[PATCH] ARM: expand fixmap region to 3MB

[Rob Herring]

From: Rob Herring <robh at kernel.org>

With commit a05e54c103b0b8 "ARM: 8031/2: change fixmap mapping region to
support 32 CPUs", the fixmap region was expanded to 2MB, but it
precluded any other uses of the fixmap region in order to support up to
32 CPUs. In order to support other uses the fixmap region needs to be
expanded beyond 2MB. Fortunately, the adjacent 1MB range
0xffe00000-0xfff00000 is availabe to use.

Remove fixmap_page_table ptr and lookup the page table via the virtual
address so that the fixmap region can span more that one pmd. The 2nd
pmd is already created since it is shared with the vector page.

Cc: Leif Lindholm <leif.lindholm at linaro.org>
Cc: Kees Cook <keescook at chromium.org>
Cc: Russell King <linux at arm.linux.org.uk>
Signed-off-by: Rob Herring <robh at kernel.org>
---

This patch can come before or after the generic fixmap.h. There's a 
single line conflict with the ending address 

This worked for earlycon, but I've not done any highmem specific 
testing. My full series is available here:

git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git fixmap

Rob

 Documentation/arm/memory.txt  |  2 +-
 arch/arm/include/asm/fixmap.h |  2 +-
 arch/arm/mm/highmem.c         | 15 ++++++++-------
 arch/arm/mm/mmu.c             |  2 +-
 4 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/Documentation/arm/memory.txt b/Documentation/arm/memory.txt
index 38dc06d..4178ebd 100644
--- a/Documentation/arm/memory.txt
+++ b/Documentation/arm/memory.txt
@@ -41,7 +41,7 @@ fffe8000	fffeffff	DTCM mapping area for platforms with
 fffe0000	fffe7fff	ITCM mapping area for platforms with
 				ITCM mounted inside the CPU.
 
-ffc00000	ffdfffff	Fixmap mapping region.  Addresses provided
+ffc00000	ffefffff	Fixmap mapping region.  Addresses provided
 				by fix_to_virt() will be located here.
 
 fee00000	feffffff	Mapping of PCI I/O space. This is a static
diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
index 74124b0..cb50cee 100644
--- a/arch/arm/include/asm/fixmap.h
+++ b/arch/arm/include/asm/fixmap.h
@@ -2,7 +2,7 @@
 #define _ASM_FIXMAP_H
 
 #define FIXADDR_START		0xffc00000UL
-#define FIXADDR_TOP		0xffe00000UL
+#define FIXADDR_TOP		0xfff00000UL
 #define FIXADDR_SIZE		(FIXADDR_TOP - FIXADDR_START)
 
 #define FIX_KMAP_NR_PTES	(FIXADDR_SIZE >> PAGE_SHIFT)
diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
index 45aeaac..ac2938f 100644
--- a/arch/arm/mm/highmem.c
+++ b/arch/arm/mm/highmem.c
@@ -18,19 +18,20 @@
 #include <asm/tlbflush.h>
 #include "mm.h"
 
-pte_t *fixmap_page_table;
-
 static inline void set_fixmap_pte(int idx, pte_t pte)
 {
 	unsigned long vaddr = __fix_to_virt(idx);
-	set_pte_ext(fixmap_page_table + idx, pte, 0);
+	pte_t *ptep = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
+
+	set_pte_ext(ptep, pte, 0);
 	local_flush_tlb_kernel_page(vaddr);
 }
 
 static inline pte_t get_fixmap_pte(unsigned long vaddr)
 {
-	unsigned long idx = __virt_to_fix(vaddr);
-	return *(fixmap_page_table + idx);
+	pte_t *ptep = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
+
+	return *ptep;
 }
 
 void *kmap(struct page *page)
@@ -84,7 +85,7 @@ void *kmap_atomic(struct page *page)
 	 * With debugging enabled, kunmap_atomic forces that entry to 0.
 	 * Make sure it was indeed properly unmapped.
 	 */
-	BUG_ON(!pte_none(*(fixmap_page_table + idx)));
+	BUG_ON(!pte_none(*get_fixmap_pte(vaddr)));
 #endif
 	/*
 	 * When debugging is off, kunmap_atomic leaves the previous mapping
@@ -134,7 +135,7 @@ void *kmap_atomic_pfn(unsigned long pfn)
 	idx = type + KM_TYPE_NR * smp_processor_id();
 	vaddr = __fix_to_virt(idx);
 #ifdef CONFIG_DEBUG_HIGHMEM
-	BUG_ON(!pte_none(*(fixmap_page_table + idx)));
+	BUG_ON(!pte_none(*get_fixmap_pte(vaddr)));
 #endif
 	set_fixmap_pte(idx, pfn_pte(pfn, kmap_prot));
 
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 8348ed6..5e5d0ba 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1327,7 +1327,7 @@ static void __init kmap_init(void)
 	pkmap_page_table = early_pte_alloc(pmd_off_k(PKMAP_BASE),
 		PKMAP_BASE, _PAGE_KERNEL_TABLE);
 
-	fixmap_page_table = early_pte_alloc(pmd_off_k(FIXADDR_START),
+	early_pte_alloc(pmd_off_k(FIXADDR_START),
 		FIXADDR_START, _PAGE_KERNEL_TABLE);
 #endif
 }
-- 
1.9.1