[PATCH v3 3/8] of/address: Introduce of_dma_get_max_cpu_address()

Nicolas Saenz Julienne
2020-10-14T19:12:30Z

Introduce of_dma_get_max_cpu_address(), which provides the highest CPU
physical address addressable by all DMA masters in the system. It's
specially useful for setting memory zones sizes at early boot time.

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

---

Changes since v2:
- Use PHYS_ADDR_MAX
- return phys_dma_t
- Rename function
- Correct subject
- Add support to start parsing from an arbitrary device node in order
for the function to work with unit tests

drivers/of/address.c | 42 ++++++++++++++++++++++++++++++++++++++++++
include/linux/of.h | 7 +++++++
2 files changed, 49 insertions(+)

diff --git a/drivers/of/address.c b/drivers/of/address.c
index eb9ab4f1e80b..b5a9695aaf82 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -1024,6 +1024,48 @@ int of_dma_get_range(struct device_node *np, const struct bus_dma_region **map)
}
#endif /* CONFIG_HAS_DMA */

+/**
+ * of_dma_get_max_cpu_address - Gets highest CPU address suitable for DMA
+ * @np: The node to start searching from or NULL to start from the root
+ *
+ * Gets the highest CPU physical address that is addressable by all DMA masters
+ * in the system (or subtree when np is non-NULL). If no DMA constrained device
+ * is found, it returns PHYS_ADDR_MAX.
+ */
+phys_addr_t __init of_dma_get_max_cpu_address(struct device_node *np)
+{
+ phys_addr_t max_cpu_addr = PHYS_ADDR_MAX;
+ struct of_range_parser parser;
+ phys_addr_t subtree_max_addr;
+ struct device_node *child;
+ phys_addr_t cpu_end = 0;
+ struct of_range range;
+ const __be32 *ranges;
+ int len;
+
+ if (!np)
+ np = of_root;
+
+ ranges = of_get_property(np, "dma-ranges", &len);
+ if (ranges && len) {
+ of_dma_range_parser_init(&parser, np);
+ for_each_of_range(&parser, &range)
+ if (range.cpu_addr + range.size > cpu_end)
+ cpu_end = range.cpu_addr + range.size;
+
+ if (max_cpu_addr > cpu_end)
+ max_cpu_addr = cpu_end;
+ }
+
+ for_each_available_child_of_node(np, child) {
+ subtree_max_addr = of_dma_get_max_cpu_address(child);
+ if (max_cpu_addr > subtree_max_addr)
+ max_cpu_addr = subtree_max_addr;
+ }
+
+ return max_cpu_addr;
+}
+
/**
* of_dma_is_coherent - Check if device is coherent
* @np: device node
diff --git a/include/linux/of.h b/include/linux/of.h
index 481ec0467285..db8db8f2c967 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -558,6 +558,8 @@ int of_map_id(struct device_node *np, u32 id,
const char *map_name, const char *map_mask_name,
struct device_node **target, u32 *id_out);

+phys_addr_t of_dma_get_max_cpu_address(struct device_node *np);
+
#else /* CONFIG_OF */

static inline void of_core_init(void)
@@ -995,6 +997,11 @@ static inline int of_map_id(struct device_node *np, u32 id,
return -EINVAL;
}

+static inline phys_addr_t of_dma_get_max_cpu_address(struct device_node *np)
+{
+ return PHYS_ADDR_MAX;
+}
+
#define of_match_ptr(_ptr) NULL
#define of_match_node(_matches, _node) NULL
#endif /* CONFIG_OF */
--
2.28.0