Adapt mtimecmp read/write for per-hart registers

Previously, mtimecmp was accessed at a fixed MMIO address assuming a
single core. Each hart has its own mtimecmp register at distinct
offsets, so update mtimecmp read and write functions to index based on
the current hart ID, ensuring correct timer compare handling in SMP
systems.

Author: visitorckw

arch/riscv/hal.c

@@ -131,11 +131,14 @@ static inline uint64_t mtime_r(void)
 /* Safely read the 64-bit 'mtimecmp' register. */
 static inline uint64_t mtimecmp_r(void)
 {
-    uint32_t hi, lo;
+    uint32_t hi, lo, hartid;
+
+    hartid = read_csr(mhartid);
+
     do {
-        hi = MTIMECMP_H;
-        lo = MTIMECMP_L;
-    } while (hi != MTIMECMP_H);
+        hi = * (volatile uint32_t *) (CLINT_BASE + 0x4004u + 8 * hartid);
+        lo = * (volatile uint32_t *) (CLINT_BASE + 0x4000u + 8 * hartid);
+    } while (hi != *(volatile uint32_t *) (CLINT_BASE + 0x4004u + 8 * hartid));
     return CT64(hi, lo);
 }
 
@@ -152,10 +155,11 @@ static inline void mtimecmp_w(uint64_t val)
     /* Disable interrupts during the critical section to ensure atomicity */
     uint32_t old_mie = read_csr(mie);
     write_csr(mie, old_mie & ~MIE_MTIE);
+    uint32_t hartid = read_csr(mhartid);
 
-    MTIMECMP_L = 0xFFFFFFFF; /* Set to maximum to prevent spurious interrupt */
-    MTIMECMP_H = (uint32_t) (val >> 32); /* Set high word */
-    MTIMECMP_L = (uint32_t) val;         /* Set low word to final value */
+    * (volatile uint32_t *) (CLINT_BASE + 0x4000u + 8 * hartid) = 0xFFFFFFFF; /* Set to maximum to prevent spurious interrupt */
+    * (volatile uint32_t *) (CLINT_BASE + 0x4004u + 8 * hartid) = (uint32_t) (val >> 32); /* Set high word */
+    * (volatile uint32_t *) (CLINT_BASE + 0x4000u + 8 * hartid) = (uint32_t) val;         /* Set low word to final value */
 
     /* Re-enable timer interrupts if they were previously enabled */
     write_csr(mie, old_mie);