xtensa: handle memmap kernel option

This option is useful for reserving memory regions for secondary cores
in AMP configurations.

Implement the following memmap variants:
- memmap=nn[KMG]@ss[KMG]: force usage of a specific region of memory;
- memmap=nn[KMG]$ss[KMG]: mark specified memory as reserved;
- memmap=nn[KMG]: set end of memory.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

2 files changed, 51 insertions, 0 deletions

diff --git a/arch/xtensa/kernel/setup.c b/arch/xtensa/kernel/setup.c
index 017c06aba9b2..9757bb74e532 100644
--- a/arch/xtensa/kernel/setup.c
+++ b/arch/xtensa/kernel/setup.c
@@ -507,6 +507,7 @@ void __init setup_arch(char **cmdline_p)
                     __pa(&_Level6InterruptVector_text_end), 0);
 #endif
 
+        parse_early_param();
         bootmem_init();
 
         unflatten_and_copy_device_tree();
diff --git a/arch/xtensa/mm/init.c b/arch/xtensa/mm/init.c
index 5d23697957bf..d70ba9333f44 100644
--- a/arch/xtensa/mm/init.c
+++ b/arch/xtensa/mm/init.c
@@ -332,3 +332,53 @@ void free_initmem(void)
 {
         free_initmem_default(-1);
 }
+
+static void __init parse_memmap_one(char *p)
+{
+        char *oldp;
+        unsigned long start_at, mem_size;
+
+        if (!p)
+                return;
+
+        oldp = p;
+        mem_size = memparse(p, &p);
+        if (p == oldp)
+                return;
+
+        switch (*p) {
+        case '@':
+                start_at = memparse(p + 1, &p);
+                add_sysmem_bank(start_at, start_at + mem_size);
+                break;
+
+        case '$':
+                start_at = memparse(p + 1, &p);
+                mem_reserve(start_at, start_at + mem_size, 0);
+                break;
+
+        case 0:
+                mem_reserve(mem_size, 0, 0);
+                break;
+
+        default:
+                pr_warn("Unrecognized memmap syntax: %s\n", p);
+                break;
+        }
+}
+
+static int __init parse_memmap_opt(char *str)
+{
+        while (str) {
+                char *k = strchr(str, ',');
+
+                if (k)
+                        *k++ = 0;
+
+                parse_memmap_one(str);
+                str = k;
+        }
+
+        return 0;
+}
+early_param("memmap", parse_memmap_opt);