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authorKevin Cernekee <cernekee@gmail.com>2015-04-09 23:05:14 +0300
committerRob Herring <robh@kernel.org>2015-04-15 03:35:44 +0300
commit37786c7fee40771d13901de129af7e084ed48b55 (patch)
tree2c0dd93357852188da26585ea6e60c06f99265a8 /drivers/of
parentc954b36e3f5bfdd5aeceba49614a4864d7efec87 (diff)
downloadlinux-37786c7fee40771d13901de129af7e084ed48b55.tar.xz
of: Add helper function to check MMIO register endianness
SoC peripherals can come in several different flavors: - little-endian: registers always need to be accessed in LE mode (so the kernel should perform a swap if the CPU is running BE) - big-endian: registers always need to be accessed in BE mode (so the kernel should perform a swap if the CPU is running LE) - native-endian: the bus will automatically swap accesses, so the kernel should never swap Introduce a function that checks an OF device node to see whether it contains a "big-endian" or "native-endian" property. For the former case, always return true. For the latter case, return true iff the kernel was built for BE (implying that the BE MMIO accessors do not perform a swap). Otherwise return false, assuming LE registers. LE registers are assumed by default because most existing drivers (libahci, serial8250, usb) always use readl/writel in the absence of instructions to the contrary, so that will be our fallback. Signed-off-by: Kevin Cernekee <cernekee@gmail.com> Reviewed-by: Peter Hurley <peter@hurleysoftware.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Rob Herring <robh@kernel.org>
Diffstat (limited to 'drivers/of')
-rw-r--r--drivers/of/base.c23
1 files changed, 23 insertions, 0 deletions
diff --git a/drivers/of/base.c b/drivers/of/base.c
index 69566b6a876d..31ca3c8dae61 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -568,6 +568,29 @@ bool of_device_is_available(const struct device_node *device)
EXPORT_SYMBOL(of_device_is_available);
/**
+ * of_device_is_big_endian - check if a device has BE registers
+ *
+ * @device: Node to check for endianness
+ *
+ * Returns true if the device has a "big-endian" property, or if the kernel
+ * was compiled for BE *and* the device has a "native-endian" property.
+ * Returns false otherwise.
+ *
+ * Callers would nominally use ioread32be/iowrite32be if
+ * of_device_is_big_endian() == true, or readl/writel otherwise.
+ */
+bool of_device_is_big_endian(const struct device_node *device)
+{
+ if (of_property_read_bool(device, "big-endian"))
+ return true;
+ if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN) &&
+ of_property_read_bool(device, "native-endian"))
+ return true;
+ return false;
+}
+EXPORT_SYMBOL(of_device_is_big_endian);
+
+/**
* of_get_parent - Get a node's parent if any
* @node: Node to get parent
*