[PATCH 1/1] riscv: use time register in grub_efi_get_time_ms()

* [PATCH 1/1] riscv: use time register in grub_efi_get_time_ms()
@ 2024-08-12 14:13 Heinrich Schuchardt
  2024-08-13 13:52 ` Daniel Kiper via Grub-devel
  0 siblings, 1 reply; 4+ messages in thread
From: Heinrich Schuchardt @ 2024-08-12 14:13 UTC (permalink / raw)
  To: Daniel Kiper; +Cc: GRUB development, Heinrich Schuchardt

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>
---
 grub-core/kern/riscv/efi/init.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/grub-core/kern/riscv/efi/init.c b/grub-core/kern/riscv/efi/init.c
index 38795fe67..519e4625a 100644
--- a/grub-core/kern/riscv/efi/init.c
+++ b/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
 
-- 
2.45.2


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