[PATCH RFC v2 2/5] of: get dma area lower limit
From: Baruch Siach
Date: Tue Apr 09 2024 - 02:26:08 EST
of_dma_get_max_cpu_address() returns the highest CPU address that
devices can use for DMA. The implicit assumption is that all CPU
addresses below that limit are suitable for DMA. However the
'dma-ranges' property this code uses also encodes a lower limit for DMA
that is potentially non zero.
Rename to of_dma_get_cpu_limits(), and extend to retrieve also the lower
limit for the same 'dma-ranges' property describing the high limit.
Update callers of of_dma_get_max_cpu_address(). No functional change
intended.
Signed-off-by: Baruch Siach <baruch@xxxxxxxxxx>
---
arch/arm64/mm/init.c | 2 +-
drivers/of/address.c | 38 +++++++++++++++++++++++++++-----------
drivers/of/unittest.c | 8 ++++----
include/linux/of.h | 11 ++++++++---
4 files changed, 40 insertions(+), 19 deletions(-)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 00508c69ca9e..77e942ca578b 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -128,7 +128,7 @@ static void __init zone_sizes_init(void)
#ifdef CONFIG_ZONE_DMA
acpi_zone_dma_limit = acpi_iort_dma_get_max_cpu_address();
- dt_zone_dma_limit = of_dma_get_max_cpu_address(NULL);
+ of_dma_get_cpu_limits(NULL, &dt_zone_dma_limit, NULL);
zone_dma_limit = min(dt_zone_dma_limit, acpi_zone_dma_limit);
arm64_dma_phys_limit = max_zone_phys(zone_dma_limit);
max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
diff --git a/drivers/of/address.c b/drivers/of/address.c
index ae46a3605904..ac009b3bb63b 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -964,21 +964,25 @@ 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
+ * of_dma_get_cpu_limits - Gets highest CPU address suitable for DMA
* @np: The node to start searching from or NULL to start from the root
+ * @max: Pointer to high address limit or NULL if not needed
+ * @min: Pointer to low address limit or NULL if not needed
*
* Gets the highest CPU physical address that is addressable by all DMA masters
- * in the sub-tree pointed by np, or the whole tree if NULL is passed. If no
- * DMA constrained device is found, it returns PHYS_ADDR_MAX.
+ * in the sub-tree pointed by np, or the whole tree if @np in NULL. If no
+ * DMA constrained device is found, @*max is PHYS_ADDR_MAX, and @*low is 0.
*/
-phys_addr_t __init of_dma_get_max_cpu_address(struct device_node *np)
+void __init of_dma_get_cpu_limits(struct device_node *np,
+ phys_addr_t *max, phys_addr_t *min)
{
phys_addr_t max_cpu_addr = PHYS_ADDR_MAX;
struct of_range_parser parser;
- phys_addr_t subtree_max_addr;
+ phys_addr_t min_cpu_addr = 0;
struct device_node *child;
struct of_range range;
const __be32 *ranges;
+ u64 cpu_start = 0;
u64 cpu_end = 0;
int len;
@@ -988,21 +992,33 @@ phys_addr_t __init of_dma_get_max_cpu_address(struct device_node *np)
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)
+ for_each_of_range(&parser, &range) {
+ if (range.cpu_addr + range.size > cpu_end) {
cpu_end = range.cpu_addr + range.size - 1;
+ cpu_start = range.cpu_addr;
+ }
+ }
- if (max_cpu_addr > cpu_end)
+ if (max_cpu_addr > cpu_end) {
max_cpu_addr = cpu_end;
+ min_cpu_addr = cpu_start;
+ }
}
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)
+ phys_addr_t subtree_max_addr, subtree_min_addr;
+
+ of_dma_get_cpu_limits(child, &subtree_max_addr, &subtree_min_addr);
+ if (max_cpu_addr > subtree_max_addr) {
max_cpu_addr = subtree_max_addr;
+ min_cpu_addr = subtree_min_addr;
+ }
}
- return max_cpu_addr;
+ if (max)
+ *max = max_cpu_addr;
+ if (min)
+ *min = min_cpu_addr;
}
/**
diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c
index 6b5c36b6a758..2d632d4ec5b1 100644
--- a/drivers/of/unittest.c
+++ b/drivers/of/unittest.c
@@ -921,7 +921,7 @@ static void __init of_unittest_changeset(void)
#endif
}
-static void __init of_unittest_dma_get_max_cpu_address(void)
+static void __init of_unittest_dma_get_cpu_limits(void)
{
struct device_node *np;
phys_addr_t cpu_addr;
@@ -935,9 +935,9 @@ static void __init of_unittest_dma_get_max_cpu_address(void)
return;
}
- cpu_addr = of_dma_get_max_cpu_address(np);
+ of_dma_get_cpu_limits(np, &cpu_addr, NULL);
unittest(cpu_addr == 0x4fffffff,
- "of_dma_get_max_cpu_address: wrong CPU addr %pad (expecting %x)\n",
+ "of_dma_get_cpu_limits: wrong CPU addr %pad (expecting %x)\n",
&cpu_addr, 0x4fffffff);
}
@@ -4109,7 +4109,7 @@ static int __init of_unittest(void)
of_unittest_changeset();
of_unittest_parse_interrupts();
of_unittest_parse_interrupts_extended();
- of_unittest_dma_get_max_cpu_address();
+ of_unittest_dma_get_cpu_limits();
of_unittest_parse_dma_ranges();
of_unittest_pci_dma_ranges();
of_unittest_bus_ranges();
diff --git a/include/linux/of.h b/include/linux/of.h
index a0bedd038a05..7756441d3ce0 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -454,7 +454,8 @@ 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);
+void of_dma_get_cpu_limits(struct device_node *np, phys_addr_t *max,
+ phys_addr_t *min);
struct kimage;
void *of_kexec_alloc_and_setup_fdt(const struct kimage *image,
@@ -880,9 +881,13 @@ 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)
+static inline void of_dma_get_cpu_limits(struct device_node *np,
+ phys_addr_t *max, phys_addr_t *min)
{
- return PHYS_ADDR_MAX;
+ if (max)
+ *max = PHYS_ADDR_MAX;
+ if (min)
+ *min = 0;
}
static inline const void *of_device_get_match_data(const struct device *dev)
--
2.43.0