[GitHub] [incubator-nuttx] pkarashchenko commented on a change in pull request #5541: arch:xtensa: modify svcall to swint

[GitBox <gi...@apache.org>]

pkarashchenko commented on a change in pull request #5541:
URL: https://github.com/apache/incubator-nuttx/pull/5541#discussion_r811907608



##########
File path: arch/xtensa/src/common/xtensa_swint.c
##########
@@ -94,22 +102,90 @@ int xtensa_svcall(int irq, void *context, void *arg)
 
       case SYS_save_context:
         {
+          DEBUGASSERT(regs[REG_A3] != 0);
+          memcpy((uint32_t *)regs[REG_A3], regs, (4 * XCPTCONTEXT_REGS));
+#if XCHAL_CP_NUM > 0
+          cpstate = (uintptr_t)regs[REG_A3] + cpstate_off;
+          xtensa_coproc_savestate((struct xtensa_cpstate_s *)cpstate);
+#endif
+        }
+
+        break;
+
+      /* A2=SYS_restore_context:  This is a restore context command:
+       *
+       * void xtensa_fullcontextrestore(uint32_t *restoreregs)
+       *      noreturn_function;
+       *
+       * At this point, the following values are saved in context:
+       *
+       *   A2 = SYS_restore_context
+       *   A3 = restoreregs
+       *
+       * In this case, we simply need to set CURRENT_REGS to restore
+       * register area referenced in the saved A3. context == CURRENT_REGS
+       * is the normal exception return.  By setting CURRENT_REGS =
+       * context[A3], we force the return to the saved context referenced
+       * in A3.
+       */
+
+      case SYS_restore_context:
+        {
+#if XCHAL_CP_NUM > 0
+          cpstate = (uintptr_t)regs[REG_A3] + cpstate_off;
+          xtensa_coproc_restorestate((struct xtensa_cpstate_s *)cpstate);
+#endif
+          DEBUGASSERT(regs[REG_A3] != 0);
+          CURRENT_REGS = (uint32_t *)regs[REG_A3];
         }
+
+        break;
+
+      /* A2=SYS_switch_context:  This is a switch context command:
+       *
+       * void xtensa_switchcontext
+       *      (uint32_t *saveregs, uint32_t *restoreregs);
+       *
+       * At this point, the following values are saved in context:
+       *
+       *   A2 = SYS_switch_context
+       *   A3 = saveregs
+       *   A4 = restoreregs
+       *
+       * In this case, we do both: We save the context registers to the save
+       * register area reference by the saved contents of A3 and then set
+       * CURRENT_REGS to the save register area referenced by the saved
+       * contents of A4.
+       */
+
+      case SYS_switch_context:
+        {
+          DEBUGASSERT(regs[REG_A3] != 0 && regs[REG_A4] != 0);
+
+          memcpy((uint32_t *)regs[REG_A3], regs, (4 * XCPTCONTEXT_REGS));
+          CURRENT_REGS = (uint32_t *)regs[REG_A4];
+        }
+
         break;
     }
 
+  if (CURRENT_REGS[REG_PS] & PS_EXCM_MASK)

Review comment:
       ```suggestion
     if ((CURRENT_REGS[REG_PS] & PS_EXCM_MASK) != 0)
   ```




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