[PATCH V6] ARM: LPAE: Fix mapping in alloc_init_section for unaligned addresses

[R Sricharan]

With LPAE enabled, alloc_init_section() does not map the entire
address space for unaligned addresses.

The issue also reproduced with CMA + LPAE. CMA tries to map 16MB
with page granularity mappings during boot. alloc_init_pte()
is called and out of 16MB, only 2MB gets mapped and rest remains
unaccessible.

Because of this OMAP5 boot is broken with CMA + LPAE enabled.
Fix the issue by ensuring that the entire addresses are
mapped.

Signed-off-by: R Sricharan <r.sricharan at ti.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Christoffer Dall <chris at cloudcar.com>
Cc: Russell King <linux at arm.linux.org.uk>
Cc: Santosh Shilimkar <santosh.shilimkar at ti.com>
---
 [V2] Moved the loop to alloc_init_pte as per Russell's
     feedback and changed the subject accordingly.
     Using PMD_XXX instead of SECTION_XXX to avoid
     different loop increments with/without LPAE.

 [v3] Removed the dummy variable phys and updated
      the commit log for CMA case.

 [v4] Resending with updated change log and
      updating the tags.

 [v5] Renamed alloc_init_section to alloc_init_pmd
      and moved the loop back there. Also introduced
      map_init_section as per Catalin's comments.

 [v6] Corrected tags and updated the comments for code.

 arch/arm/mm/mmu.c |   73 ++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 47 insertions(+), 26 deletions(-)

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index ce328c7..73aebcb 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -576,39 +576,60 @@ static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr,
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 }
 
-static void __init alloc_init_section(pud_t *pud, unsigned long addr,
-				      unsigned long end, phys_addr_t phys,
-				      const struct mem_type *type)
+static void __init map_init_section(pmd_t *pmd, unsigned long addr,
+			unsigned long end, phys_addr_t phys,
+			const struct mem_type *type)
 {
-	pmd_t *pmd = pmd_offset(pud, addr);
-
+#ifndef CONFIG_ARM_LPAE
 	/*
-	 * Try a section mapping - end, addr and phys must all be aligned
-	 * to a section boundary.  Note that PMDs refer to the individual
-	 * L1 entries, whereas PGDs refer to a group of L1 entries making
-	 * up one logical pointer to an L2 table.
+	 * In classic MMU format, puds and pmds are folded in to
+	 * the pgds. pmd_offset gives the PGD entry. PGDs refer to a
+	 * group of L1 entries making up one logical pointer to
+	 * an L2 table (2MB), where as PMDs refer to the individual
+	 * L1 entries (1MB). Hence increment to get the correct
+	 * offset for odd 1MB sections.
+	 * (See arch/arm/include/asm/pgtable-2level.h)
 	 */
-	if (type->prot_sect && ((addr | end | phys) & ~SECTION_MASK) == 0) {
-		pmd_t *p = pmd;
-
-#ifndef CONFIG_ARM_LPAE
-		if (addr & SECTION_SIZE)
-			pmd++;
+	if (addr & SECTION_SIZE)
+		pmd++;
 #endif
+	do {
+		*pmd = __pmd(phys | type->prot_sect);
+		phys += SECTION_SIZE;
+	} while (pmd++, addr += SECTION_SIZE, addr != end);
 
-		do {
-			*pmd = __pmd(phys | type->prot_sect);
-			phys += SECTION_SIZE;
-		} while (pmd++, addr += SECTION_SIZE, addr != end);
+	flush_pmd_entry(pmd);
+}
 
-		flush_pmd_entry(p);
-	} else {
+static void __init alloc_init_pmd(pud_t *pud, unsigned long addr,
+				      unsigned long end, phys_addr_t phys,
+				      const struct mem_type *type)
+{
+	pmd_t *pmd = pmd_offset(pud, addr);
+	unsigned long next;
+
+	do {
 		/*
-		 * No need to loop; pte's aren't interested in the
-		 * individual L1 entries.
+		 * With LPAE, we must loop over to map
+		 * all the pmds for the given range.
 		 */
-		alloc_init_pte(pmd, addr, end, __phys_to_pfn(phys), type);
-	}
+		next = pmd_addr_end(addr, end);
+
+		/*
+		 * Try a section mapping - end, addr and phys must all be
+		 * aligned to a section boundary.
+		 */
+		if (type->prot_sect &&
+				((addr | next | phys) & ~SECTION_MASK) == 0) {
+			map_init_section(pmd, addr, next, phys, type);
+		} else {
+			alloc_init_pte(pmd, addr, next,
+						__phys_to_pfn(phys), type);
+		}
+
+		phys += next - addr;
+
+	} while (pmd++, addr = next, addr != end);
 }
 
 static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
@@ -619,7 +640,7 @@ static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
 
 	do {
 		next = pud_addr_end(addr, end);
-		alloc_init_section(pud, addr, next, phys, type);
+		alloc_init_pmd(pud, addr, next, phys, type);
 		phys += next - addr;
 	} while (pud++, addr = next, addr != end);
 }
-- 
1.7.9.5