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>

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>
Stephen Warren · Marek Vasut
1 parent fc909c0563
Showing 2 changed files with 33 additions and 0 deletions Side-by-side Diff
drivers/Kconfig
include/phys2bus.h
@@ -53,4 +53,12 @@
 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.
+/*
+ * 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
...	...	@@ -53,4 +53,12 @@
53	53	source "drivers/thermal/Kconfig"
54	54
55	55	endmenu
	56	+
	57	+config PHYS_TO_BUS
	58	+ bool
	59	+ help
	60	+ Some SoCs use a different address map for CPU physical addresses and
	61	+ peripheral DMA master accesses. If yours does, select this option in
	62	+ your platform's Kconfig, and implement the appropriate mapping
	63	+ functions in your platform's support code.
	1	+/*
	2	+ * Copyright 2015 Stephen Warren
	3	+ *
	4	+ * SPDX-License-Identifier: GPL-2.0+
	5	+ */
	6	+
	7	+#ifndef _BUS_ADDR_H
	8	+#define _BUS_ADDR_H
	9	+
	10	+#ifdef CONFIG_PHYS_TO_BUS
	11	+unsigned long phys_to_bus(unsigned long phys);
	12	+unsigned long bus_to_phys(unsigned long bus);
	13	+#else
	14	+static inline unsigned long phys_to_bus(unsigned long phys)
	15	+{
	16	+ return phys;
	17	+}
	18	+
	19	+static inline unsigned long bus_to_phys(unsigned long bus)
	20	+{
	21	+ return bus;
	22	+}
	23	+#endif
	24	+
	25	+#endif