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kern/riscv/efi/init: Use time register in grub_efi_get_time_ms()

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The cycle register is not guaranteed to count at constant frequency.
If it is counting at all depends on the state the performance monitoring
unit. Use the time register to measure time.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Heinrich Schuchardt 2024-08-12 16:13:18 +02:00 committed by Daniel Kiper
parent 9c34d56c2d
commit c5ae124e11
1 changed files with 7 additions and 8 deletions
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15
grub-core/kern/riscv/efi/init.c
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@ -33,16 +33,15 @@ grub_efi_get_time_ms (void)
grub_uint64_t tmr;
#if __riscv_xlen == 64
asm volatile ("rdcycle %0" : "=r" (tmr));
asm volatile ("rdtime %0" : "=r"(tmr));
#else
grub_uint32_t lo, hi, tmp;
asm volatile (
"1:\n"
"rdcycleh %0\n"
"rdcycle %1\n"
"rdcycleh %2\n"
"bne %0, %2, 1b"
: "=&r" (hi), "=&r" (lo), "=&r" (tmp));
asm volatile ("1:\n"
"rdtimeh %0\n"
"rdtime %1\n"
"rdtimeh %2\n"
"bne %0, %2, 1b"
: "=&r" (hi), "=&r" (lo), "=&r" (tmp));
tmr = ((grub_uint64_t)hi << 32) | lo;
#endif