[RFC 1/6] atmel: add atmel_io.h

[Ben Dooks]

The AVR32 and ARM (AT91) architectures share a number of drivers which
need to access the on chip peripherals. The current drivers work with
the default endian configuration, however it is possilbe to run some of
the ATMEL ARM architectures in big endian mode.

If we change the drivers from __raw to _relaxed IO accesors then the ARM
side works but the AVR32 will not. The _relaxed assume the bus is little
endian and the __raw are native. The AVR32 is native big endian so these
are not the right functions.

To sort this out, and avoid a number of drivers having #ifdef for the
AVR32 case we add <linux/atmel_io.h> to provide some AT91/AVR32 independant
IO accessor functions.

Signed-off-by: Ben Dooks <ben.dooks at codethink.co.uk>
--
CC: Haavard Skinnemoen <hskinnemoen at gmail.com>
CC: Hans-Christian Egtvedt <egtvedt at samfundet.no>
CC: Andrew Victor <linux at maxim.org.za>
CC: Nicolas Ferre <nicolas.ferre at atmel.com>
CC: linux-arm-kernel at lists.infradead.org
---
 include/linux/atmel_io.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 include/linux/atmel_io.h

diff --git a/include/linux/atmel_io.h b/include/linux/atmel_io.h
new file mode 100644
index 0000000..1234e88
--- /dev/null
+++ b/include/linux/atmel_io.h
@@ -0,0 +1,25 @@
+/* Atmel AT91/AVR32 independant IO
+ *
+ * Copyright 2015 Codethink Ltd.
+ * Ben Dooks <ben.dooks at codethink.co.uk>
+ *
+ * Provide architecture indendant, endian-safe IO accessor functions
+ */
+
+#ifdef CONFIG_AVR32
+/* For AVR32 the readl and writel relaxed will do an extra byte reverse
+ * as the peripherals are already in the same endian-ness as the CPU and
+ * readl/writel assume little endian where the CPU is big endian
+ */
+#define atmel_oc_readl	__raw_readl
+#define atmel_oc_writel	__raw_writel
+
+#define atmel_oc_readw	__raw_readw
+#define atmel_oc_writew	__raw_writew
+#else
+#define atmel_oc_readl	readl_relaxed
+#define atmel_oc_writel	writel_relaxed
+
+#define atmel_oc_readw	readw_relaxed
+#define atmel_oc_writew	writew_relaxed
+#endif
-- 
2.1.4