resources: add io-mapping functions to dynamically map large device apertures

Impact: add new generic io_map_*() APIs

Graphics devices have large PCI apertures which would consume a significant
fraction of a 32-bit address space if mapped during driver initialization.
Using ioremap at runtime is impractical as it is too slow.

This new set of interfaces uses atomic mappings on 32-bit processors and a
large static mapping on 64-bit processors to provide reasonable 32-bit
performance and optimal 64-bit performance.

The current implementation sits atop the io_map_atomic fixmap-based
mechanism for 32-bit processors.

This includes some editorial suggestions from Randy Dunlap for
Documentation/io-mapping.txt

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 118 insertions, 0 deletions

diff --git a/include/linux/io-mapping.h b/include/linux/io-mapping.h
new file mode 100644
index 000000000000..1b566993db6e
--- /dev/null
+++ b/include/linux/io-mapping.h
@@ -0,0 +1,118 @@
+/*
+ * Copyright © 2008 Keith Packard <keithp@keithp.com>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#ifndef _LINUX_IO_MAPPING_H
+#define _LINUX_IO_MAPPING_H
+
+#include <linux/types.h>
+#include <asm/io.h>
+#include <asm/page.h>
+#include <asm/iomap.h>
+
+/*
+ * The io_mapping mechanism provides an abstraction for mapping
+ * individual pages from an io device to the CPU in an efficient fashion.
+ *
+ * See Documentation/io_mapping.txt
+ */
+
+/* this struct isn't actually defined anywhere */
+struct io_mapping;
+
+#ifdef CONFIG_X86_64
+
+/* Create the io_mapping object*/
+static inline struct io_mapping *
+io_mapping_create_wc(unsigned long base, unsigned long size)
+{
+        return (struct io_mapping *) ioremap_wc(base, size);
+}
+
+static inline void
+io_mapping_free(struct io_mapping *mapping)
+{
+        iounmap(mapping);
+}
+
+/* Atomic map/unmap */
+static inline void *
+io_mapping_map_atomic_wc(struct io_mapping *mapping, unsigned long offset)
+{
+        return ((char *) mapping) + offset;
+}
+
+static inline void
+io_mapping_unmap_atomic(void *vaddr)
+{
+}
+
+/* Non-atomic map/unmap */
+static inline void *
+io_mapping_map_wc(struct io_mapping *mapping, unsigned long offset)
+{
+        return ((char *) mapping) + offset;
+}
+
+static inline void
+io_mapping_unmap(void *vaddr)
+{
+}
+
+#endif /* CONFIG_X86_64 */
+
+#ifdef CONFIG_X86_32
+static inline struct io_mapping *
+io_mapping_create_wc(unsigned long base, unsigned long size)
+{
+        return (struct io_mapping *) base;
+}
+
+static inline void
+io_mapping_free(struct io_mapping *mapping)
+{
+}
+
+/* Atomic map/unmap */
+static inline void *
+io_mapping_map_atomic_wc(struct io_mapping *mapping, unsigned long offset)
+{
+        offset += (unsigned long) mapping;
+        return iomap_atomic_prot_pfn(offset >> PAGE_SHIFT, KM_USER0,
+                                     __pgprot(__PAGE_KERNEL_WC));
+}
+
+static inline void
+io_mapping_unmap_atomic(void *vaddr)
+{
+        iounmap_atomic(vaddr, KM_USER0);
+}
+
+static inline void *
+io_mapping_map_wc(struct io_mapping *mapping, unsigned long offset)
+{
+        offset += (unsigned long) mapping;
+        return ioremap_wc(offset, PAGE_SIZE);
+}
+
+static inline void
+io_mapping_unmap(void *vaddr)
+{
+        iounmap(vaddr);
+}
+#endif /* CONFIG_X86_32 */
+
+#endif /* _LINUX_IO_MAPPING_H */