Arm boards currently use the default implementation of __udelay which consists of a spin-loop. AArch64 however provides an architectural timer with an event stream which can be enabled and waited upon with a few lines of assembly. This is more efficient and also avoids an issue on Arm FVPs where polling the counter frequently takes much longer than real-time.
Therefore, overrride __udelay for all armv8 boards to use the event stream. Macros for the relevant instructions already existed for mach-exynos, so pull these up to a common header file. I have tested this patch chain on qemu-system-aarch64 (virt,secure=on), FVP_Base_RevC and a Raspberry Pi 4. Peter Hoyes (2): arm: Move sev() and wfe() definitions to common Arm header file armv8: generic_timer: Use event stream for udelay arch/arm/cpu/armv8/Kconfig | 8 +++++++ arch/arm/cpu/armv8/generic_timer.c | 27 ++++++++++++++++++++++ arch/arm/include/asm/system.h | 15 ++++++++++-- arch/arm/mach-exynos/include/mach/system.h | 19 --------------- 4 files changed, 48 insertions(+), 21 deletions(-) -- 2.34.1
