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libgloss: riscv: Add support of clock() for semihosting
It's necessary to implement _times() in libsemihosting to add support of clock() function. SYS_ELAPSED and SYS_TICKFREQ semihosting calls are used to get a number of ticks which could be compatible with clock() interface and CLOCKS_PER_SEC value. clock() function from libc must return value which gives us seconds when it's divided by CLOCKS_PER_SEC. By default, CLOCKS_PER_SEC is 10**6 for RISC-V. However, semihosting's tick frequency may differ and usually it's 10**9. Thus, we have to obtain a real value of the tick frequency for the current semihosting setup and calculate a multiplier and use it for adjusting semihosting's number of ticks. E.g., if semihosting's ticks frequency is 10**9 then multiplier is 10**9 / 10**6 = 1000. Signed-off-by: Yuriy Kolerov <kolerov93@gmail.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,73 @@ | ||
| #include <stdint.h> | ||
| #include <stdbool.h> | ||
| #include <time.h> | ||
| #include <sys/types.h> | ||
| #include <sys/times.h> | ||
| #include <machine/syscall.h> | ||
| #include "semihost_syscall.h" | ||
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||
| clock_t | ||
| _times(struct tms *buf) | ||
| { | ||
| static bool initialized = false; | ||
| static clock_t semihosting_tick_freq = 0; | ||
| static bool semihosting_tick_freq_bigger = false; | ||
| static clock_t semihosting_tick_freq_multiplier = 0; | ||
| clock_t elapsed; | ||
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| /* SYS_ELAPSED semihosting call returns a single 64-bit value for 64-bit | ||
| targets and two 32-bit values for 32-bit targets. */ | ||
| #if __riscv_xlen == 32 | ||
| uint32_t data_block[2]; | ||
| #else | ||
| uint64_t data_block[1]; | ||
| #endif | ||
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|
||
| if (!initialized) | ||
| { | ||
| /* clock() function from libc must return value which gives us seconds | ||
| when it's divided by CLOCKS_PER_SEC. By default, CLOCKS_PER_SEC | ||
| is 10**6 for RISC-V. However, semihosting's tick frequency may | ||
| differ and usually it's 10**9. Thus, we have to obtain a real value | ||
| of the tick frequency for the current semihosting setup and | ||
| calculate a multiplier and use it for adjusting semihosting's | ||
| number of ticks. E.g., if semihosting's ticks frequency is 10**9 then | ||
| the multiplier is 10**9 / 10**6 = 1000. */ | ||
| semihosting_tick_freq = syscall_errno (SEMIHOST_tickfreq, NULL); | ||
|
|
||
| if (semihosting_tick_freq > CLOCKS_PER_SEC) | ||
| { | ||
| semihosting_tick_freq_multiplier = semihosting_tick_freq / CLOCKS_PER_SEC; | ||
| semihosting_tick_freq_bigger = true; | ||
| } | ||
| else | ||
| semihosting_tick_freq_multiplier = CLOCKS_PER_SEC / semihosting_tick_freq; | ||
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| initialized = true; | ||
| } | ||
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| /* SYS_ELAPSED semihosting call returns a number of ticks. */ | ||
| syscall_errno (SEMIHOST_elapsed, data_block); | ||
|
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||
| #if __riscv_xlen == 32 | ||
| elapsed = (((uint64_t) data_block[1]) << 32) | ((uint32_t) data_block[0]); | ||
| #else | ||
| elapsed = data_block[0]; | ||
| #endif | ||
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| /* Adjust the number of ticks to make it compatible with CLOCKS_PER_SEC. */ | ||
| if (semihosting_tick_freq_bigger) | ||
| elapsed /= semihosting_tick_freq_multiplier; | ||
| else | ||
| elapsed *= semihosting_tick_freq_multiplier; | ||
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||
| if (buf) | ||
| { | ||
| buf->tms_utime = elapsed; | ||
| buf->tms_stime = 0; | ||
| buf->tms_cutime = 0; | ||
| buf->tms_cstime = 0; | ||
| } | ||
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||
| return elapsed; | ||
| } |