diff options
Diffstat (limited to 'payloads/libpayload/arch/x86')
| -rw-r--r-- | payloads/libpayload/arch/x86/Makefile.inc | 1 | ||||
| -rw-r--r-- | payloads/libpayload/arch/x86/delay.c | 52 |
2 files changed, 53 insertions, 0 deletions
diff --git a/payloads/libpayload/arch/x86/Makefile.inc b/payloads/libpayload/arch/x86/Makefile.inc index 268df1e542..0cc477399a 100644 --- a/payloads/libpayload/arch/x86/Makefile.inc +++ b/payloads/libpayload/arch/x86/Makefile.inc @@ -35,6 +35,7 @@ libc-y += timer.c coreboot.c util.S libc-y += exec.S virtual.c libc-y += selfboot.c libc-y += exception_asm.S exception.c +libc-y += delay.c # Will fall back to default_memXXX() in libc/memory.c if GPL not allowed. libc-$(CONFIG_LP_GPL) += string.c diff --git a/payloads/libpayload/arch/x86/delay.c b/payloads/libpayload/arch/x86/delay.c new file mode 100644 index 0000000000..541cf7a436 --- /dev/null +++ b/payloads/libpayload/arch/x86/delay.c @@ -0,0 +1,52 @@ +/* + * This file is part of the libpayload project. + * + * Copyright (C) 2018 Google LLC. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. The name of the author may not be used to endorse or promote products + * derived from this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include <libpayload.h> + +/* The pause instruction can delay 10-140 CPU cycles, so avoid calling it when + * getting close to finishing. Depending on the timer source, the timer can be + * running at CPU frequency, bus frequency, or some arbitrary value. We assume + * that the timer is running at the CPU frequency. */ +#define PAUSE_THRESHOLD_TICKS 150 + +void arch_ndelay(uint64_t ns) +{ + uint64_t delta = ns * timer_hz() / NSECS_PER_SEC; + uint64_t pause_delta = 0; + uint64_t start = timer_raw_value(); + + if (delta > PAUSE_THRESHOLD_TICKS) + pause_delta = delta - PAUSE_THRESHOLD_TICKS; + + while (timer_raw_value() - start < pause_delta) + asm volatile("pause\n\t"); + + while (timer_raw_value() - start < delta) + continue; +} |