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SubjectRe: [PATCH v3 5/5] irqchip: gicv3-its: support safe initialization
On 04/03/15 03:18, Yun Wu wrote:
> It's unsafe to change the configurations of an activated ITS directly
> since this will lead to unpredictable results. This patch guarantees
> the ITSes being initialized are quiescent.
>
> Signed-off-by: Yun Wu <wuyun.wu@huawei.com>
> ---
> drivers/irqchip/irq-gic-v3-its.c | 35 +++++++++++++++++++++++++++++++++++
> 1 file changed, 35 insertions(+)
>
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index d13c24e..9e09aa0 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -1320,6 +1320,34 @@ static const struct irq_domain_ops its_domain_ops = {
> .deactivate = its_irq_domain_deactivate,
> };
>
> +static int its_check_quiesced(void __iomem *base)

Another nitpick: Rather than "its_check_quiesced", how about
"its_force_quiescent" instead? Because this does a lot more than just
checking.

> +{
> + 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 (1) {
> + val = readl_relaxed(base + GITS_CTLR);
> + if (val & GITS_CTLR_QUIESCENT)
> + return 0;
> +
> + count--;
> + if (!count)
> + return -EBUSY;
> +
> + cpu_relax();
> + udelay(1);
> + }
> +}
> +

I still dislike this repeated pattern, but I don't have a good solution
so far.

> static int its_probe(struct device_node *node, struct irq_domain *parent)
> {
> struct resource res;
> @@ -1348,6 +1376,13 @@ static int its_probe(struct device_node *node, struct irq_domain *parent)
> goto out_unmap;
> }
>
> + err = its_check_quiesced(its_base);
> + if (err) {
> + pr_warn("%s: failed to quiesce, giving up\n",
> + node->full_name);
> + goto out_unmap;
> + }
> +
> pr_info("ITS: %s\n", node->full_name);
>
> its = kzalloc(sizeof(*its), GFP_KERNEL);
> --
> 1.8.0
>
>
>

Assuming you fix the above nitpick:

Acked-by: Marc Zyngier <marc.zyngier@arm.com>

M.
--
Jazz is not dead. It just smells funny...


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