Merge branch 'bugfix/esp32p4_remove_fence' into 'master'

fix(riscv): Remove the memory barrier when changing interrupt threshold

Closes IDF-7898

See merge request espressif/esp-idf!29119

components/riscv/include/riscv/rv_utils.h

@@ -60,15 +60,6 @@ FORCE_INLINE_ATTR void __attribute__((always_inline)) rv_utils_wait_for_intr(voi
     asm volatile ("wfi\n");
 }
 
-/* ------------------------------------------------- Memory Barrier ----------------------------------------------------
- *
- * ------------------------------------------------------------------------------------------------------------------ */
-//TODO: IDF-7898
-FORCE_INLINE_ATTR void rv_utils_memory_barrier(void)
-{
-    asm volatile("fence iorw, iorw" : : : "memory");
-}
-
 /* -------------------------------------------------- CPU Registers ----------------------------------------------------
  *
  * ------------------------------------------------------------------------------------------------------------------ */
@@ -191,15 +182,11 @@ FORCE_INLINE_ATTR uint32_t __attribute__((always_inline)) rv_utils_set_intlevel(
 
     REG_SET_FIELD(CLIC_INT_THRESH_REG, CLIC_CPU_INT_THRESH, ((intlevel << (8 - NLBITS))) | 0x1f);
     /**
-     * TODO: IDF-7898
+     * After writing the threshold register, the new threshold is not directly taken into account by the CPU.
-     * Here is an issue that,
+     * By executing ~8 nop instructions, or by performing a memory load right now, the previous memory write
-     * 1. Set the CLIC_INT_THRESH_REG to mask off interrupts whose level is lower than `intlevel`.
+     * operations is forced, making the new threshold active. It is then safe to re-enable MIE bit in mstatus.
-     * 2. Set MSTATUS_MIE (global interrupt), then program may jump to interrupt vector.
-     * 3. The register value change in Step 1 may happen during Step 2.
-     *
-     * To prevent this, here a fence is used
      */
-    rv_utils_memory_barrier();
+    REG_READ(CLIC_INT_THRESH_REG);
     RV_SET_CSR(mstatus, old_mstatus & MSTATUS_MIE);
 
     return old_thresh;