[PATCH v4 06/13] 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>
Reviewed-by: Simon Glass <sjg at chromium.org>

---
Changes since v2:
 - Comment functions and struct variables
 - Correct typos

Changes since v2:
 - Return/Fail on error
 - Add config option
 - use ulong instead for u64 for dev->dma_offset

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

 drivers/core/Kconfig  | 10 ++++++++++
 drivers/core/device.c | 45 +++++++++++++++++++++++++++++++++++++++++++
 include/dm/device.h   |  5 +++++
 3 files changed, 60 insertions(+)

diff --git a/drivers/core/Kconfig b/drivers/core/Kconfig
index ffae6f9795..295cf2dd00 100644
--- a/drivers/core/Kconfig
+++ b/drivers/core/Kconfig
@@ -113,6 +113,16 @@ config SPL_DM_SEQ_ALIAS
 	  numbered devices (e.g. serial0 = &serial0). This feature can be
 	  disabled if it is not required, to save code space in SPL.
 
+config DM_DMA
+	bool "Support per-device DMA constraints"
+	depends on DM
+	default n
+	help
+	  Enable this to extract per-device DMA constraints, only supported on
+	  device-tree systems for now. This is needed in order translate
+	  addresses on systems where different buses have different views of
+	  the physical address space.
+
 config REGMAP
 	bool "Support register maps"
 	depends on DM
diff --git a/drivers/core/device.c b/drivers/core/device.c
index 4b3dcb3b37..e88a999960 100644
--- a/drivers/core/device.c
+++ b/drivers/core/device.c
@@ -421,6 +421,47 @@ fail:
 	return ret;
 }
 
+#if CONFIG_IS_ENABLED(DM_DMA)
+/**
+ * device_get_dma_constraints() - Populate device's DMA constraints
+ *
+ * Gets a device's DMA constraints from firmware. This information is later
+ * used by drivers to translate physcal addresses to the device's bus address
+ * space. For now only device-tree is supported.
+ *
+ * @dev: Pointer to target device
+ * Return: 0 if OK or if no DMA constraints were found, error otherwise
+ */
+static int device_get_dma_constraints(struct udevice *dev)
+{
+	struct udevice *parent = dev->parent;
+	phys_addr_t cpu = 0;
+	dma_addr_t bus = 0;
+	u64 size = 0;
+	int ret;
+
+	if (!parent || !dev_of_valid(parent))
+		return 0;
+
+	/*
+	 * We start parsing for dma-ranges from the device's bus node. This is
+	 * specially important on nested buses.
+	 */
+	ret = dev_get_dma_range(parent, &cpu, &bus, &size);
+	/* Don't return an error if no 'dma-ranges' were found */
+	if (ret && ret != -ENOENT) {
+		dm_warn("%s: failed to get DMA range, %d\n", dev->name, ret);
+		return ret;
+	}
+
+	dev->dma_offset = cpu - bus;
+
+	return 0;
+}
+#else
+static int device_get_dma_constraints(struct udevice *dev) { return 0; }
+#endif
+
 int device_probe(struct udevice *dev)
 {
 	const struct driver *drv;
@@ -482,6 +523,10 @@ int device_probe(struct udevice *dev)
 			goto fail;
 	}
 
+	ret = device_get_dma_constraints(dev);
+	if (ret)
+		goto fail;
+
 	ret = uclass_pre_probe_device(dev);
 	if (ret)
 		goto fail;
diff --git a/include/dm/device.h b/include/dm/device.h
index 5bef484247..f51d274c82 100644
--- a/include/dm/device.h
+++ b/include/dm/device.h
@@ -138,6 +138,8 @@ enum {
  *		When CONFIG_DEVRES is enabled, devm_kmalloc() and friends will
  *		add to this list. Memory so-allocated will be freed
  *		automatically when the device is removed / unbound
+ * @dma_offset: Offset between the physical address space (CPU's) and the
+ *		device's bus address space
  */
 struct udevice {
 	const struct driver *driver;
@@ -161,6 +163,9 @@ struct udevice {
 #ifdef CONFIG_DEVRES
 	struct list_head devres_head;
 #endif
+#ifdef CONFIG_DM_DMA
+	ulong dma_offset;
+#endif
 };
 
 /* Maximum sequence number supported */
-- 
2.29.2