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Subject[PATCH v2 5/6] irqchip: gicv3-its: add support for power down
Date
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.

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);
+ }
+
+ return -EBUSY;
+}
+
static int its_probe(struct device_node *node, struct irq_domain *parent)
{
struct resource res;
@@ -1349,6 +1374,13 @@ 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, behaviour unpredictable\n",
+ node->full_name);
+ goto out_unmap;
+ }
+
pr_info("ITS: %s\n", node->full_name);

its = kzalloc(sizeof(*its), GFP_KERNEL);
--
1.8.0



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