efi: Add get_dram_base() helper function

Add the get_dram_base() function, shared by arm/arm64.

Signed-off-by: Roy Franz <roy.franz@linaro.org>
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/drivers/firmware/efi/efi-stub-helper.c b/drivers/firmware/efi/efi-stub-helper.c
index 1bf439be9138..a168dd20511f 100644
--- a/drivers/firmware/efi/efi-stub-helper.c
+++ b/drivers/firmware/efi/efi-stub-helper.c
@@ -11,6 +11,10 @@
  */
 #define EFI_READ_CHUNK_SIZE     (1024 * 1024)
 
+/* error code which can't be mistaken for valid address */
+#define EFI_ERROR       (~0UL)
+
+
 struct file_info {
         efi_file_handle_t *handle;
         u64 size;
@@ -83,6 +87,32 @@ fail:
         return status;
 }
 
+
+static unsigned long __init get_dram_base(efi_system_table_t *sys_table_arg)
+{
+        efi_status_t status;
+        unsigned long map_size;
+        unsigned long membase  = EFI_ERROR;
+        struct efi_memory_map map;
+        efi_memory_desc_t *md;
+
+        status = efi_get_memory_map(sys_table_arg, (efi_memory_desc_t **)&map.map,
+                                    &map_size, &map.desc_size, NULL, NULL);
+        if (status != EFI_SUCCESS)
+                return membase;
+
+        map.map_end = map.map + map_size;
+
+        for_each_efi_memory_desc(&map, md)
+                if (md->attribute & EFI_MEMORY_WB)
+                        if (membase > md->phys_addr)
+                                membase = md->phys_addr;
+
+        efi_call_early(free_pool, map.map);
+
+        return membase;
+}
+
 /*
  * Allocate at the highest possible address that is not above 'max'.
  */