powerpc/8xx: Make pinning of ITLBs optional

As stated in a comment in head_8xx.S, today we "Always pin the first
8 MB ITLB to prevent ITLB misses while mucking around with SRR0/SRR1
in asm".

This issue has just been cleared by the preceding patch, therefore
we can make this pinning optional (on by default) and independent
of DATA pinning.

This patch also makes pinning of IMMR independent of pinning of DATA.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 45 insertions, 12 deletions

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 35058661288f..ef4c96bd3409 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -55,6 +55,15 @@
 #define SIMPLE_KERNEL_ADDRESS		1
 #endif
 
+/*
+ * We need an ITLB miss handler for kernel addresses if:
+ * - Either we have modules
+ * - Or we have not pinned the first 8M
+ */
+#if defined(CONFIG_MODULES) || !defined(CONFIG_PIN_TLB_TEXT) || \
+    defined(CONFIG_DEBUG_PAGEALLOC)
+#define ITLB_MISS_KERNEL	1
+#endif
 
 /*
  * Value for the bits that have fixed value in RPN entries.
@@ -317,7 +326,7 @@ SystemCall:
 #endif
 
 InstructionTLBMiss:
-#if defined(CONFIG_8xx_CPU6) || defined(CONFIG_MODULES) || defined (CONFIG_DEBUG_PAGEALLOC) || defined (CONFIG_HUGETLB_PAGE)
+#if defined(CONFIG_8xx_CPU6) || defined(ITLB_MISS_KERNEL) || defined(CONFIG_HUGETLB_PAGE)
 	mtspr	SPRN_SPRG_SCRATCH2, r3
 #endif
 	EXCEPTION_PROLOG_0
@@ -335,24 +344,32 @@ InstructionTLBMiss:
 	INVALIDATE_ADJACENT_PAGES_CPU15(r11, r10)
 	/* Only modules will cause ITLB Misses as we always
 	 * pin the first 8MB of kernel memory */
-#if defined(CONFIG_MODULES) || defined (CONFIG_DEBUG_PAGEALLOC) || defined (CONFIG_HUGETLB_PAGE)
+#if defined(ITLB_MISS_KERNEL) || defined(CONFIG_HUGETLB_PAGE)
 	mfcr	r3
 #endif
-#if defined(CONFIG_MODULES) || defined (CONFIG_DEBUG_PAGEALLOC)
-#ifdef SIMPLE_KERNEL_ADDRESS
+#ifdef ITLB_MISS_KERNEL
+#if defined(SIMPLE_KERNEL_ADDRESS) && defined(CONFIG_PIN_TLB_TEXT)
 	andis.	r11, r10, 0x8000	/* Address >= 0x80000000 */
 #else
 	rlwinm	r11, r10, 16, 0xfff8
 	cmpli	cr0, r11, PAGE_OFFSET@h
+#ifndef CONFIG_PIN_TLB_TEXT
+	/* It is assumed that kernel code fits into the first 8M page */
+_ENTRY(ITLBMiss_cmp)
+	cmpli	cr7, r11, (PAGE_OFFSET + 0x0800000)@h
+#endif
 #endif
 #endif
 	mfspr	r11, SPRN_M_TW	/* Get level 1 table */
-#if defined(CONFIG_MODULES) || defined (CONFIG_DEBUG_PAGEALLOC)
-#ifdef SIMPLE_KERNEL_ADDRESS
+#ifdef ITLB_MISS_KERNEL
+#if defined(SIMPLE_KERNEL_ADDRESS) && defined(CONFIG_PIN_TLB_TEXT)
 	beq+	3f
 #else
 	blt+	3f
 #endif
+#ifndef CONFIG_PIN_TLB_TEXT
+	blt	cr7, ITLBMissLinear
+#endif
 	lis	r11, (swapper_pg_dir-PAGE_OFFSET)@ha
 3:
 #endif
@@ -370,7 +387,7 @@ InstructionTLBMiss:
 	rlwimi	r10, r11, 0, 0, 32 - PAGE_SHIFT - 1	/* Add level 2 base */
 	lwz	r10, 0(r10)	/* Get the pte */
 4:
-#if defined(CONFIG_MODULES) || defined (CONFIG_DEBUG_PAGEALLOC) || defined (CONFIG_HUGETLB_PAGE)
+#if defined(ITLB_MISS_KERNEL) || defined(CONFIG_HUGETLB_PAGE)
 	mtcr	r3
 #endif
 	/* Insert the APG into the TWC from the Linux PTE. */
@@ -401,7 +418,7 @@ InstructionTLBMiss:
 	MTSPR_CPU6(SPRN_MI_RPN, r10, r3)	/* Update TLB entry */
 
 	/* Restore registers */
-#if defined(CONFIG_8xx_CPU6) || defined(CONFIG_MODULES) || defined (CONFIG_DEBUG_PAGEALLOC) || defined (CONFIG_HUGETLB_PAGE)
+#if defined(CONFIG_8xx_CPU6) || defined(ITLB_MISS_KERNEL) || defined(CONFIG_HUGETLB_PAGE)
 	mfspr	r3, SPRN_SPRG_SCRATCH2
 #endif
 	EXCEPTION_EPILOG_0
@@ -696,6 +713,22 @@ DTLBMissLinear:
 	EXCEPTION_EPILOG_0
 	rfi
 
+#ifndef CONFIG_PIN_TLB_TEXT
+ITLBMissLinear:
+	mtcr	r3
+	/* Set 8M byte page and mark it valid */
+	li	r11, MI_PS8MEG | MI_SVALID | _PAGE_EXEC
+	MTSPR_CPU6(SPRN_MI_TWC, r11, r3)
+	rlwinm	r10, r10, 0, 0x0f800000	/* 8xx supports max 256Mb RAM */
+	ori	r10, r10, 0xf0 | MI_SPS16K | _PAGE_SHARED | _PAGE_DIRTY	| \
+			  _PAGE_PRESENT
+	MTSPR_CPU6(SPRN_MI_RPN, r10, r11)	/* Update TLB entry */
+
+	mfspr	r3, SPRN_SPRG_SCRATCH2
+	EXCEPTION_EPILOG_0
+	rfi
+#endif
+
 /* This is the procedure to calculate the data EA for buggy dcbx,dcbi instructions
  * by decoding the registers used by the dcbx instruction and adding them.
  * DAR is set to the calculated address.
@@ -955,15 +988,14 @@ initial_mmu:
 	mtspr	SPRN_MD_CTR, r10	/* remove PINNED DTLB entries */
 
 	tlbia			/* Invalidate all TLB entries */
-/* Always pin the first 8 MB ITLB to prevent ITLB
-   misses while mucking around with SRR0/SRR1 in asm
-*/
+#ifdef CONFIG_PIN_TLB_TEXT
 	lis	r8, MI_RSV4I@h
 	ori	r8, r8, 0x1c00
 
 	mtspr	SPRN_MI_CTR, r8	/* Set instruction MMU control */
+#endif
 
-#ifdef CONFIG_PIN_TLB
+#ifdef CONFIG_PIN_TLB_DATA
 	oris	r10, r10, MD_RSV4I@h
 	mtspr	SPRN_MD_CTR, r10	/* Set data TLB control */
 #endif
@@ -989,6 +1021,7 @@ initial_mmu:
 	 * internal registers (among other things).
 	 */
 #ifdef CONFIG_PIN_TLB_IMMR
+	oris	r10, r10, MD_RSV4I@h
 	ori	r10, r10, 0x1c00
 	mtspr	SPRN_MD_CTR, r10