Merge pull request #16637 from maribu/tests/periph_uart_mode

tests/periph_uart_mode: Drop dep to periph_timer
RIOT-OS · Jul 14, 2021 · f877886 · f877886
2 parents 9ca9efd + ca7c126
commit f877886
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Showing 3 changed files with 26 additions and 3 deletions.
diff --git a/tests/periph_uart_mode/Makefile b/tests/periph_uart_mode/Makefile
@@ -2,8 +2,7 @@ include ../Makefile.tests_common
 
 FEATURES_REQUIRED += periph_uart
 FEATURES_REQUIRED += periph_uart_modecfg
-
-USEMODULE += xtimer
+FEATURES_OPTIONAL += periph_timer
 
 # Set this to prevent welcome message from printing and confusing output
 CFLAGS+=-DLOG_LEVEL=LOG_NONE

diff --git a/tests/periph_uart_mode/Makefile.board.dep b/tests/periph_uart_mode/Makefile.board.dep
@@ -0,0 +1,3 @@
+ifneq (,$(filter periph_timer,$(FEATURES_USED)))
+  USEMODULE += xtimer
+endif
diff --git a/tests/periph_uart_mode/main.c b/tests/periph_uart_mode/main.c
@@ -22,7 +22,9 @@
 #include <string.h>
 #include <stdlib.h>
 
+#include "board.h"
 #include "periph/uart.h"
+#include "periph_conf.h"
 #include "stdio_uart.h"
 #include "xtimer.h"
 
@@ -52,6 +54,25 @@
 /* Stores each mode string for printing at the end of the test */
 static char mode_strings[TOTAL_OPTIONS][MODE_STR_LEN];
 
+static void _delay(void)
+{
+    if (IS_USED(MODULE_XTIMER)) {
+        xtimer_usleep(DELAY_US);
+    }
+    else {
+        /*
+         * As fallback for freshly ported boards with no timer drivers written
+         * yet, we just use the CPU to delay execution and assume that roughly
+         * 20 CPU cycles are spend per loop iteration.
+         *
+         * Note that the volatile qualifier disables compiler optimizations for
+         * all accesses to the counter variable. Without volatile, modern
+         * compilers would detect that the loop is only wasting CPU cycles and
+         * optimize it out - but here the wasting of CPU cycles is desired.
+         */
+        for (volatile uint32_t i = 0; i < CLOCK_CORECLOCK / 20; i++) { }
+    }
+}
 
 static void _get_mode(const uart_data_bits_t data_bits,
                       const uart_parity_t parity, const uart_stop_bits_t stop_bits, char* mode_str) {
@@ -153,7 +174,7 @@ int main(void)
                 if (status == UART_OK) {
                     results[ridx] = true;
                     printf("%s\n", mode_strings[ridx]);
-                    xtimer_usleep(DELAY_US);
+                    _delay();
                 }
                 else {
                     results[ridx] = false;