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author | Kevin Cernekee <cernekee@gmail.com> | 2015-04-09 13:05:14 -0700 |
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committer | Rob Herring <robh@kernel.org> | 2015-04-14 19:35:44 -0500 |
commit | 37786c7fee40771d13901de129af7e084ed48b55 (patch) | |
tree | 2c0dd93357852188da26585ea6e60c06f99265a8 | |
parent | c954b36e3f5bfdd5aeceba49614a4864d7efec87 (diff) | |
download | op-kernel-dev-37786c7fee40771d13901de129af7e084ed48b55.zip op-kernel-dev-37786c7fee40771d13901de129af7e084ed48b55.tar.gz |
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>
-rw-r--r-- | drivers/of/base.c | 23 | ||||
-rw-r--r-- | include/linux/of.h | 6 |
2 files changed, 29 insertions, 0 deletions
diff --git a/drivers/of/base.c b/drivers/of/base.c index 69566b6..31ca3c8 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 * diff --git a/include/linux/of.h b/include/linux/of.h index dfde07e..a0cd62e 100644 --- a/include/linux/of.h +++ b/include/linux/of.h @@ -305,6 +305,7 @@ extern int of_property_read_string_helper(struct device_node *np, extern int of_device_is_compatible(const struct device_node *device, const char *); extern bool of_device_is_available(const struct device_node *device); +extern bool of_device_is_big_endian(const struct device_node *device); extern const void *of_get_property(const struct device_node *node, const char *name, int *lenp); @@ -466,6 +467,11 @@ static inline bool of_device_is_available(const struct device_node *device) return false; } +static inline bool of_device_is_big_endian(const struct device_node *device) +{ + return false; +} + static inline struct property *of_find_property(const struct device_node *np, const char *name, int *lenp) |