|commit 37786c7fee40771d13901de129af7e084ed48b55
|Author: Kevin Cernekee <cernekee@xxxxxxxxx>
|Date: Thu Apr 9 13:05:14 2015 -0700
|
| 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: Oleksij Rempel <linux@xxxxxxxxxxxxxxxx>
---
drivers/of/base.c | 23 +++++++++++++++++++++++
include/of.h | 6 ++++++
2 files changed, 29 insertions(+)
diff --git a/drivers/of/base.c b/drivers/of/base.c
index ea330d131..95bea4ee8 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1622,6 +1622,29 @@ int 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/of.h b/include/of.h
index 0ba73f197..9ba771a39 100644
--- a/include/of.h
+++ b/include/of.h
@@ -150,6 +150,7 @@ extern int of_machine_is_compatible(const char *compat);
extern int of_device_is_compatible(const struct device_node *device,
const char *compat);
extern int of_device_is_available(const struct device_node *device);
+extern bool of_device_is_big_endian(const struct device_node *device);
extern struct device_node *of_get_parent(const struct device_node *node);
extern struct device_node *of_get_next_available_child(
@@ -595,6 +596,11 @@ static inline int of_device_is_available(const struct device_node *device)
return 0;
}
+static inline bool of_device_is_big_endian(const struct device_node *device)
+{
+ return false;
+}
+
static inline void of_alias_scan(void)
{
}
--
2.11.0
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