Message-ID: <e8133dc27a2fb1c92b107f1f34a71c20@codeaurora.org>
Date:   Wed, 16 Nov 2016 13:29:57 -0500
From:   Agustin Vega-Frias <agustinv@...eaurora.org>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, rjw@...ysocki.net,
        lenb@...nel.org, tglx@...utronix.de, jason@...edaemon.net,
        marc.zyngier@....com, timur@...eaurora.org, cov@...eaurora.org,
        agross@...eaurora.org, harba@...eaurora.org, jcm@...hat.com,
        msalter@...hat.com, mlangsdo@...hat.com, ahs3@...hat.com,
        astone@...hat.com, graeme.gregory@...aro.org, guohanjun@...wei.com,
        charles.garcia-tobin@....com
Subject: Re: [PATCH V7 1/3] ACPI: Retry IRQ conversion if it failed previously

Hi Lorenzo,

On 2016-11-16 12:18, Lorenzo Pieralisi wrote:
> On Tue, Nov 15, 2016 at 12:43:38PM -0500, Agustin Vega-Frias wrote:
>> Hi Lorenzo,
>> 
>> On 2016-11-15 10:48, Lorenzo Pieralisi wrote:
>> >On Sun, Nov 13, 2016 at 04:59:33PM -0500, Agustin Vega-Frias wrote:
>> >>This allows probe deferral to work properly when a dependent device
>> >>fails to get a valid IRQ because the IRQ domain was not registered
>> >>at the time the resources were added to the platform_device.
>> >>
>> >>Signed-off-by: Agustin Vega-Frias <agustinv@...eaurora.org>
>> >>---
>> >> drivers/acpi/resource.c | 59
>> >>+++++++++++++++++++++++++++++++++++++++++++++++++
>> >> drivers/base/platform.c |  9 +++++++-
>> >> include/linux/acpi.h    |  7 ++++++
>> >> 3 files changed, 74 insertions(+), 1 deletion(-)
>> >>
>> >>diff --git a/drivers/acpi/resource.c b/drivers/acpi/resource.c
>> >>index 56241eb..4beda15 100644
>> >>--- a/drivers/acpi/resource.c
>> >>+++ b/drivers/acpi/resource.c
>> >>@@ -664,3 +664,62 @@ int acpi_dev_filter_resource_type(struct
>> >>acpi_resource *ares,
>> >> 	return (type & types) ? 0 : 1;
>> >> }
>> >> EXPORT_SYMBOL_GPL(acpi_dev_filter_resource_type);
>> >>+
>> >>+struct acpi_irq_get_ctx {
>> >>+	unsigned int index;
>> >>+	struct resource *res;
>> >>+};
>> >>+
>> >>+static acpi_status acpi_irq_get_cb(struct acpi_resource *ares,
>> >>void *context)
>> >>+{
>> >>+	struct acpi_irq_get_ctx *ctx = context;
>> >>+	struct acpi_resource_irq *irq;
>> >>+	struct acpi_resource_extended_irq *ext_irq;
>> >>+
>> >>+	switch (ares->type) {
>> >>+	case ACPI_RESOURCE_TYPE_IRQ:
>> >>+		irq = &ares->data.irq;
>> >>+		if (ctx->index < irq->interrupt_count) {
>> >>+			acpi_dev_resource_interrupt(ares, ctx->index, ctx->res);
>> >>+			return AE_CTRL_TERMINATE;
>> >>+		}
>> >>+		ctx->index -= irq->interrupt_count;
>> >
>> >I do not understand this code, mind explaining what it is meant to do ?
>> >
>> >In particular I do not understand the logic behind the index decrement,
>> >I think I am missing something here.
>> >
>> 
>> ACPI IRQ resources can be encoded into two types of structures:
>> 
>>    struct acpi_resource_irq,
>>    struct acpi_resource_extended_irq.
>> 
>> In theory only the extended version can contain multiple IRQs, but
>> the Linux
>> ACPI core accommodates non-compliant DSDT tables that have regular
>> IRQ resources
>> contain multiple IRQs.
>> 
>> To better explain, suppose you have a device that handles two GSIs
>> and one
>> other IRQ form a separate device:
>> 
>>    Interrupt (ResourceConsumer, Level, ActiveHigh, Exclusive, 0x00, )
>>    { 130, 131 }
>> 
>>    Interrupt (ResourceConsumer, Level, ActiveHigh, Exclusive, 0x00,
>> "\\_SB.TCS0.QIC0", )
>>    { 4 }
>> 
>> These are encoded into two separate structures with their own
>> interrupts array:
>> 
>>   res0.interrupts[] = { 130, 131 }
>>   res1.interrupts[] = { 4 }
>> 
>> However, from the perspective of a client driver these are indexed
>> into a flat space:
>> 
>>   [0] -> 130
>>   [1] -> 131
>>   [2] -> 4
>> 
>> Now say mapping of IRQ 4 failed during bus scan. When acpi_irq_get
>> retries to map it, the client code will pass index 2.
>> acpi_walk_resources will call acpi_irq_get_cb with the first IRQ
>> resource. If the index is less than the number of IRQs, we know this
>> IRQ resource contains the IRQ we want so we call
>> acpi_dev_resource_interrupt to do the actual mapping and return
>> AE_CTRL_TERMINATE so acpi_walk_resources does not continue walking the
>> resource buffer. On the other hand if the index is equal or larger it
>> means we need to skip this IRQ resource and look at the next one, but
>> we need to adjust the lookup index to that of the next IRQ resource.
>> 
>> Makes sense?
> 
> Yes, basically it is to create a linear index out of multiple 
> resources,
> the DT case is simpler since you get the interrupt out of a single
> property that we can easily index (ie we have to know which firmware
> entry corresponds to the resource that we are retrying). That deserves
> a comment.
> 

