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SubjectRe: [PATCH v3 5/5] irqchip: gicv3-its: support safe initialization
On 2015/3/5 20:05, Marc Zyngier wrote:

> 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.

Yes, indeed.

>
>> +{
>> + 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.

Me too.

>
>> 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>
>

Thanks,
Abel



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