[PATCH 2/8] ARM: mm: Introduce virt_to_idmap() with an arch hook

[Santosh Shilimkar]

On some PAE systems (e.g. TI Keystone), memory is above the
32-bit addressable limit, and the interconnect provides an
aliased view of parts of physical memory in the 32-bit addressable
space.  This alias is strictly for boot time usage, and is not
otherwise usable because of coherency limitations. On such systems,
the idmap mechanism needs to take this aliased mapping into account.

This patch introduces virt_to_idmap() and a arch function pointer which
can be populated by platform which needs it. Also populate necessary
idmap spots with now available virt_to_idmap(). Avoided #ifdef approach
to be compatible with multi-platform builds.

Most architecture won't touch it and in that case virt_to_idmap()
fall-back to existing virt_to_phys() macro.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar at ti.com>
---
 arch/arm/include/asm/memory.h |   16 ++++++++++++++++
 arch/arm/kernel/smp.c         |    2 +-
 arch/arm/mm/idmap.c           |    5 +++--
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index 93376e4..5944092 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -173,6 +173,7 @@
  */
 #define __PV_BITS_31_24	0x81000000
 
+extern phys_addr_t (*arch_virt_to_idmap) (unsigned long x);
 extern unsigned long __pv_phys_offset;
 #define PHYS_OFFSET __pv_phys_offset
 
@@ -259,6 +260,21 @@ static inline void *phys_to_virt(phys_addr_t x)
 #define pfn_to_kaddr(pfn)	__va((pfn) << PAGE_SHIFT)
 
 /*
+ * These are for systems that have a hardware interconnect supported alias of
+ * physical memory for idmap purposes.  Most cases should leave these
+ * untouched.
+ */
+static inline phys_addr_t __virt_to_idmap(unsigned long x)
+{
+	if (arch_virt_to_idmap)
+		return arch_virt_to_idmap(x);
+	else
+		return __virt_to_phys(x);
+}
+
+#define virt_to_idmap(x)	__virt_to_idmap((unsigned long)(x))
+
+/*
  * Virtual <-> DMA view memory address translations
  * Again, these are *only* valid on the kernel direct mapped RAM
  * memory.  Use of these is *deprecated* (and that doesn't mean
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 217b755..e1a7b9a 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -80,7 +80,7 @@ void __init smp_set_ops(struct smp_operations *ops)
 
 static unsigned long get_arch_pgd(pgd_t *pgd)
 {
-	phys_addr_t pgdir = virt_to_phys(pgd);
+	phys_addr_t pgdir = virt_to_idmap(pgd);
 	BUG_ON(pgdir & ARCH_PGD_MASK);
 	return pgdir >> ARCH_PGD_SHIFT;
 }
diff --git a/arch/arm/mm/idmap.c b/arch/arm/mm/idmap.c
index 83cb3ac..c0a1e48 100644
--- a/arch/arm/mm/idmap.c
+++ b/arch/arm/mm/idmap.c
@@ -10,6 +10,7 @@
 #include <asm/system_info.h>
 
 pgd_t *idmap_pgd;
+phys_addr_t (*arch_virt_to_idmap) (unsigned long x);
 
 #ifdef CONFIG_ARM_LPAE
 static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
@@ -67,8 +68,8 @@ static void identity_mapping_add(pgd_t *pgd, const char *text_start,
 	unsigned long addr, end;
 	unsigned long next;
 
-	addr = virt_to_phys(text_start);
-	end = virt_to_phys(text_end);
+	addr = virt_to_idmap(text_start);
+	end = virt_to_idmap(text_end);
 
 	prot |= PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_AF;
 
-- 
1.7.9.5