powerpc/e6500: TLB miss handler with hardware tablewalk support

There are a few things that make the existing hw tablewalk handlers
unsuitable for e6500:

 - Indirect entries go in TLB1 (though the resulting direct entries go in
   TLB0).

 - It has threads, but no "tlbsrx." -- so we need a spinlock and
   a normal "tlbsx".  Because we need this lock, hardware tablewalk
   is mandatory on e6500 unless we want to add spinlock+tlbsx to
   the normal bolted TLB miss handler.

 - TLB1 has no HES (nor next-victim hint) so we need software round robin
   (TODO: integrate this round robin data with hugetlb/KVM)

 - The existing tablewalk handlers map half of a page table at a time,
   because IBM hardware has a fixed 1MiB indirect page size.  e6500
   has variable size indirect entries, with a minimum of 2MiB.
   So we can't do the half-page indirect mapping, and even if we
   could it would be less efficient than mapping the full page.

 - Like on e5500, the linear mapping is bolted, so we don't need the
   overhead of supporting nested tlb misses.

Note that hardware tablewalk does not work in rev1 of e6500.
We do not expect to support e6500 rev1 in mainline Linux.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Cc: Mihai Caraman <mihai.caraman@freescale.com>

1 files changed, 67 insertions, 26 deletions

diff --git a/arch/powerpc/mm/tlb_nohash.c b/arch/powerpc/mm/tlb_nohash.c
index 8805b7b..735839b 100644
--- a/arch/powerpc/mm/tlb_nohash.c
+++ b/arch/powerpc/mm/tlb_nohash.c
@@ -43,6 +43,7 @@
 #include <asm/tlb.h>
 #include <asm/code-patching.h>
 #include <asm/hugetlb.h>
+#include <asm/paca.h>
 
 #include "mmu_decl.h"
 
@@ -58,6 +59,10 @@ struct mmu_psize_def mmu_psize_defs[MMU_PAGE_COUNT] = {
 		.shift	= 12,
 		.enc	= BOOK3E_PAGESZ_4K,
 	},
+	[MMU_PAGE_2M] = {
+		.shift	= 21,
+		.enc	= BOOK3E_PAGESZ_2M,
+	},
 	[MMU_PAGE_4M] = {
 		.shift	= 22,
 		.enc	= BOOK3E_PAGESZ_4M,
@@ -136,7 +141,7 @@ static inline int mmu_get_tsize(int psize)
 int mmu_linear_psize;		/* Page size used for the linear mapping */
 int mmu_pte_psize;		/* Page size used for PTE pages */
 int mmu_vmemmap_psize;		/* Page size used for the virtual mem map */
-int book3e_htw_enabled;		/* Is HW tablewalk enabled ? */
+int book3e_htw_mode;		/* HW tablewalk?  Value is PPC_HTW_* */
 unsigned long linear_map_top;	/* Top of linear mapping */
 
 #endif /* CONFIG_PPC64 */
@@ -377,7 +382,7 @@ void tlb_flush_pgtable(struct mmu_gather *tlb, unsigned long address)
 {
 	int tsize = mmu_psize_defs[mmu_pte_psize].enc;
 
-	if (book3e_htw_enabled) {
+	if (book3e_htw_mode != PPC_HTW_NONE) {
 		unsigned long start = address & PMD_MASK;
 		unsigned long end = address + PMD_SIZE;
 		unsigned long size = 1UL << mmu_psize_defs[mmu_pte_psize].shift;
@@ -430,7 +435,7 @@ static void setup_page_sizes(void)
 			def = &mmu_psize_defs[psize];
 			shift = def->shift;
 
-			if (shift == 0)
+			if (shift == 0 || shift & 1)
 				continue;
 
 			/* adjust to be in terms of 4^shift Kb */
@@ -440,21 +445,40 @@ static void setup_page_sizes(void)
 				def->flags |= MMU_PAGE_SIZE_DIRECT;
 		}
 
-		goto no_indirect;
+		goto out;
 	}
 
 	if (fsl_mmu && (mmucfg & MMUCFG_MAVN) == MMUCFG_MAVN_V2) {
-		u32 tlb1ps = mfspr(SPRN_TLB1PS);
+		u32 tlb1cfg, tlb1ps;
+
+		tlb0cfg = mfspr(SPRN_TLB0CFG);
+		tlb1cfg = mfspr(SPRN_TLB1CFG);
+		tlb1ps = mfspr(SPRN_TLB1PS);
+		eptcfg = mfspr(SPRN_EPTCFG);
+
+		if ((tlb1cfg & TLBnCFG_IND) && (tlb0cfg & TLBnCFG_PT))
+			book3e_htw_mode = PPC_HTW_E6500;
+
+		/*
+		 * We expect 4K subpage size and unrestricted indirect size.
+		 * The lack of a restriction on indirect size is a Freescale
+		 * extension, indicated by PSn = 0 but SPSn != 0.
+		 */
+		if (eptcfg != 2)
+			book3e_htw_mode = PPC_HTW_NONE;
 
 		for (psize = 0; psize < MMU_PAGE_COUNT; ++psize) {
 			struct mmu_psize_def *def = &mmu_psize_defs[psize];
 
 			if (tlb1ps & (1U << (def->shift - 10))) {
 				def->flags |= MMU_PAGE_SIZE_DIRECT;
+
+				if (book3e_htw_mode && psize == MMU_PAGE_2M)
+					def->flags |= MMU_PAGE_SIZE_INDIRECT;
 			}
 		}
 
