diff options
Diffstat (limited to 'arch/arm/cpu')
| -rw-r--r-- | arch/arm/cpu/armv8/Kconfig | 8 | ||||
| -rw-r--r-- | arch/arm/cpu/armv8/generic_timer.c | 27 |
2 files changed, 35 insertions, 0 deletions
diff --git a/arch/arm/cpu/armv8/Kconfig b/arch/arm/cpu/armv8/Kconfig index 9f0fb369f77..199335cd604 100644 --- a/arch/arm/cpu/armv8/Kconfig +++ b/arch/arm/cpu/armv8/Kconfig @@ -191,6 +191,14 @@ config ARMV8_EA_EL3_FIRST Exception handling at all exception levels for External Abort and SError interrupt exception are taken in EL3. +config ARMV8_UDELAY_EVENT_STREAM + bool "Use the event stream for udelay" + default y if ARCH_VEXPRESS64 + help + Use the event stream provided by the AArch64 architectural timer for + delays. This is more efficient than the default polling + implementation. + menuconfig ARMV8_CRYPTO bool "ARM64 Accelerated Cryptographic Algorithms" diff --git a/arch/arm/cpu/armv8/generic_timer.c b/arch/arm/cpu/armv8/generic_timer.c index e4aa5a47455..1de7ec596fc 100644 --- a/arch/arm/cpu/armv8/generic_timer.c +++ b/arch/arm/cpu/armv8/generic_timer.c @@ -114,3 +114,30 @@ ulong timer_get_boot_us(void) return val / get_tbclk(); } + +#if CONFIG_IS_ENABLED(ARMV8_UDELAY_EVENT_STREAM) +void __udelay(unsigned long usec) +{ + u64 target = get_ticks() + usec_to_tick(usec); + + /* At EL2 or above, use the event stream to avoid polling CNTPCT_EL0 so often */ + if (current_el() >= 2) { + u32 cnthctl_val; + const u8 event_period = 0x7; + + asm volatile("mrs %0, cnthctl_el2" : "=r" (cnthctl_val)); + asm volatile("msr cnthctl_el2, %0" : : "r" + (cnthctl_val | CNTHCTL_EL2_EVNT_EN | CNTHCTL_EL2_EVNT_I(event_period))); + + while (get_ticks() + (1ULL << event_period) <= target) + wfe(); + + /* Reset the event stream */ + asm volatile("msr cnthctl_el2, %0" : : "r" (cnthctl_val)); + } + + /* Fall back to polling CNTPCT_EL0 */ + while (get_ticks() <= target) + ; +} +#endif |