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    SubjectRe: [PATCH v2 5/6] irqchip: gicv3-its: add support for power down
    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);
    }

    Thanks,
    Abel



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