dm: Introduce DMA constraints into the core device model

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@suse.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Peter Robinson <pbrobinson@gmail.com>
Signed-off-by: Matthias Brugger <mbrugger@suse.com>

2 files changed, 51 insertions, 0 deletions

diff --git a/drivers/core/Kconfig b/drivers/core/Kconfig
index dbfe51c6e87..00554af4995 100644
--- a/drivers/core/Kconfig
+++ b/drivers/core/Kconfig
@@ -129,6 +129,16 @@ config TPL_DM_INLINE_OFNODE
 	  This applies to several ofnode functions (see ofnode.h) which are
 	  seldom used. Inlining them can help reduce code size.
 
+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 82a00989604..625134921d6 100644
--- a/drivers/core/device.c
+++ b/drivers/core/device.c
@@ -422,6 +422,43 @@ fail:
 	return ret;
 }
 
+/**
+ * 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 (!CONFIG_IS_ENABLED(DM_DMA) || !parent || !dev_has_ofnode(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_set_dma_offset(dev, cpu - bus);
+
+	return 0;
+}
+
 int device_probe(struct udevice *dev)
 {
 	const struct driver *drv;
@@ -484,6 +521,10 @@ 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;