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authorHauke Mehrtens <hauke@hauke-m.de>2010-07-27 16:12:43 -0400
committerRalf Baechle <ralf@linux-mips.org>2010-08-05 08:25:39 -0400
commitaec9222551353890190af810a4c93ed7050bfa19 (patch)
tree59a8fb2ac6f76807865e98f2b985575ecf56105f /arch/mips/bcm47xx
parent5c8974538afd97990d3730ef6fea731a34ef1f85 (diff)
MIPS: BCM47xx: Really fix 128MB RAM problem
The previous patch 4a86f2d27733f610e642649aca3e82e86fca9e22 (lmo) rsp. 84a6fcb368a080620d12fc4d79e07902dbee7335 (kernel.org) was wrong. The BCM47xx architecture maps the ram into a 128MB address space. It will be spaced there as often as goes into the 128MB. Detection tries to find the position where the same memory is found. When reading beyond 128MB the processor will throw an exception. If 128MB RAM is installed, it will not find a memory alias because it tries to read beyond the 128MB border. Now it just assumes 128MB installed ram if it can not find an alias. Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de> To: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/1508/ Acked-by: Florian Fainelli <florian@openwrt.org> Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/bcm47xx')
-rw-r--r--arch/mips/bcm47xx/prom.c22
1 files changed, 14 insertions, 8 deletions
diff --git a/arch/mips/bcm47xx/prom.c b/arch/mips/bcm47xx/prom.c
index 0fa646c5a84..f6e9063cc4c 100644
--- a/arch/mips/bcm47xx/prom.c
+++ b/arch/mips/bcm47xx/prom.c
@@ -126,6 +126,7 @@ static __init void prom_init_cmdline(void)
126static __init void prom_init_mem(void) 126static __init void prom_init_mem(void)
127{ 127{
128 unsigned long mem; 128 unsigned long mem;
129 unsigned long max;
129 130
130 /* Figure out memory size by finding aliases. 131 /* Figure out memory size by finding aliases.
131 * 132 *
@@ -134,21 +135,26 @@ static __init void prom_init_mem(void)
134 * want to reuse the memory used by CFE (around 4MB). That means cfe_* 135 * want to reuse the memory used by CFE (around 4MB). That means cfe_*
135 * functions stop to work at some point during the boot, we should only 136 * functions stop to work at some point during the boot, we should only
136 * call them at the beginning of the boot. 137 * call them at the beginning of the boot.
138 *
139 * BCM47XX uses 128MB for addressing the ram, if the system contains
140 * less that that amount of ram it remaps the ram more often into the
141 * available space.
142 * Accessing memory after 128MB will cause an exception.
143 * max contains the biggest possible address supported by the platform.
144 * If the method wants to try something above we assume 128MB ram.
137 */ 145 */
146 max = ((unsigned long)(prom_init) | ((128 << 20) - 1));
138 for (mem = (1 << 20); mem < (128 << 20); mem += (1 << 20)) { 147 for (mem = (1 << 20); mem < (128 << 20); mem += (1 << 20)) {
148 if (((unsigned long)(prom_init) + mem) > max) {
149 mem = (128 << 20);
150 printk(KERN_DEBUG "assume 128MB RAM\n");
151 break;
152 }
139 if (*(unsigned long *)((unsigned long)(prom_init) + mem) == 153 if (*(unsigned long *)((unsigned long)(prom_init) + mem) ==
140 *(unsigned long *)(prom_init)) 154 *(unsigned long *)(prom_init))
141 break; 155 break;
142 } 156 }
143 157
144 /* Ignoring the last page when ddr size is 128M. Cached
145 * accesses to last page is causing the processor to prefetch
146 * using address above 128M stepping out of the ddr address
147 * space.
148 */
149 if (mem == 0x8000000)
150 mem -= 0x1000;
151
152 add_memory_region(0, mem, BOOT_MEM_RAM); 158 add_memory_region(0, mem, BOOT_MEM_RAM);
153} 159}
154 160