Re: [PATCH] [v3] powerpc/4xx: work around CHIP11 errata in a more PAGE_SIZE-friendly way

[Hollis Blanchard <hollisb@us.ibm.com>]

On Tue, 2008-11-25 at 11:10 +1100, Michael Ellerman wrote:
> 
> Still, I think it would be better to only set memory_limit when the mem
> size is not a multiple of the PAGE_SIZE - so that memory_limit retains
> it's function as both the value of the limit and a boolean.

OK, how's this?

ppc: force memory size to be a multiple of PAGE_SIZE

Ensure that total memory size is page-aligned, because otherwise
mark_bootmem() gets upset.

This error case was triggered by using 64 KiB pages in the kernel while
arch/powerpc/boot/4xx.c arbitrarily reduced the amount of memory by 4096 (to
work around a chip bug that affects the last 256 bytes of physical memory).

Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -1160,6 +1160,8 @@ static inline void __init phyp_dump_rese
 
 void __init early_init_devtree(void *params)
 {
+	unsigned long limit;
+
 	DBG(" -> early_init_devtree(%p)\n", params);
 
 	/* Setup flat device-tree pointer */
@@ -1200,7 +1202,15 @@ void __init early_init_devtree(void *par
 	early_reserve_mem();
 	phyp_dump_reserve_mem();
 
-	lmb_enforce_memory_limit(memory_limit);
+	limit = memory_limit;
+	if (! limit) {
+		/* Ensure that total memory size is page-aligned, because
+		 * otherwise mark_bootmem() gets upset. */
+		lmb_analyze();
+		limit = lmb_phys_mem_size() & PAGE_MASK;
+	}
+	lmb_enforce_memory_limit(limit);
+
 	lmb_analyze();
 
 	DBG("Phys. mem: %lx\n", lmb_phys_mem_size());

-- 
Hollis Blanchard
IBM Linux Technology Center