Create API to map between CPU physical and bus addresses

On some SoCs, DMA-capable peripherals see a different address space to
the CPU's physical address space. Create an API to allow platform-agnostic
drivers to convert between the two address spaces when programming DMA
operations.

This API will exist on all platforms, but will have a dummy implementation
when this feature is not required. Other platforms will enable
CONFIG_PHYS_TO_BUS and provide the required implementation.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>

diff --git a/drivers/Kconfig b/drivers/Kconfig
index dcce532e2df200ed4f82a4c45f0e14982ee26d1a..941aa0c2612afee95afad1cbcacfc12fa640a4df 100644 (file)
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -53,3 +53,11 @@ source "drivers/crypto/Kconfig"
 source "drivers/thermal/Kconfig"
 
 endmenu
+
+config PHYS_TO_BUS
+       bool
+       help
+         Some SoCs use a different address map for CPU physical addresses and
+         peripheral DMA master accesses. If yours does, select this option in
+         your platform's Kconfig, and implement the appropriate mapping
+         functions in your platform's support code.

diff --git a/include/phys2bus.h b/include/phys2bus.h
new file mode 100644 (file)
index 0000000..87b6d69
--- /dev/null
+++ b/include/phys2bus.h
@@ -0,0 +1,25 @@
+/*
+ * Copyright 2015 Stephen Warren
+ *
+ * SPDX-License-Identifier:     GPL-2.0+
+ */
+
+#ifndef _BUS_ADDR_H
+#define _BUS_ADDR_H
+
+#ifdef CONFIG_PHYS_TO_BUS
+unsigned long phys_to_bus(unsigned long phys);
+unsigned long bus_to_phys(unsigned long bus);
+#else
+static inline unsigned long phys_to_bus(unsigned long phys)
+{
+       return phys;
+}
+
+static inline unsigned long bus_to_phys(unsigned long bus)
+{
+       return bus;
+}
+#endif
+
+#endif