On 2015/2/17 19:11, Marc Zyngier wrote:
> On Tue, 17 Feb 2015 10:15:15 +0000
> "Yun Wu (Abel)" <wuyun...@huawei.com> wrote:
>
>> On 2015/2/17 17:29, Marc Zyngier wrote:
>>
>>> On Sun, 15 Feb 2015 09:32:02 +0000
>>> Yun Wu <wuyun...@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...@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
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