[PATCHv5 2/9] driver/core: populate devices in order for IOMMUs

[Hiroshi Doyu <hdoyu-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

IOMMU devices on the bus need to be poplulated first, then iommu
master devices are done later.

With CONFIG_OF_IOMMU, "iommus=" DT binding would be used to identify
whether a device can be an iommu msater or not. If a device can, we'll
defer to populate that device till an iommu device is populated. Once
an iommu device is populated, "dev->bus->iommu_ops" is set in the
bus. Then, those defered iommu master devices are populated and
configured for IOMMU with help of the already populated iommu device
via iommu_ops->add_device(). Multiple IOMMUs can be listed on this
"iommus" binding so that a device can have multiple IOMMUs attached.

Signed-off-by: Hiroshi Doyu <hdoyu-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
---
v5:
Use "iommus=" binding instread of arm,smmu's "#stream-id-cells".

v4:
This is newly added, and the successor of the following RFC:
  [RFC][PATCHv3+ 1/2] driver/core: Add of_iommu_attach()
  http://lists.linuxfoundation.org/pipermail/iommu/2013-November/006914.html
---
 drivers/base/dd.c        |  5 +++++
 drivers/iommu/of_iommu.c | 22 ++++++++++++++++++++++
 include/linux/of_iommu.h |  7 +++++++
 3 files changed, 34 insertions(+)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 35fa368..6e892d4 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -25,6 +25,7 @@
 #include <linux/async.h>
 #include <linux/pm_runtime.h>
 #include <linux/pinctrl/devinfo.h>
+#include <linux/of_iommu.h>
 
 #include "base.h"
 #include "power/power.h"
@@ -273,6 +274,10 @@ static int really_probe(struct device *dev, struct device_driver *drv)
 
 	dev->driver = drv;
 
+	ret = of_iommu_attach(dev);
+	if (ret)
+		goto probe_failed;
+
 	/* If using pinctrl, bind pins now before probing */
 	ret = pinctrl_bind_pins(dev);
 	if (ret)
diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index ee249bc..4aef2b2 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -20,6 +20,8 @@
 #include <linux/export.h>
 #include <linux/limits.h>
 #include <linux/of.h>
+#include <linux/device.h>
+#include <linux/iommu.h>
 
 /**
  * of_get_dma_window - Parse *dma-window property and returns 0 if found.
@@ -88,3 +90,23 @@ int of_get_dma_window(struct device_node *dn, const char *prefix, int index,
 	return 0;
 }
 EXPORT_SYMBOL_GPL(of_get_dma_window);
+
+int of_iommu_attach(struct device *dev)
+{
+	int i;
+	struct of_phandle_args args;
+	struct iommu_ops *ops = dev->bus->iommu_ops;
+
+	of_property_for_each_phandle_with_args(dev->of_node, "iommus",
+					       "#iommu-cells", i, &args) {
+		pr_debug("%s(i=%d) ops=%p %s\n",
+			 __func__, i, ops, dev_name(dev));
+
+		if (!ops)
+			return -EPROBE_DEFER;
+	}
+
+	if (i && ops->add_device)
+		return ops->add_device(dev);
+	return 0;
+}
diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index 51a560f..3457489 100644
--- a/include/linux/of_iommu.h
+++ b/include/linux/of_iommu.h
@@ -7,6 +7,8 @@ extern int of_get_dma_window(struct device_node *dn, const char *prefix,
 			     int index, unsigned long *busno, dma_addr_t *addr,
 			     size_t *size);
 
+extern int of_iommu_attach(struct device *dev);
+
 #else
 
 static inline int of_get_dma_window(struct device_node *dn, const char *prefix,
@@ -16,6 +18,11 @@ static inline int of_get_dma_window(struct device_node *dn, const char *prefix,
 	return -EINVAL;
 }
 
+static inline int of_iommu_attach(struct device *dev)
+{
+	return 0;
+}
+
 #endif	/* CONFIG_OF_IOMMU */
 
 #endif /* __OF_IOMMU_H */
-- 
1.8.1.5