The FDT specification [0] gives a requirement of aligning properties on 32-bits. Make sure that the compiler is aware of this constraint when accessing 64-bits properties.
[0]: https://github.com/devicetree-org/devicetree-specification/blob/master/sourc...
Signed-off-by: Jean-Jacques Hiblot jjhiblot@ti.com ---
Here is a portion of the disassembly of ofnode_read_u64(). It show the effect of the patch on ARM64.
with the classic fdt64_t type. GCC emits LDR (load register) 34: 54000109 b.ls 54 <ofnode_read_u64+0x54> // b.plast 38: f9400000 ldr x0, [x0] 3c: dac00c00 rev x0, x0
with the unaligned_fdt64_t type. GCC emits LDP (Load Pair of registers) 34: 54000129 b.ls 58 <ofnode_read_u64+0x58> // b.plast 38: 29400001 ldp w1, w0, [x0] 3c: aa008020 orr x0, x1, x0, lsl #32 40: dac00c00 rev x0, x0
common/fdt_support.c | 2 +- drivers/core/ofnode.c | 2 +- include/linux/libfdt_env.h | 1 + lib/fdtdec.c | 2 +- 4 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/common/fdt_support.c b/common/fdt_support.c index baf7924ff6..6834399039 100644 --- a/common/fdt_support.c +++ b/common/fdt_support.c @@ -1566,7 +1566,7 @@ static int fdt_read_prop(const fdt32_t *prop, int prop_len, int cell_off, uint64_t *val, int cells) { const fdt32_t *prop32 = &prop[cell_off]; - const fdt64_t *prop64 = (const fdt64_t *)&prop[cell_off]; + const unaligned_fdt64_t *prop64 = (const fdt64_t *)&prop[cell_off];
if ((cell_off + cells) > prop_len) return -FDT_ERR_NOSPACE; diff --git a/drivers/core/ofnode.c b/drivers/core/ofnode.c index 297f0a0c7c..8f0eab2ca6 100644 --- a/drivers/core/ofnode.c +++ b/drivers/core/ofnode.c @@ -57,7 +57,7 @@ int ofnode_read_s32_default(ofnode node, const char *propname, s32 def)
int ofnode_read_u64(ofnode node, const char *propname, u64 *outp) { - const fdt64_t *cell; + const unaligned_fdt64_t *cell; int len;
assert(ofnode_valid(node)); diff --git a/include/linux/libfdt_env.h b/include/linux/libfdt_env.h index e2bf79c7ee..e49fcd72bd 100644 --- a/include/linux/libfdt_env.h +++ b/include/linux/libfdt_env.h @@ -16,6 +16,7 @@ typedef __be16 fdt16_t; typedef __be32 fdt32_t; typedef __be64 fdt64_t; +typedef __be64 unaligned_fdt64_t __aligned(4);
#define fdt32_to_cpu(x) be32_to_cpu(x) #define cpu_to_fdt32(x) cpu_to_be32(x) diff --git a/lib/fdtdec.c b/lib/fdtdec.c index 17736ce665..125d9dbf26 100644 --- a/lib/fdtdec.c +++ b/lib/fdtdec.c @@ -242,7 +242,7 @@ int fdtdec_get_pci_bar32(struct udevice *dev, struct fdt_pci_addr *addr, uint64_t fdtdec_get_uint64(const void *blob, int node, const char *prop_name, uint64_t default_val) { - const uint64_t *cell64; + const unaligned_fdt64_t *cell64; int length;
cell64 = fdt_getprop(blob, node, prop_name, &length);