atxmega: Created an initial implementation of breakpoint-based halt_r…

…esume

src/target/atxmega.c

@@ -503,6 +503,26 @@ static void atxmega_halt_resume(target_s *const target, const bool step)
 			continue;
 		pdi->halt_reason = TARGET_HALT_STEPPING;
 	} else {
+		/*
+		 * To resume the processor we go through the following specific steps:
+		 * Write the program counter to ensure we start where we expect
+		 * Then we release the externally (PDI) applied reset
+		 * We then poke the debug control register to indicate debug-supervised run
+		 * Ensure that PDI is still in debug mode (r4 = 1)
+		 * Read r3 to see that the processor is resuming
+		 */
+		/* Check that we are in administrative halt */
+		if (avr_pdi_reg_read(pdi, PDI_REG_R3) != 0x04U ||
+			/* Try to configure the breakpoints */
+			!atxmega_config_breakpoints(pdi, step) || avr_pdi_reg_read(pdi, PDI_REG_R3) != 0x04U ||
+			/* Set the program counter and release reset */
+			!avr_pdi_write(pdi, PDI_DATA_32, ATXMEGA_DBG_PC, pdi->program_counter) ||
+			!avr_pdi_reg_write(pdi, PDI_REG_RESET, 0U) ||
+			/* Configure the debug controller */
+			!avr_pdi_write(pdi, PDI_DATA_8, ATXMEGA_DBG_CTRL, 0U) || avr_pdi_reg_read(pdi, PDI_REG_R3) != 0x04U ||
+			/* And try to execute the request */
+			!avr_pdi_reg_write(pdi, PDI_REG_R4, 1U))
+			raise_exception(EXCEPTION_ERROR, "Error resuming device, device in incorrect state");
 		pdi->halt_reason = TARGET_HALT_RUNNING;
 	}
 }