:
>>> set_state_shutdown is called during system suspend after interrupts have
>>> been disabled. If the timer has fired in the meantime, there will be
>>> a pending IRQ. So we ack that now and disable the timer. Without this
>>> ARM trusted firmware will abort the suspend due to the pending
>>> interrupt.


>>> Now always disable the IRQ in state transitions, and re-enable in
>>> set_periodic and next_event.
>>
>> Why not put add the suspend/resume callbacks and put there the specific
>> code and let the irq untouched in the normal flow ?
>>
>>> Signed-off-by: Evan Benn <evanbenn@...omium.org>
>>> ---
>>>
>>> Changes in v2:
>>> Remove the patch that splits the drivers into 2 files.
>>>
>>>  drivers/clocksource/timer-mediatek.c | 49 +++++++++++++++++-----------
>>>  1 file changed, 30 insertions(+), 19 deletions(-)
>>>
>>> diff --git a/drivers/clocksource/timer-mediatek.c b/drivers/clocksource/timer-mediatek.c
>>> index 9318edcd8963..fba2f9494d90 100644
>>> --- a/drivers/clocksource/timer-mediatek.c
>>> +++ b/drivers/clocksource/timer-mediatek.c
>>> @@ -132,13 +132,33 @@ static u64 notrace mtk_gpt_read_sched_clock(void)
>>>       return readl_relaxed(gpt_sched_reg);
>>>  }
>>>
>>> +static void mtk_gpt_disable_ack_interrupts(struct timer_of *to, u8 timer)
>>> +{
>>> +     u32 val;
>>> +
>>> +     /* Disable interrupts */
>>> +     val = readl(timer_of_base(to) + GPT_IRQ_EN_REG);
>>> +     writel(val & ~GPT_IRQ_ENABLE(timer), timer_of_base(to) +
>>> +            GPT_IRQ_EN_REG);
>>> +
>>> +     /* Ack interrupts */
>>> +     writel(GPT_IRQ_ACK(timer), timer_of_base(to) + GPT_IRQ_ACK_REG);
>>> +}
>>> +
>>>  static void mtk_gpt_clkevt_time_stop(struct timer_of *to, u8 timer)
>>>  {
>>>       u32 val;
>>>
>>> +     /* Disable timer */
>>>       val = readl(timer_of_base(to) + GPT_CTRL_REG(timer));
>>>       writel(val & ~GPT_CTRL_ENABLE, timer_of_base(to) +
>>>              GPT_CTRL_REG(timer));
>>> +
>>> +     /* This may be called with interrupts disabled,
>>> +      * so we need to ack any interrupt that is pending
>>> +      * Or for example ATF will prevent a suspend from completing.
>>> +      */
>>> +     mtk_gpt_disable_ack_interrupts(to, timer);
>>>  }
>>>
>>>  static void mtk_gpt_clkevt_time_setup(struct timer_of *to,
>>> @@ -152,8 +172,10 @@ static void mtk_gpt_clkevt_time_start(struct timer_of *to,
>>>  {
>>>       u32 val;
>>>
>>> -     /* Acknowledge interrupt */
>>> -     writel(GPT_IRQ_ACK(timer), timer_of_base(to) + GPT_IRQ_ACK_REG);
>>> +     /* Enable interrupts */
>>> +     val = readl(timer_of_base(to) + GPT_IRQ_EN_REG);
>>> +     writel(val | GPT_IRQ_ENABLE(timer),
>>> +            timer_of_base(to) + GPT_IRQ_EN_REG);
>>>
>>>       val = readl(timer_of_base(to) + GPT_CTRL_REG(timer));
>>>
>>> @@ -226,21 +248,6 @@ __init mtk_gpt_setup(struct timer_of *to, u8 timer, u8 option)
>>>              timer_of_base(to) + GPT_CTRL_REG(timer));
>>>  }
>>>
>>> -static void mtk_gpt_enable_irq(struct timer_of *to, u8 timer)
>>> -{
>>> -     u32 val;
>>> -
>>> -     /* Disable all interrupts */
>>> -     writel(0x0, timer_of_base(to) + GPT_IRQ_EN_REG);
>>> -
>>> -     /* Acknowledge all spurious pending interrupts */
>>> -     writel(0x3f, timer_of_base(to) + GPT_IRQ_ACK_REG);
>>> -
>>> -     val = readl(timer_of_base(to) + GPT_IRQ_EN_REG);
>>> -     writel(val | GPT_IRQ_ENABLE(timer),
>>> -            timer_of_base(to) + GPT_IRQ_EN_REG);
>>> -}
>>> -
>>>  static struct timer_of to = {
>>>       .flags = TIMER_OF_IRQ | TIMER_OF_BASE | TIMER_OF_CLOCK,
>>>
>>> @@ -292,6 +299,12 @@ static int __init mtk_gpt_init(struct device_node *node)
>>>       if (ret)
>>>               return ret;
>>>
>>> +     /* In case the firmware left the interrupts enabled
>>> +      * disable and ack those now
>>> +      */
>>> +     mtk_gpt_disable_ack_interrupts(&to, TIMER_CLK_SRC);
>>> +     mtk_gpt_disable_ack_interrupts(&to, TIMER_CLK_EVT);
>>> +
>>>       /* Configure clock source */
>>>       mtk_gpt_setup(&to, TIMER_CLK_SRC, GPT_CTRL_OP_FREERUN);
>>>       clocksource_mmio_init(timer_of_base(&to) + GPT_CNT_REG(TIMER_CLK_SRC),
>>> @@ -305,8 +318,6 @@ static int __init mtk_gpt_init(struct device_node *node)
>>>       clockevents_config_and_register(&to.clkevt, timer_of_rate(&to),
>>>                                       TIMER_SYNC_TICKS, 0xffffffff);
>>>
>>> -     mtk_gpt_enable_irq(&to, TIMER_CLK_EVT);
>>> -
>>>       return 0;
>>>  }
>>>  TIMER_OF_DECLARE(mtk_mt6577, "mediatek,mt6577-timer", mtk_gpt_init);
>>>
>>
>>
>> --
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>>
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