[PATCH 7/9] of/platform: Resolve interrupt references at probe time

[Thierry Reding <thierry.reding@gmail.com>]

Interrupt references are currently resolved very early (when a device is
created). This has the disadvantage that it will fail in cases where the
interrupt parent hasn't been probed and no IRQ domain for it has been
registered yet. To work around that various drivers use explicit
initcall ordering to force interrupt parents to be probed before devices
that need them are created. That's error prone and doesn't always work.
If a platform device uses an interrupt line connected to a different
platform device (such as a GPIO controller), both will be created in the
same batch, and the GPIO controller won't have been probed by its driver
when the depending platform device is created. Interrupt resolution will
fail in that case.

Another common workaround is for drivers to explicitly resolve interrupt
references at probe time. This is suboptimal, however, because it will
require every driver to duplicate the code.

This patch adds support for late interrupt resolution to the platform
driver core, by resolving the references right before a device driver's
.probe() function will be called. This not only delays the resolution
until a much later time (giving interrupt parents a better chance of
being probed in the meantime), but it also allows the platform driver
core to queue the device for deferred probing if the interrupt parent
hasn't registered its IRQ domain yet.

Signed-off-by: Thierry Reding <treding@nvidia.com>
---
 drivers/base/platform.c     |  4 ++++
 drivers/of/platform.c       | 43 +++++++++++++++++++++++++++++++++++++------
 include/linux/of_platform.h |  7 +++++++
 3 files changed, 48 insertions(+), 6 deletions(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 4f8bef3..8dcf835 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -481,6 +481,10 @@ static int platform_drv_probe(struct device *_dev)
 	struct platform_device *dev = to_platform_device(_dev);
 	int ret;
 
+	ret = of_platform_probe(dev);
+	if (ret)
+		return ret;
+
 	if (ACPI_HANDLE(_dev))
 		acpi_dev_pm_attach(_dev, true);
 
diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index 9b439ac..edaef70 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -142,7 +142,7 @@ struct platform_device *of_device_alloc(struct device_node *np,
 				  struct device *parent)
 {
 	struct platform_device *dev;
-	int rc, i, num_reg = 0, num_irq;
+	int rc, i, num_reg = 0;
 	struct resource *res, temp_res;
 
 	dev = platform_device_alloc("", -1);
@@ -153,23 +153,21 @@ struct platform_device *of_device_alloc(struct device_node *np,
 	if (of_can_translate_address(np))
 		while (of_address_to_resource(np, num_reg, &temp_res) == 0)
 			num_reg++;
-	num_irq = of_irq_count(np);
 
 	/* Populate the resource table */
-	if (num_irq || num_reg) {
-		res = kzalloc(sizeof(*res) * (num_irq + num_reg), GFP_KERNEL);
+	if (num_reg) {
+		res = kzalloc(sizeof(*res) * num_reg, GFP_KERNEL);
 		if (!res) {
 			platform_device_put(dev);
 			return NULL;
 		}
 
-		dev->num_resources = num_reg + num_irq;
+		dev->num_resources = num_reg;
 		dev->resource = res;
 		for (i = 0; i < num_reg; i++, res++) {
 			rc = of_address_to_resource(np, i, res);
 			WARN_ON(rc);
 		}
-		WARN_ON(of_irq_to_resource_table(np, res, num_irq) != num_irq);
 	}
 
 	dev->dev.of_node = of_node_get(np);
@@ -490,4 +488,37 @@ int of_platform_populate(struct device_node *root,
 	return rc;
 }
 EXPORT_SYMBOL_GPL(of_platform_populate);
+
+int of_platform_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	int num_irq, ret = 0;
+
+	if (!pdev->dev.of_node)
+		return 0;
+
+	num_irq = of_irq_count(pdev->dev.of_node);
+	if (num_irq > 0) {
+		struct resource *res = pdev->resource;
+		int num_reg = pdev->num_resources;
+		int num = num_reg + num_irq;
+
+		res = krealloc(res, num * sizeof(*res), GFP_KERNEL);
+		if (!res)
+			return -ENOMEM;
+
+		pdev->num_resources = num;
+		pdev->resource = res;
+		res += num_reg;
+
+		ret = of_irq_to_resource_table(np, res, num_irq);
+		if (ret < 0)
+			return ret;
+
+		WARN_ON(ret != num_irq);
+		ret = 0;
+	}
+
+	return ret;
+}
 #endif /* CONFIG_OF_ADDRESS */
diff --git a/include/linux/of_platform.h b/include/linux/of_platform.h
index 05cb4a9..92fc4f6 100644
--- a/include/linux/of_platform.h
+++ b/include/linux/of_platform.h
@@ -72,6 +72,8 @@ extern int of_platform_populate(struct device_node *root,
 				const struct of_device_id *matches,
 				const struct of_dev_auxdata *lookup,
 				struct device *parent);
+
+extern int of_platform_probe(struct platform_device *pdev);
 #else
 static inline int of_platform_populate(struct device_node *root,
 					const struct of_device_id *matches,
@@ -80,6 +82,11 @@ static inline int of_platform_populate(struct device_node *root,
 {
 	return -ENODEV;
 }
+
+static inline int of_platform_probe(struct platform_device *pdev)
+{
+	return 0;
+}
 #endif
 
 #endif	/* _LINUX_OF_PLATFORM_H */
-- 
1.8.4