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

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 <[email protected]>
Reviewed-by: Daniel Kiper <[email protected]>

Author: xypron

grub-core/kern/riscv/efi/init.c

@@ -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