-		goto no_indirect;
+		goto out;
 	}
 #endif
 
@@ -471,8 +495,11 @@ static void setup_page_sizes(void)
 	}
 
 	/* Indirect page sizes supported ? */
-	if ((tlb0cfg & TLBnCFG_IND) == 0)
-		goto no_indirect;
+	if ((tlb0cfg & TLBnCFG_IND) == 0 ||
+	    (tlb0cfg & TLBnCFG_PT) == 0)
+		goto out;
+
+	book3e_htw_mode = PPC_HTW_IBM;
 
 	/* Now, we only deal with one IND page size for each
 	 * direct size. Hopefully all implementations today are
@@ -497,8 +524,8 @@ static void setup_page_sizes(void)
 				def->ind = ps + 10;
 		}
 	}
- no_indirect:
 
+out:
 	/* Cleanup array and print summary */
 	pr_info("MMU: Supported page sizes\n");
 	for (psize = 0; psize < MMU_PAGE_COUNT; ++psize) {
@@ -520,23 +547,23 @@ static void setup_page_sizes(void)
 
 static void setup_mmu_htw(void)
 {
-	/* Check if HW tablewalk is present, and if yes, enable it by:
-	 *
-	 * - patching the TLB miss handlers to branch to the
-	 *   one dedicates to it
-	 *
-	 * - setting the global book3e_htw_enabled
-       	 */
-	unsigned int tlb0cfg = mfspr(SPRN_TLB0CFG);
+	/*
+	 * If we want to use HW tablewalk, enable it by patching the TLB miss
+	 * handlers to branch to the one dedicated to it.
+	 */
 
-	if ((tlb0cfg & TLBnCFG_IND) &&
-	    (tlb0cfg & TLBnCFG_PT)) {
+	switch (book3e_htw_mode) {
+	case PPC_HTW_IBM:
 		patch_exception(0x1c0, exc_data_tlb_miss_htw_book3e);
 		patch_exception(0x1e0, exc_instruction_tlb_miss_htw_book3e);
-		book3e_htw_enabled = 1;
+		break;
+	case PPC_HTW_E6500:
+		patch_exception(0x1c0, exc_data_tlb_miss_e6500_book3e);
+		patch_exception(0x1e0, exc_instruction_tlb_miss_e6500_book3e);
+		break;
 	}
 	pr_info("MMU: Book3E HW tablewalk %s\n",
-		book3e_htw_enabled ? "enabled" : "not supported");
+		book3e_htw_mode != PPC_HTW_NONE ? "enabled" : "not supported");
 }
 
 /*
@@ -576,8 +603,16 @@ static void __early_init_mmu(int boot_cpu)
 	/* Set MAS4 based on page table setting */
 
 	mas4 = 0x4 << MAS4_WIMGED_SHIFT;
-	if (book3e_htw_enabled) {
-		mas4 |= mas4 | MAS4_INDD;
+	switch (book3e_htw_mode) {
+	case PPC_HTW_E6500:
+		mas4 |= MAS4_INDD;
+		mas4 |= BOOK3E_PAGESZ_2M << MAS4_TSIZED_SHIFT;
+		mas4 |= MAS4_TLBSELD(1);
+		mmu_pte_psize = MMU_PAGE_2M;
+		break;
+
+	case PPC_HTW_IBM:
+		mas4 |= MAS4_INDD;
 #ifdef CONFIG_PPC_64K_PAGES
 		mas4 |=	BOOK3E_PAGESZ_256M << MAS4_TSIZED_SHIFT;
 		mmu_pte_psize = MMU_PAGE_256M;
@@ -585,13 +620,16 @@ static void __early_init_mmu(int boot_cpu)
 		mas4 |=	BOOK3E_PAGESZ_1M << MAS4_TSIZED_SHIFT;
 		mmu_pte_psize = MMU_PAGE_1M;
 #endif
-	} else {
+		break;
+
+	case PPC_HTW_NONE:
 #ifdef CONFIG_PPC_64K_PAGES
 		mas4 |=	BOOK3E_PAGESZ_64K << MAS4_TSIZED_SHIFT;
 #else
 		mas4 |=	BOOK3E_PAGESZ_4K << MAS4_TSIZED_SHIFT;
 #endif
 		mmu_pte_psize = mmu_virtual_psize;
+		break;
 	}
 	mtspr(SPRN_MAS4, mas4);
 
@@ -611,8 +649,11 @@ static void __early_init_mmu(int boot_cpu)
 		/* limit memory so we dont have linear faults */
 		memblock_enforce_memory_limit(linear_map_top);
 
-		patch_exception(0x1c0, exc_data_tlb_miss_bolted_book3e);
-		patch_exception(0x1e0, exc_instruction_tlb_miss_bolted_book3e);
+		if (book3e_htw_mode == PPC_HTW_NONE) {
+			patch_exception(0x1c0, exc_data_tlb_miss_bolted_book3e);
+			patch_exception(0x1e0,
+				exc_instruction_tlb_miss_bolted_book3e);
+		}
 	}
 #endif