MIPS: BCM47XX: Slightly clean memory detection
Patch was tested on devices with 64 MiB and 256 MiB of RAM.
It documents every part nicely and drops this hacky part of code:
max = off | ((128 << 20) - 1);
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Patchwork: https://patchwork.linux-mips.org/patch/6808/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/bcm47xx/prom.c b/arch/mips/bcm47xx/prom.c
index 0af808d..1a03a2f 100644
--- a/arch/mips/bcm47xx/prom.c
+++ b/arch/mips/bcm47xx/prom.c
@@ -69,15 +69,18 @@
* BCM47XX uses 128MB for addressing the ram, if the system contains
* less that that amount of ram it remaps the ram more often into the
* available space.
- * Accessing memory after 128MB will cause an exception.
- * max contains the biggest possible address supported by the platform.
- * If the method wants to try something above we assume 128MB ram.
*/
- off = (unsigned long)prom_init;
- max = off | ((128 << 20) - 1);
- for (mem = (1 << 20); mem < (128 << 20); mem += (1 << 20)) {
- if ((off + mem) > max) {
- mem = (128 << 20);
+
+ /* Physical address, without mapping to any kernel segment */
+ off = CPHYSADDR((unsigned long)prom_init);
+
+ /* Accessing memory after 128 MiB will cause an exception */
+ max = 128 << 20;
+
+ for (mem = 1 << 20; mem < max; mem += 1 << 20) {
+ /* Loop condition may be not enough, off may be over 1 MiB */
+ if (off + mem >= max) {
+ mem = max;
printk(KERN_DEBUG "assume 128MB RAM\n");
break;
}