MN10300: Allow some cacheflushes to be avoided if cache snooping is available

The AM34 core is able to do cache snooping, and so can skip some of the cache
flushing.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 119 insertions, 0 deletions

diff --git a/arch/mn10300/mm/cache-inv-icache.c b/arch/mn10300/mm/cache-inv-icache.c
new file mode 100644
index 00000000000..4a3f7afcfe5
--- /dev/null
+++ b/arch/mn10300/mm/cache-inv-icache.c
@@ -0,0 +1,119 @@
+/* Invalidate icache when dcache doesn't need invalidation as it's in
+ * write-through mode
+ *
+ * Copyright (C) 2010 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <asm/cacheflush.h>
+
+/**
+ * flush_icache_page_range - Flush dcache and invalidate icache for part of a
+ *				single page
+ * @start: The starting virtual address of the page part.
+ * @end: The ending virtual address of the page part.
+ *
+ * Invalidate the icache for part of a single page, as determined by the
+ * virtual addresses given.  The page must be in the paged area.  The dcache is
+ * not flushed as the cache must be in write-through mode to get here.
+ */
+static void flush_icache_page_range(unsigned long start, unsigned long end)
+{
+	unsigned long addr, size, off;
+	struct page *page;
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *ppte, pte;
+
+	/* work out how much of the page to flush */
+	off = start & ~PAGE_MASK;
+	size = end - start;
+
+	/* get the physical address the page is mapped to from the page
+	 * tables */
+	pgd = pgd_offset(current->mm, start);
+	if (!pgd || !pgd_val(*pgd))
+		return;
+
+	pud = pud_offset(pgd, start);
+	if (!pud || !pud_val(*pud))
+		return;
+
+	pmd = pmd_offset(pud, start);
+	if (!pmd || !pmd_val(*pmd))
+		return;
+
+	ppte = pte_offset_map(pmd, start);
+	if (!ppte)
+		return;
+	pte = *ppte;
+	pte_unmap(ppte);
+
+	if (pte_none(pte))
+		return;
+
+	page = pte_page(pte);
+	if (!page)
+		return;
+
+	addr = page_to_phys(page);
+
+	/* invalidate the icache coverage on that region */
+	mn10300_icache_inv_range2(addr + off, size);
+}
+
+/**
+ * flush_icache_range - Globally flush dcache and invalidate icache for region
+ * @start: The starting virtual address of the region.
+ * @end: The ending virtual address of the region.
+ *
+ * This is used by the kernel to globally flush some code it has just written
+ * from the dcache back to RAM and then to globally invalidate the icache over
+ * that region so that that code can be run on all CPUs in the system.
+ */
+void flush_icache_range(unsigned long start, unsigned long end)
+{
+	unsigned long start_page, end_page;
+
+	if (end > 0x80000000UL) {
+		/* addresses above 0xa0000000 do not go through the cache */
+		if (end > 0xa0000000UL) {
+			end = 0xa0000000UL;
+			if (start >= end)
+				return;
+		}
+
+		/* kernel addresses between 0x80000000 and 0x9fffffff do not
+		 * require page tables, so we just map such addresses
+		 * directly */
+		start_page = (start >= 0x80000000UL) ? start : 0x80000000UL;
+		mn10300_dcache_flush_range(start_page, end);
+		mn10300_icache_inv_range(start_page, end);
+		if (start_page == start)
+			return;
+		end = start_page;
+	}
+
+	start_page = start & PAGE_MASK;
+	end_page = end & PAGE_MASK;
+
+	if (start_page == end_page) {
+		/* the first and last bytes are on the same page */
+		flush_icache_page_range(start, end);
+	} else if (start_page + 1 == end_page) {
+		/* split over two virtually contiguous pages */
+		flush_icache_page_range(start, end_page);
+		flush_icache_page_range(end_page, end);
+	} else {
+		/* more than 2 pages; just flush the entire cache */
+		mn10300_icache_inv();
+	}
+}
+EXPORT_SYMBOL(flush_icache_range);