1 //===-- GPU implementation of the nanosleep function ----------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "src/time/nanosleep.h" 10 11 #include "src/__support/common.h" 12 #include "src/__support/macros/config.h" 13 #include "src/__support/time/gpu/time_utils.h" 14 15 namespace LIBC_NAMESPACE_DECL { 16 17 LLVM_LIBC_FUNCTION(int, nanosleep, 18 (const struct timespec *req, struct timespec *rem)) { 19 if (!GPU_CLOCKS_PER_SEC || !req) 20 return -1; 21 22 uint64_t nsecs = req->tv_nsec + req->tv_sec * TICKS_PER_SEC; 23 uint64_t tick_rate = TICKS_PER_SEC / GPU_CLOCKS_PER_SEC; 24 25 uint64_t start = gpu::fixed_frequency_clock(); 26 #if defined(LIBC_TARGET_ARCH_IS_NVPTX) 27 uint64_t end = start + (nsecs + tick_rate - 1) / tick_rate; 28 uint64_t cur = gpu::fixed_frequency_clock(); 29 // The NVPTX architecture supports sleeping and guaruntees the actual time 30 // slept will be somewhere between zero and twice the requested amount. Here 31 // we will sleep again if we undershot the time. 32 while (cur < end) { 33 if (__nvvm_reflect("__CUDA_ARCH") >= 700) 34 LIBC_INLINE_ASM("nanosleep.u32 %0;" ::"r"(nsecs)); 35 cur = gpu::fixed_frequency_clock(); 36 nsecs -= nsecs > cur - start ? cur - start : 0; 37 } 38 #elif defined(LIBC_TARGET_ARCH_IS_AMDGPU) 39 uint64_t end = start + (nsecs + tick_rate - 1) / tick_rate; 40 uint64_t cur = gpu::fixed_frequency_clock(); 41 // The AMDGPU architecture does not provide a sleep implementation with a 42 // known delay so we simply repeatedly sleep with a large value of ~960 clock 43 // cycles and check until we've passed the time using the known frequency. 44 __builtin_amdgcn_s_sleep(2); 45 while (cur < end) { 46 __builtin_amdgcn_s_sleep(15); 47 cur = gpu::fixed_frequency_clock(); 48 } 49 #else 50 // Sleeping is not supported. 51 if (rem) { 52 rem->tv_sec = req->tv_sec; 53 rem->tv_nsec = req->tv_nsec; 54 } 55 return -1; 56 #endif 57 uint64_t stop = gpu::fixed_frequency_clock(); 58 59 // Check to make sure we slept for at least the desired duration and set the 60 // remaining time if not. 61 uint64_t elapsed = (stop - start) * tick_rate; 62 if (elapsed < nsecs) { 63 if (rem) { 64 rem->tv_sec = (nsecs - elapsed) / TICKS_PER_SEC; 65 rem->tv_nsec = (nsecs - elapsed) % TICKS_PER_SEC; 66 } 67 return -1; 68 } 69 70 return 0; 71 } 72 73 } // namespace LIBC_NAMESPACE_DECL 74