Good point. I will add the comment on the next version of the series,
however, I will hold a few days for more feedback before I submit that.

Thanks,
Agustin

> Thanks for explaining.
> 
> Lorenzo
> 
>> >>+		break;
>> >>+	case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
>> >>+		ext_irq = &ares->data.extended_irq;
>> >>+		if (ctx->index < ext_irq->interrupt_count) {
>> >>+			acpi_dev_resource_interrupt(ares, ctx->index, ctx->res);
>> >>+			return AE_CTRL_TERMINATE;
>> >>+		}
>> >>+		ctx->index -= ext_irq->interrupt_count;
>> >
>> >Ditto.
>> 
>> The same logic is used for both types of resources because they are
>> handled in
>> the same way by the ACPI core when it comes to indexing.
>> 
>> Thanks,
>> Agustin
>> 
>> >
>> >Thanks,
>> >Lorenzo
>> >
>> >>+		break;
>> >>+	}
>> >>+
>> >>+	return AE_OK;
>> >>+}
>> >>+
>> >>+/**
>> >>+ * acpi_irq_get - Look for the ACPI IRQ resource with the given
>> >>index and
>> >>+ *                use it to initialize the given Linux IRQ resource.
>> >>+ * @handle ACPI device handle
>> >>+ * @index  ACPI IRQ resource index to lookup
>> >>+ * @res    Linux IRQ resource to initialize
>> >>+ *
>> >>+ * Return: 0 on success
>> >>+ *         -EINVAL if an error occurs
>> >>+ *         -EPROBE_DEFER if the IRQ lookup/conversion failed
>> >>+ */
>> >>+int acpi_irq_get(acpi_handle handle, unsigned int index, struct
>> >>resource *res)
>> >>+{
>> >>+	struct acpi_irq_get_ctx ctx = { index, res };
>> >>+	acpi_status status;
>> >>+
>> >>+	status = acpi_walk_resources(handle, METHOD_NAME__CRS,
>> >>+				     acpi_irq_get_cb, &ctx);
>> >>+	if (ACPI_FAILURE(status))
>> >>+		return -EINVAL;
>> >>+	if (res->flags & IORESOURCE_DISABLED)
>> >>+		return -EPROBE_DEFER;
>> >>+	return 0;
>> >>+}
>> >>+EXPORT_SYMBOL_GPL(acpi_irq_get);
>> >>diff --git a/drivers/base/platform.c b/drivers/base/platform.c
>> >>index c4af003..61423d2 100644
>> >>--- a/drivers/base/platform.c
>> >>+++ b/drivers/base/platform.c
>> >>@@ -102,6 +102,14 @@ int platform_get_irq(struct platform_device
>> >>*dev, unsigned int num)
>> >> 	}
>> >>
>> >> 	r = platform_get_resource(dev, IORESOURCE_IRQ, num);
>> >>+	if (r && r->flags & IORESOURCE_DISABLED &&
>> >>ACPI_COMPANION(&dev->dev)) {
>> >>+		int ret;
>> >>+
>> >>+		ret = acpi_irq_get(ACPI_HANDLE(&dev->dev), num, r);
