[U-Boot] [PATCH 1/3] Create API to map between CPU physical and bus addresses

[Stephen Warren]

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 at wwwdotorg.org>
---
These patches depend on previous DWC2 rework that's in the topic/dwc2
branch of the USB repo.

These patches conflict with patches Masahiro has posted to move
arch/arm/cpu/arm1176/bcm2835 to arch/arm/mach-bcm283x(?).

I expect I'll have to rebase this series after the upcoming release once
those two things are merged into u-boot.git. Still, reviews could begin
before that.
---
 drivers/Kconfig    |  8 ++++++++
 include/phys2bus.h | 25 +++++++++++++++++++++++++
 2 files changed, 33 insertions(+)
 create mode 100644 include/phys2bus.h

diff --git a/drivers/Kconfig b/drivers/Kconfig
index dcce532e2df2..941aa0c2612a 100644
--- 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
index 000000000000..87b6d69aa617
--- /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
-- 
1.9.1