From: "Yun Wu (Abel)" <wuyun.wu@huawei.com>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: "tglx@linutronix.de" <tglx@linutronix.de>,
"jason@lakedaemon.net" <jason@lakedaemon.net>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 5/6] irqchip: gicv3-its: add support for power down
Date: Tue, 17 Feb 2015 20:27:58 +0800 [thread overview]
Message-ID: <54E333CE.5010800@huawei.com> (raw)
In-Reply-To: <20150217111104.5718d6f1@arm.com>
On 2015/2/17 19:11, Marc Zyngier wrote:
> On Tue, 17 Feb 2015 10:15:15 +0000
> "Yun Wu (Abel)" <wuyun.wu@huawei.com> wrote:
>
>> On 2015/2/17 17:29, Marc Zyngier wrote:
>>
>>> On Sun, 15 Feb 2015 09:32:02 +0000
>>> Yun Wu <wuyun.wu@huawei.com> wrote:
>>>
>>>> It's unsafe to change the configurations of an activated ITS
>>>> directly since this will lead to unpredictable results. This patch
>>>> guarantees a safe quiescent status before initializing an ITS.
>>>
>>> Please change the title of this patch to reflect what it actually
>>> does. Nothing here is about powering down anything.
>>
>> My miss, I will fix this in next version.
>>
>>>
>>>> Signed-off-by: Yun Wu <wuyun.wu@huawei.com>
>>>> ---
>>>> drivers/irqchip/irq-gic-v3-its.c | 32
>>>> ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+)
>>>>
>>>> diff --git a/drivers/irqchip/irq-gic-v3-its.c
>>>> b/drivers/irqchip/irq-gic-v3-its.c index 42c03b2..29eb665 100644
>>>> --- a/drivers/irqchip/irq-gic-v3-its.c
>>>> +++ b/drivers/irqchip/irq-gic-v3-its.c
>>>> @@ -1321,6 +1321,31 @@ static const struct irq_domain_ops
>>>> its_domain_ops = { .deactivate =
>>>> its_irq_domain_deactivate, };
>>>>
>>>> +static int its_check_quiesced(void __iomem *base)
>>>> +{
>>>> + u32 count = 1000000; /* 1s */
>>>> + u32 val;
>>>> +
>>>> + val = readl_relaxed(base + GITS_CTLR);
>>>> + if (val & GITS_CTLR_QUIESCENT)
>>>> + return 0;
>>>> +
>>>> + /* Disable the generation of all interrupts to this ITS */
>>>> + val &= ~GITS_CTLR_ENABLE;
>>>> + writel_relaxed(val, base + GITS_CTLR);
>>>> +
>>>> + /* Poll GITS_CTLR and wait until ITS becomes quiescent */
>>>> + while (count--) {
>>>> + val = readl_relaxed(base + GITS_CTLR);
>>>> + if (val & GITS_CTLR_QUIESCENT)
>>>> + return 0;
>>>> + cpu_relax();
>>>> + udelay(1);
>>>> + }
>>>
>>> You're now introducing a third variant of a 1s timeout loop. Notice
>>> a pattern?
>>>
>>
>> I am not sure I know exactly what you suggest. Do you mean I should
>> code like below to keep the coding style same as the other 2 loops?
>>
>> while (1) {
>> val = readl_relaxed(base + GITS_CTLR);
>> if (val & GITS_CTLR_QUIESCENT)
>> return 0;
>>
>> count--;
>> if (!count)
>> return -EBUSY;
>>
>> cpu_relax();
>> udelay(1);
>> }
>
> That'd be a good start. But given that this is starting to be a common
> construct, it could probably be rewritten as:
>
> static int its_poll_timeout(struct its_node *its, void *data,
> int (*fn)(struct its_node *its,
> void *data))
> {
> while (1) {
> if (!fn(its, data))
> return 0;
>
> ...
> }
> }
>
> and have the call sites to provide the right utility function. We also
> have two similar timeout loops in the main GICv3 driver, so there
> should be room for improvement.
>
> Thoughts?
>
It looks fine to me. I will make some improvement in the next version after
Chinese Spring Festival. :)
Thanks,
Abel
next prev parent reply other threads:[~2015-02-17 12:28 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-15 9:31 [PATCH v2 0/6] enhance configuring an ITS Yun Wu
2015-02-15 9:31 ` [PATCH v2 1/6] irqchip: gicv3-its: zero itt before handling to hardware Yun Wu
2015-02-15 9:31 ` [PATCH v2 2/6] irqchip: gicv3-its: use 64KB page as default granule Yun Wu
2015-02-17 9:46 ` Marc Zyngier
2015-02-15 9:32 ` [PATCH v2 3/6] irqchip: gicv3-its: limit order of DT size to MAX_ORDER Yun Wu
2015-02-17 9:19 ` Marc Zyngier
2015-02-17 10:00 ` Yun Wu (Abel)
2015-02-15 9:32 ` [PATCH v2 4/6] irqchip: gicv3-its: define macros for GITS_CTLR fields Yun Wu
2015-02-15 9:32 ` [PATCH v2 5/6] irqchip: gicv3-its: add support for power down Yun Wu
2015-02-17 9:29 ` Marc Zyngier
2015-02-17 10:15 ` Yun Wu (Abel)
2015-02-17 11:11 ` Marc Zyngier
2015-02-17 12:27 ` Yun Wu (Abel) [this message]
2015-03-04 3:10 ` Yun Wu (Abel)
2015-02-15 9:32 ` [PATCH v2 6/6] irqchip: gicv3: skip ITS init when no ITS available Yun Wu
2015-02-16 10:05 ` Vladimir Murzin
2015-02-16 14:57 ` Yun Wu (Abel)
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