From: Yuri Tikhonov <yur@emcraft.com>
Date: Sat, 2 Feb 2008 07:47:31 +0000 (+0300)
Subject: [PPC] 8xx: swap bug-fix
X-Git-Tag: v2.6.25-rc6~30^2~14
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=1757f2d12dce775982aaa006bce1cf4f7ce90111;p=linux-2.6-omap-h63xx.git

[PPC] 8xx: swap bug-fix

This makes swap routines operate correctly on the ppc_8xx based machines.

Recent kernel's size makes swap feature very important on low-memory platfor
those are actually non-operable without it.

Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
---

diff --git a/arch/ppc/kernel/head_8xx.S b/arch/ppc/kernel/head_8xx.S
index eb8d26f8736..321bda2de2c 100644
--- a/arch/ppc/kernel/head_8xx.S
+++ b/arch/ppc/kernel/head_8xx.S
@@ -329,8 +329,18 @@ InstructionTLBMiss:
 	mfspr	r11, SPRN_MD_TWC	/* ....and get the pte address */
 	lwz	r10, 0(r11)	/* Get the pte */
 
+#ifdef CONFIG_SWAP
+	/* do not set the _PAGE_ACCESSED bit of a non-present page */
+	andi.	r11, r10, _PAGE_PRESENT
+	beq	4f
+	ori	r10, r10, _PAGE_ACCESSED
+	mfspr	r11, SPRN_MD_TWC	/* get the pte address again */
+	stw	r10, 0(r11)
+4:
+#else
 	ori	r10, r10, _PAGE_ACCESSED
 	stw	r10, 0(r11)
+#endif
 
 	/* The Linux PTE won't go exactly into the MMU TLB.
 	 * Software indicator bits 21, 22 and 28 must be clear.
@@ -395,8 +405,17 @@ DataStoreTLBMiss:
 	DO_8xx_CPU6(0x3b80, r3)
 	mtspr	SPRN_MD_TWC, r11
 
-	mfspr	r11, SPRN_MD_TWC	/* get the pte address again */
+#ifdef CONFIG_SWAP
+	/* do not set the _PAGE_ACCESSED bit of a non-present page */
+	andi.	r11, r10, _PAGE_PRESENT
+	beq	4f
+	ori	r10, r10, _PAGE_ACCESSED
+4:
+	/* and update pte in table */
+#else
 	ori	r10, r10, _PAGE_ACCESSED
+#endif
+	mfspr	r11, SPRN_MD_TWC	/* get the pte address again */
 	stw	r10, 0(r11)
 
 	/* The Linux PTE won't go exactly into the MMU TLB.
@@ -575,7 +594,16 @@ DataTLBError:
 
 	/* Update 'changed', among others.
 	*/
+#ifdef CONFIG_SWAP
+	ori	r10, r10, _PAGE_DIRTY|_PAGE_HWWRITE
+	/* do not set the _PAGE_ACCESSED bit of a non-present page */
+	andi.	r11, r10, _PAGE_PRESENT
+	beq	4f
+	ori	r10, r10, _PAGE_ACCESSED
+4:
+#else
 	ori	r10, r10, _PAGE_DIRTY|_PAGE_ACCESSED|_PAGE_HWWRITE
+#endif
 	mfspr	r11, SPRN_MD_TWC		/* Get pte address again */
 	stw	r10, 0(r11)		/* and update pte in table */
 
diff --git a/include/asm-ppc/pgtable.h b/include/asm-ppc/pgtable.h
index 69347bdbb40..70435d32129 100644
--- a/include/asm-ppc/pgtable.h
+++ b/include/asm-ppc/pgtable.h
@@ -299,14 +299,6 @@ extern unsigned long ioremap_bot, ioremap_base;
 #define _PMD_PAGE_MASK	0x000c
 #define _PMD_PAGE_8M	0x000c
 
-/*
- * The 8xx TLB miss handler allegedly sets _PAGE_ACCESSED in the PTE
- * for an address even if _PAGE_PRESENT is not set, as a performance
- * optimization.  This is a bug if you ever want to use swap unless
- * _PAGE_ACCESSED is 2, which it isn't, or unless you have 8xx-specific
- * definitions for __swp_entry etc. below, which would be gross.
- *  -- paulus
- */
 #define _PTE_NONE_MASK _PAGE_ACCESSED
 
 #else /* CONFIG_6xx */