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67 lines
2.4 KiB
Diff
67 lines
2.4 KiB
Diff
From bf93090747e3d23e5354bd8da52f85d96c0f6606 Mon Sep 17 00:00:00 2001
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From: Hauke Mehrtens <hauke@hauke-m.de>
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Date: Sun, 18 Jul 2010 12:49:41 +0200
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Subject: [PATCH 1/5] MIPS: BCM47xx: Really fix 128MB RAM problem
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The previews patch 84a6fcb368a080620d12fc4d79e07902dbee7335 was wrong,
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I got wrong success reports.
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The bcm47xx architecture maps the ram into a 128MB address space. It
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will be paced there as often as goes into the 128MB. The detection
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tries to find the position where the same memory is found. When reading
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over 128MB the processor will throw an exception. If 128MB ram is
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installed, it will not find the same memory because it tries to read
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over the 128MB boarder. Now it just assumes 128MB installed ram if it
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can not find that the ram is repeating.
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Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
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---
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arch/mips/bcm47xx/prom.c | 22 ++++++++++++++--------
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1 files changed, 14 insertions(+), 8 deletions(-)
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--- a/arch/mips/bcm47xx/prom.c
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+++ b/arch/mips/bcm47xx/prom.c
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@@ -126,6 +126,7 @@ static __init void prom_init_cmdline(voi
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static __init void prom_init_mem(void)
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{
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unsigned long mem;
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+ unsigned long max;
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/* Figure out memory size by finding aliases.
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*
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@@ -134,21 +135,26 @@ static __init void prom_init_mem(void)
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* want to reuse the memory used by CFE (around 4MB). That means cfe_*
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* functions stop to work at some point during the boot, we should only
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* call them at the beginning of the boot.
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+ *
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+ * BCM47XX uses 128MB for addressing the ram, if the system contains
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+ * less that that amount of ram it remaps the ram more often into the
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+ * available space.
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+ * Accessing memory after 128MB will cause an exception.
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+ * max contains the biggest possible address supported by the platform.
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+ * If the method wants to try something above we assume 128MB ram.
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*/
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+ max = ((unsigned long)(prom_init) | ((128 << 20) - 1));
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for (mem = (1 << 20); mem < (128 << 20); mem += (1 << 20)) {
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+ if (((unsigned long)(prom_init) + mem) > max) {
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+ mem = (128 << 20);
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+ printk(KERN_DEBUG "assume 128MB RAM\n");
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+ break;
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+ }
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if (*(unsigned long *)((unsigned long)(prom_init) + mem) ==
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*(unsigned long *)(prom_init))
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break;
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}
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- /* Ignoring the last page when ddr size is 128M. Cached
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- * accesses to last page is causing the processor to prefetch
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- * using address above 128M stepping out of the ddr address
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- * space.
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- */
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- if (mem == 0x8000000)
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- mem -= 0x1000;
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-
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add_memory_region(0, mem, BOOT_MEM_RAM);
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}
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