From 37786c7fee40771d13901de129af7e084ed48b55 Mon Sep 17 00:00:00 2001 From: Kevin Cernekee Date: Thu, 9 Apr 2015 13:05:14 -0700 Subject: [PATCH] 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 Reviewed-by: Peter Hurley Acked-by: Greg Kroah-Hartman Signed-off-by: Rob Herring --- Reading git-format-patch failed