From 05bc50b854935cea8d0fa54a3386f1ece8235293 Mon Sep 17 00:00:00 2001 From: Oleksij Rempel Date: Wed, 6 Sep 2017 16:44:07 +0200 Subject: of: base: port of_device_is_big_endian from linux |commit 37786c7fee40771d13901de129af7e084ed48b55 |Author: Kevin Cernekee |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 Signed-off-by: Sascha Hauer --- drivers/of/base.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'drivers/of') diff --git a/drivers/of/base.c b/drivers/of/base.c index ea330d1310..95bea4ee83 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c @@ -1621,6 +1621,29 @@ 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 -- cgit v1.2.3