[PATCH v2 5/8] dm: Introduce DMA constraints into the core device model

[Nicolas Saenz Julienne]

Calculating the DMA offset between a bus address space and CPU's every
time we call phys_to_bus() and bus_to_phys() isn't ideal performance
wise, as it implies traversing the device tree from the device's node up
to the root. Since this information is static and available before the
device's initialization, parse it before the probe call an provide the
DMA offset in 'struct udevice' for the address translation code to use
it.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne at suse.de>

---
Changes since v1:
 - Update commit message so as to explain better the reasoning behind
   this

 drivers/core/device.c | 24 ++++++++++++++++++++++++
 include/dm/device.h   |  1 +
 2 files changed, 25 insertions(+)

diff --git a/drivers/core/device.c b/drivers/core/device.c
index 4b3dcb3b37..4255bea24d 100644
--- a/drivers/core/device.c
+++ b/drivers/core/device.c
@@ -421,6 +421,28 @@ fail:
 	return ret;
 }
 
+void device_get_dma_constraints(struct udevice *dev)
+{
+	phys_addr_t cpu;
+	dma_addr_t bus;
+	u64 size;
+	int ret;
+
+	if (!dev_of_valid(dev))
+		return;
+
+	ret = dev_get_dma_range(dev, &cpu, &bus, &size);
+	if (ret) {
+		/* Don't complain if no 'dma-ranges' were found */
+		if (ret != -ENODEV)
+			dm_warn("%s: failed to get DMA range, %d\n",
+				dev->name, ret);
+		return;
+	}
+
+	dev->dma_offset = cpu - bus;
+}
+
 int device_probe(struct udevice *dev)
 {
 	const struct driver *drv;
@@ -482,6 +504,8 @@ int device_probe(struct udevice *dev)
 			goto fail;
 	}
 
+	device_get_dma_constraints(dev);
+
 	ret = uclass_pre_probe_device(dev);
 	if (ret)
 		goto fail;
diff --git a/include/dm/device.h b/include/dm/device.h
index 5bef484247..59f711e3dd 100644
--- a/include/dm/device.h
+++ b/include/dm/device.h
@@ -161,6 +161,7 @@ struct udevice {
 #ifdef CONFIG_DEVRES
 	struct list_head devres_head;
 #endif
+	u64 dma_offset;
 };
 
 /* Maximum sequence number supported */
-- 
2.29.2