Re: [PATCH V7 1/3] ACPI: Retry IRQ conversion if it failed previously

[Lorenzo Pieralisi]

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@xxxxxxxxxxxxxx>
> >>---
> >> 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.

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.
> >>
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> 
> -- 
> 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.