>> >>+		if (ret)
>> >>+			return ret;
>> >>+	}
>> >>+
>> >> 	/*
>> >> 	 * The resources may pass trigger flags to the irqs that need
>> >> 	 * to be set up. It so happens that the trigger flags for
>> >>@@ -1450,4 +1458,3 @@ void __init early_platform_cleanup(void)
>> >> 		memset(&pd->dev.devres_head, 0, sizeof(pd->dev.devres_head));
>> >> 	}
>> >> }
>> >>-
>> >>diff --git a/include/linux/acpi.h b/include/linux/acpi.h
>> >>index 689a8b9..325bdb9 100644
>> >>--- a/include/linux/acpi.h
>> >>+++ b/include/linux/acpi.h
>> >>@@ -406,6 +406,7 @@ bool
>> >>acpi_dev_resource_ext_address_space(struct acpi_resource *ares,
>> >> unsigned int acpi_dev_get_irq_type(int triggering, int polarity);
>> >> bool acpi_dev_resource_interrupt(struct acpi_resource *ares,
>> >>int index,
>> >> 				 struct resource *res);
>> >>+int acpi_irq_get(acpi_handle handle, unsigned int index, struct
>> >>resource *res);
>> >>
>> >> void acpi_dev_free_resource_list(struct list_head *list);
>> >> int acpi_dev_get_resources(struct acpi_device *adev, struct
>> >>list_head *list,
>> >>@@ -763,6 +764,12 @@ static inline int
>> >>acpi_reconfig_notifier_unregister(struct notifier_block *nb)
>> >> 	return -EINVAL;
>> >> }
>> >>
>> >>+static inline int acpi_irq_get(acpi_handle handle, unsigned int
>> >>index,
>> >>+			       struct resource *res)
>> >>+{
>> >>+	return -EINVAL;
>> >>+}
>> >>+
>> >> #endif	/* !CONFIG_ACPI */
>> >>
>> >> #ifdef CONFIG_ACPI_HOTPLUG_IOAPIC
>> >>--
>> >>Qualcomm Datacenter Technologies, Inc. on behalf of the Qualcomm
>> >>Technologies, Inc.
>> >>Qualcomm Technologies, Inc. is a member of the Code Aurora
>> >>Forum, a Linux Foundation Collaborative Project.
>> >>
>> >>--
>> >>To unsubscribe from this list: send the line "unsubscribe
>> >>linux-acpi" in
>> >>the body of a message to majordomo@...r.kernel.org
>> >>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> 
>> --
>> Qualcomm Datacenter Technologies, Inc. on behalf of the Qualcomm
>> Technologies, Inc.
>> Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a
>> Linux Foundation Collaborative Project.

-- 
Qualcomm Datacenter Technologies, Inc. on behalf of the Qualcomm 
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a 
Linux Foundation Collaborative Project.

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