diff mbox

[v3,5/5] irqchip: gicv3-its: support safe initialization

Message ID 1425439098-10708-6-git-send-email-wuyun.wu@huawei.com (mailing list archive)
State New, archived
Headers show

Commit Message

Abel Wu March 4, 2015, 3:18 a.m. UTC 
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(+)

--
1.8.0

Comments

Marc Zyngier March 5, 2015, 12:05 p.m. UTC | #1 
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.
Abel Wu March 6, 2015, 1:34 a.m. UTC | #2 
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
diff mbox

Patch

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)
+{
+	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);
+	}
+}
+
 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);