ACPI: Introduce acpi_os_ioremap()

Commit ca9b600be38c ("ACPI / PM: Make suspend_nvs_save() use
acpi_os_map_memory()") attempted to prevent the code in osl.c and nvs.c
from using different ioremap() variants by making the latter use
acpi_os_map_memory() for mapping the NVS pages.  However, that also
requires acpi_os_unmap_memory() to be used for unmapping them, which
causes synchronize_rcu() to be executed many times in a row
unnecessarily and introduces substantial delays during resume on some
systems.

Instead of using acpi_os_map_memory() for mapping the NVS pages in nvs.c
introduce acpi_os_ioremap() calling ioremap_cache() and make the code in
both osl.c and nvs.c use it.

Reported-by: Jeff Chua <jeff.chua.linux@gmail.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/acpi_io.h b/include/linux/acpi_io.h
new file mode 100644
index 000000000000..7180013a4a3a
--- /dev/null
+++ b/include/linux/acpi_io.h
@@ -0,0 +1,16 @@
+#ifndef _ACPI_IO_H_
+#define _ACPI_IO_H_
+
+#include <linux/io.h>
+#include <acpi/acpi.h>
+
+static inline void __iomem *acpi_os_ioremap(acpi_physical_address phys,
+					    acpi_size size)
+{
+       return ioremap_cache(phys, size);
+}
+
+int acpi_os_map_generic_address(struct acpi_generic_address *addr);
+void acpi_os_unmap_generic_address(struct acpi_generic_address *addr);
+
+#endif