arch/ppc64: Add <arch/mmio.h> stubs

The work may be incomplete, we only have an emulation
power8 at the moment in the tree.

Change-Id: Icdaa0995c8610dcc636923cc79b8455dfaeaa057
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/31996
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Timothy Pearson <tpearson@raptorengineering.com>

src/arch/ppc64/include/arch/mmio.h

@@ -0,0 +1,53 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * 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.
+ */
+
+#ifndef __ARCH_MMIO_H__
+#define __ARCH_MMIO_H__
+
+#include <stdint.h>
+
+/* NOTE: These are just stubs; if the architecture requires special
+ * care to avoid posted writes or cachelines, it is not yet done here.
+ */
+
+static inline uint8_t read8(const volatile void *addr)
+{
+	return *(volatile uint8_t *)addr;
+}
+
+static inline uint16_t read16(const volatile void *addr)
+{
+	return *(volatile uint16_t *)addr;
+}
+
+static inline uint32_t read32(const volatile void *addr)
+{
+	return *(volatile uint32_t *)addr;
+}
+
+static inline void write8(volatile void *addr, uint8_t val)
+{
+	*(volatile uint8_t *)addr = val;
+}
+
+static inline void write16(volatile void *addr, uint16_t val)
+{
+	*(volatile uint16_t *)addr = val;
+}
+
+static inline void write32(volatile void *addr, uint32_t val)
+{
+	*(volatile uint32_t *)addr = val;
+}
+
+#endif /* __ARCH_MMIO_H__ */