[PATCH v2] of/fdt: Allow memory node and root to have different size/address cells

From: Vineet Gupta
Date: Thu Oct 01 2015 - 08:19:05 EST


Currently memory node parsing uses root "#size-cells", "#address-cells"
This doesn't work correctly when memory address/size is different or
greater than root's.

e.g. ARC 32-bit systems implementing physical adressing extension and
say 4GB of memory. All peripherals mappings stay within the 4GB (so root
address/size cells remain 1 each), only the memory node address/size
cells needs to specify greater than 32-bits as below

memory {
device_type = "memory";
reg = <0x0 0x80000000 0x1 0x00000000>; /* 4 GB */
#address-cells = <2>;
#size-cells = <2>;
};

This patch lets me boot a ARC system with PAE40 + 4GB of memory specified
as above and fails to boot otherwise as memory parsing doesn't populate
right base, size.

---
Changes since v2:
silly typo creeped in due to last minute change to use root props
---
Cc: Grant Likely <grant.likely@xxxxxxxxxx>
Cc: Rob Herring <robh+dt@xxxxxxxxxx>
Cc: devicetree@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-arch@xxxxxxxxxxxxxxx
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
---
drivers/of/fdt.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 07496560e5b9..48618bb2674a 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -888,8 +888,8 @@ int __init early_init_dt_scan_memory(unsigned long node, const char *uname,
int depth, void *data)
{
const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
- const __be32 *reg, *endp;
- int l;
+ const __be32 *reg, *endp, *prop;
+ int l, dt_mem_addr_cells, dt_mem_size_cells;

/* We are scanning "memory" nodes only */
if (type == NULL) {
@@ -912,11 +912,22 @@ int __init early_init_dt_scan_memory(unsigned long node, const char *uname,

pr_debug("memory scan node %s, reg size %d,\n", uname, l);

- while ((endp - reg) >= (dt_root_addr_cells + dt_root_size_cells)) {
+
+ dt_mem_size_cells = dt_root_size_cells;
+ prop = of_get_flat_dt_prop(node, "#size-cells", NULL);
+ if (prop)
+ dt_mem_size_cells = be32_to_cpup(prop);
+
+ dt_mem_addr_cells = dt_root_addr_cells;
+ prop = of_get_flat_dt_prop(node, "#address-cells", NULL);
+ if (prop)
+ dt_mem_addr_cells = be32_to_cpup(prop);
+
+ while ((endp - reg) >= (dt_mem_addr_cells + dt_mem_size_cells)) {
u64 base, size;

- base = dt_mem_next_cell(dt_root_addr_cells, &reg);
- size = dt_mem_next_cell(dt_root_size_cells, &reg);
+ base = dt_mem_next_cell(dt_mem_addr_cells, &reg);
+ size = dt_mem_next_cell(dt_mem_size_cells, &reg);

if (size == 0)
continue;
--
1.9.1

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