1 files changed, 73 insertions, 0 deletions

diff --git a/arch/arm/mm/minicache.c b/arch/arm/mm/minicache.c
new file mode 100644
index 000000000000..dedf2ab01b2a
--- /dev/null
+++ b/arch/arm/mm/minicache.c
@@ -0,0 +1,73 @@
+/*
+ *  linux/arch/arm/mm/minicache.c
+ *
+ *  Copyright (C) 2001 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This handles the mini data cache, as found on SA11x0 and XScale
+ * processors.  When we copy a user page page, we map it in such a way
+ * that accesses to this page will not touch the main data cache, but
+ * will be cached in the mini data cache.  This prevents us thrashing
+ * the main data cache on page faults.
+ */
+#include <linux/init.h>
+#include <linux/mm.h>
+
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
+
+/*
+ * 0xffff8000 to 0xffffffff is reserved for any ARM architecture
+ * specific hacks for copying pages efficiently.
+ */
+#define minicache_address (0xffff8000)
+#define minicache_pgprot __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | \
+                                  L_PTE_CACHEABLE)
+
+static pte_t *minicache_pte;
+
+/*
+ * Note that this is intended to be called only from the copy_user_page
+ * asm code; anything else will require special locking to prevent the
+ * mini-cache space being re-used.  (Note: probably preempt unsafe).
+ *
+ * We rely on the fact that the minicache is 2K, and we'll be pushing
+ * 4K of data through it, so we don't actually have to specifically
+ * flush the minicache when we change the mapping.
+ *
+ * Note also: assert(PAGE_OFFSET <= virt < high_memory).
+ * Unsafe: preempt, kmap.
+ */
+unsigned long map_page_minicache(unsigned long virt)
+{
+        set_pte(minicache_pte, pfn_pte(__pa(virt) >> PAGE_SHIFT, minicache_pgprot));
+        flush_tlb_kernel_page(minicache_address);
+
+        return minicache_address;
+}
+
+static int __init minicache_init(void)
+{
+        pgd_t *pgd;
+        pmd_t *pmd;
+
+        spin_lock(&init_mm.page_table_lock);
+
+        pgd = pgd_offset_k(minicache_address);
+        pmd = pmd_alloc(&init_mm, pgd, minicache_address);
+        if (!pmd)
+                BUG();
+        minicache_pte = pte_alloc_kernel(&init_mm, pmd, minicache_address);
+        if (!minicache_pte)
+                BUG();
+
+        spin_unlock(&init_mm.page_table_lock);
+
+        return 0;
+}
+
+core_initcall(minicache_init);