Merge pull request #783 from eclipse-threadx/devv6.5.2.202603_rel

Merged changes ahead of the v6.5.2.202603 release

1 files changed, 59 insertions, 10 deletions

diff --git a/ports/risc-v32/gnu/example_build/qemu_virt/hwtimer.c b/ports/risc-v32/gnu/example_build/qemu_virt/hwtimer.c
index 33c49b63..8d2f4e15 100644
--- a/ports/risc-v32/gnu/example_build/qemu_virt/hwtimer.c
+++ b/ports/risc-v32/gnu/example_build/qemu_virt/hwtimer.c
@@ -8,7 +8,7 @@
  * SPDX-License-Identifier: MIT
  **************************************************************************/
 
-#include "tx_port.h"
+#include "tx_api.h"
 #include "csr.h"
 #include "hwtimer.h"
 
@@ -16,20 +16,69 @@
 #define CLINT_TIME             (CLINT+0xBFF8)
 #define CLINT_TIMECMP(hart_id) (CLINT+0x4000+8*(hart_id))
 
+/* RV32 has no 64-bit load/store, so the 64-bit CLINT registers are
+   accessed as two volatile 32-bit MMIO words.  */
+#define MTIME_LO            (*(volatile uint32_t *)(CLINT_TIME))
+#define MTIME_HI            (*(volatile uint32_t *)(CLINT_TIME + 4))
+#define MTIMECMP_LO(hart)   (*(volatile uint32_t *)(CLINT_TIMECMP(hart)))
+#define MTIMECMP_HI(hart)   (*(volatile uint32_t *)(CLINT_TIMECMP(hart) + 4))
+
+/* RV32 mtime re-read the high word until it is stable, so a
+   low-word rollover between the two loads cannot tear the value.  */
+static uint64_t clint_time_read(void)
+{
+    uint32_t hi;
+    uint32_t lo;
+
+    do
+    {
+        hi = MTIME_HI;
+        lo = MTIME_LO;
+    } while (hi != MTIME_HI);
+
+    return ((uint64_t)hi << 32) | lo;
+}
+
+/* Only this hart writes its own mtimecmp, so a plain two-word read
+   cannot tear.  */
+static uint64_t clint_timecmp_read(int hart)
+{
+    uint32_t lo = MTIMECMP_LO(hart);
+    uint32_t hi = MTIMECMP_HI(hart);
+
+    return ((uint64_t)hi << 32) | lo;
+}
+
+/* RV32 mtimecmp write, safe sequence: park the low word at all-ones
+   first, so no intermediate 64-bit value compares below mtime and
+   raises a spurious timer interrupt.  */
+static void clint_timecmp_write(int hart, uint64_t value)
+{
+    MTIMECMP_LO(hart) = 0xFFFFFFFF;
+    MTIMECMP_HI(hart) = (uint32_t)(value >> 32);
+    MTIMECMP_LO(hart) = (uint32_t)value;
+}
 
 int hwtimer_init(void)
 {
-	int hart = riscv_get_core();
-	uint64_t time = *((uint64_t*)CLINT_TIME);
-    	*((uint64_t*)CLINT_TIMECMP(hart)) = time + TICKNUM_PER_TIMER;
-	return 0;
+    int hart = riscv_get_core();
+
+    clint_timecmp_write(hart, clint_time_read() + TICKNUM_PER_TIMER);
+    return 0;
 }
 
 int hwtimer_handler(void)
 {
-	int hart = riscv_get_core();
-        uint64_t time = *((uint64_t*)CLINT_TIME);
-        *((uint64_t*)CLINT_TIMECMP(hart)) = time + TICKNUM_PER_TIMER;
-	return 0;
-}
+    int hart = riscv_get_core();
+
+    /* Advance from the previous compare value, so trap
+       latency does not accumulate as tick drift  */
+    uint64_t next = clint_timecmp_read(hart) + TICKNUM_PER_TIMER;
+    uint64_t now = clint_time_read();
 
+    if (next <= now)
+        next = now + TICKNUM_PER_TIMER;
+
+    clint_timecmp_write(hart, next);
+    return 0;
+}