linux-mips
[Top] [All Lists]

Re: [PATCH 2/5] MIPS: BCM47XX: improve memory size detection

To: linux-mips@linux-mips.org
Subject: Re: [PATCH 2/5] MIPS: BCM47XX: improve memory size detection
From: John Crispin <john@phrozen.org>
Date: Tue, 02 Oct 2012 09:18:18 +0200
In-reply-to: <1348942326-27195-3-git-send-email-hauke@hauke-m.de>
List-archive: <http://www.linux-mips.org/archives/linux-mips/>
List-help: <mailto:ecartis@linux-mips.org?Subject=help>
List-id: linux-mips <linux-mips.eddie.linux-mips.org>
List-owner: <mailto:ralf@linux-mips.org>
List-post: <mailto:linux-mips@linux-mips.org>
List-software: Ecartis version 1.0.0
List-subscribe: <mailto:ecartis@linux-mips.org?subject=subscribe%20linux-mips>
List-unsubscribe: <mailto:ecartis@linux-mips.org?subject=unsubscribe%20linux-mips>
References: <1348942326-27195-1-git-send-email-hauke@hauke-m.de> <1348942326-27195-3-git-send-email-hauke@hauke-m.de>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.6esrpre) Gecko/20120817 Icedove/10.0.6
On 29/09/12 20:12, Hauke Mehrtens wrote:
The memory size is detected by finding a place where it repeats in
memory. Currently we are just checking when the function prom_init is
seen again, but with this patch it also checks some more bytes.

This should fix a problem we saw in OpenWrt, where the detected
available memory decreased on some devices when doing a soft reboot.

Signed-off-by: Hauke Mehrtens<hauke@hauke-m.de>
---
  arch/mips/bcm47xx/prom.c |   14 ++++++++++----
  1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/mips/bcm47xx/prom.c b/arch/mips/bcm47xx/prom.c
index 22258a4..c18f59a 100644
--- a/arch/mips/bcm47xx/prom.c
+++ b/arch/mips/bcm47xx/prom.c
@@ -1,6 +1,7 @@
  /*
   *  Copyright (C) 2004 Florian Schirmer<jolt@tuxbox.org>
   *  Copyright (C) 2007 Aurelien Jarno<aurelien@aurel32.net>
+ *  Copyright (C) 2010-2012 Hauke Mehrtens<hauke@hauke-m.de>
   *
   *  This program is free software; you can redistribute  it and/or modify it
   *  under  the terms of  the GNU General  Public License as published by the
@@ -128,6 +129,7 @@ static __init void prom_init_mem(void)
  {
        unsigned long mem;
        unsigned long max;
+       unsigned long off, data, off1, data1;
        struct cpuinfo_mips *c =&current_cpu_data;

        /* Figure out memory size by finding aliases.
@@ -145,15 +147,19 @@ static __init void prom_init_mem(void)
         * max contains the biggest possible address supported by the platform.
         * If the method wants to try something above we assume 128MB ram.
         */
-       max = ((unsigned long)(prom_init) | ((128<<  20) - 1));
+       off = (unsigned long)prom_init;
+       data = *(unsigned long *)prom_init;
+       off1 = off + 4;
+       data1 = *(unsigned long *)off1;
+       max = off | ((128<<  20) - 1);
        for (mem = (1<<  20); mem<  (128<<  20); mem += (1<<  20)) {
-               if (((unsigned long)(prom_init) + mem)>  max) {
+               if ((off + mem)>  max) {
                        mem = (128<<  20);
                        printk(KERN_DEBUG "assume 128MB RAM\n");
                        break;
                }
-               if (*(unsigned long *)((unsigned long)(prom_init) + mem) ==
-                   *(unsigned long *)(prom_init))
+               if ((*(unsigned long *)(off + mem) == data)&&
+                       (*(unsigned long *)(off1 + mem) == data1))
                        break;
        }


Hi Hauke,

somehow i have the feeling, that using memcmp() should be used here instead of comparing memory by hand.

        John

<Prev in Thread] Current Thread [Next in Thread>
  • Re: [PATCH 2/5] MIPS: BCM47XX: improve memory size detection, John Crispin <=