tests/drivers uart_mix_fifo_poll: Allow configuring test length

This test is quite heavy and long in simulation,
but its length is meant to find unlikely issues which
may be triggered only very rarely.
Let's provide a kconfig value to chose how long the
test is, and set it to a lower value when running in simulation
(in CI) to save time.

Signed-off-by: Alberto Escolar Piedras <[email protected]>

Author: aescolar

tests/drivers/uart/uart_mix_fifo_poll/Kconfig

@@ -0,0 +1,15 @@
+# Copyright (c) 2024 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+config STRESS_TEST_REPS
+	int "Number of loops in the stress test"
+	# For the simulated devices, which are run by default in CI, we set it to less to not spend too
+	# much CI time
+	default 500 if SOC_SERIES_BSIM_NRFXX
+	default 10000
+	help
+	  For how many loops will the stress test run. The higher this number the longer the
+	  test and therefore the higher likelihood an unlikely race/event will be triggered.
+
+# Include Zephyr's Kconfig
+source "Kconfig"

tests/drivers/uart/uart_mix_fifo_poll/src/main.c

@@ -264,6 +264,7 @@ static void int_async_thread_func(void *p_data, void *base, void *range)
 
 			int idx = data->cnt & 0xF;
 			size_t len = (idx < BUF_SIZE / 2) ? 5 : 1; /* Try various lengths */
+			len = MIN(len, data->max - data->cnt);
 
 			data->cnt += len;
 			err = uart_tx(uart_dev, &int_async_data.buf[idx],
@@ -317,7 +318,7 @@ static void init_test_data(struct test_data *data, const uint8_t *buf, int repea
 
 ZTEST(uart_mix_fifo_poll, test_mixed_uart_access)
 {
-	int repeat = 10000;
+	int repeat = CONFIG_STRESS_TEST_REPS;
 	int err;
 	int num_of_contexts = ARRAY_SIZE(test_data);