of/fdt: make memblock minimum physical address arch configurable

By default, early_init_dt_add_memory_arch() ignores memory below
the base of the kernel image since it won't be addressable via the
linear mapping. However, this is not appropriate anymore once we
decouple the kernel text mapping from the linear mapping, so archs
may want to drop the low limit entirely. So allow the minimum to be
overridden by setting MIN_MEMBLOCK_ADDR.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 270522a04f7a9911983878fa37da467f9ff1c938)
Signed-off-by: Alex Shi <alex.shi@linaro.org>

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 655f79db7899ffd0628714d51203847630a8075c..1f98156f8996401f525eedbfde2053d9cd95f807 100644 (file)
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -976,13 +976,16 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
 }
 
 #ifdef CONFIG_HAVE_MEMBLOCK
+#ifndef MIN_MEMBLOCK_ADDR
+#define MIN_MEMBLOCK_ADDR      __pa(PAGE_OFFSET)
+#endif
 #ifndef MAX_MEMBLOCK_ADDR
 #define MAX_MEMBLOCK_ADDR      ((phys_addr_t)~0)
 #endif
 
 void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
 {
-       const u64 phys_offset = __pa(PAGE_OFFSET);
+       const u64 phys_offset = MIN_MEMBLOCK_ADDR;
 
        if (!PAGE_ALIGNED(base)) {
                if (size < PAGE_SIZE - (base & ~PAGE_MASK)) {