diff options
| -rw-r--r-- | arch/riscv/kernel/unaligned_access_speed.c | 59 |
1 files changed, 40 insertions, 19 deletions
diff --git a/arch/riscv/kernel/unaligned_access_speed.c b/arch/riscv/kernel/unaligned_access_speed.c index 576ca5c82db6..02c8391d4e35 100644 --- a/arch/riscv/kernel/unaligned_access_speed.c +++ b/arch/riscv/kernel/unaligned_access_speed.c @@ -63,58 +63,79 @@ measure_cycles(void (*func)(void *dst, const void *src, size_t len), return cycles; } -#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS -static int check_unaligned_access(void *param) +/* + * Return: + * 1 if unaligned accesses are fast + * 0 if unaligned accesses are slow + * -1 if check cannot be done + */ +static int __maybe_unused +compare_unaligned_access(void (*word_copy)(void *dst, const void *src, size_t len), + void (*byte_copy)(void *dst, const void *src, size_t len), + void *buf) { int cpu = smp_processor_id(); u64 word_cycles; u64 byte_cycles; + void *dst, *src; + bool fast; int ratio; - struct page *page = param; - void *dst; - void *src; - long speed = RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW; - - if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN) - return 0; /* Make an unaligned destination buffer. */ - dst = (void *)((unsigned long)page_address(page) | 0x1); + dst = (void *)((unsigned long)buf | 0x1); /* Unalign src as well, but differently (off by 1 + 2 = 3). */ src = dst + (MISALIGNED_BUFFER_SIZE / 2); src += 2; - word_cycles = measure_cycles(__riscv_copy_words_unaligned, dst, src, MISALIGNED_COPY_SIZE); - byte_cycles = measure_cycles(__riscv_copy_bytes_unaligned, dst, src, MISALIGNED_COPY_SIZE); + word_cycles = measure_cycles(word_copy, dst, src, MISALIGNED_COPY_SIZE); + byte_cycles = measure_cycles(byte_copy, dst, src, MISALIGNED_COPY_SIZE); /* Don't divide by zero. */ if (!word_cycles || !byte_cycles) { pr_warn("cpu%d: rdtime lacks granularity needed to measure unaligned access speed\n", cpu); - return 0; + return -1; } - if (word_cycles < byte_cycles) - speed = RISCV_HWPROBE_MISALIGNED_SCALAR_FAST; + fast = word_cycles < byte_cycles; ratio = div_u64((byte_cycles * 100), word_cycles); pr_info("cpu%d: Ratio of byte access time to unaligned word access is %d.%02d, unaligned accesses are %s\n", cpu, ratio / 100, ratio % 100, - (speed == RISCV_HWPROBE_MISALIGNED_SCALAR_FAST) ? "fast" : "slow"); + fast ? "fast" : "slow"); - per_cpu(misaligned_access_speed, cpu) = speed; + return fast; +} + +#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS +static int check_unaligned_access(struct page *page) +{ + void *buf = page_address(page); + int cpu = smp_processor_id(); + int ret; + + if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN) + return 0; + + ret = compare_unaligned_access(__riscv_copy_words_unaligned, + __riscv_copy_bytes_unaligned, buf); + if (ret < 0) + return 0; /* * Set the value of fast_misaligned_access of a CPU. These operations * are atomic to avoid race conditions. */ - if (speed == RISCV_HWPROBE_MISALIGNED_SCALAR_FAST) + if (ret) { + per_cpu(misaligned_access_speed, cpu) = RISCV_HWPROBE_MISALIGNED_SCALAR_FAST; cpumask_set_cpu(cpu, &fast_misaligned_access); - else + } else { + per_cpu(misaligned_access_speed, cpu) = RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW; cpumask_clear_cpu(cpu, &fast_misaligned_access); + } return 0; } |