drivers/periph: Add timer_poll feature and timer_poll_channel function

cpu/nrf5x_common/Kconfig

@@ -20,6 +20,7 @@ depends on !CPU_FAM_NRF53
     select HAS_PERIPH_HWRNG
     select HAS_PERIPH_TEMPERATURE
     select HAS_PERIPH_TIMER_PERIODIC
+    select HAS_PERIPH_TIMER_POLL
     select HAS_PERIPH_TIMER_QUERY_FREQS
     select HAS_PERIPH_RTT_OVERFLOW
     select HAS_PERIPH_UART_MODECFG

cpu/nrf5x_common/Makefile.features

@@ -5,6 +5,7 @@ FEATURES_PROVIDED += periph_flashpage_in_address_space
 FEATURES_PROVIDED += periph_flashpage_pagewise
 FEATURES_PROVIDED += periph_gpio periph_gpio_irq
 FEATURES_PROVIDED += periph_timer_periodic
+FEATURES_PROVIDED += periph_timer_poll
 FEATURES_PROVIDED += periph_timer_query_freqs
 FEATURES_PROVIDED += periph_uart_modecfg
 FEATURES_PROVIDED += periph_wdt periph_wdt_cb

cpu/nrf5x_common/include/timer_arch.h

@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2015 Jan Wagner <mail@jwagner.eu>
+ *               2015-2016 Freie Universität Berlin
+ *               2019 Inria
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     cpu_nrf5x_common
+ * @ingroup     drivers_periph_timer
+ * @{
+ *
+ * @file
+ * @brief       CPU specific part of the timer API
+ *
+ * @author      Christian Amsüss <chrysn@fsfe.org>
+ */
+
+#ifndef TIMER_ARCH_H
+#define TIMER_ARCH_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef DOXYGEN /* hide implementation specific details from Doxygen */
+
+static inline bool timer_poll_channel(tim_t tim, int channel)
+{
+    return timer_config[tim].dev->EVENTS_COMPARE[channel];
+}
+
+#endif /* DOXYGEN */
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* TIMER_ARCH_H */
+/** @} */

drivers/include/periph/timer.h

@@ -35,6 +35,7 @@
 
 #include <limits.h>
 #include <stdint.h>
+#include <stdbool.h>
 
 #include "architecture.h"
 #include "periph_cpu.h"
@@ -295,6 +296,39 @@ uword_t timer_query_channel_numof(tim_t dev);
  */
 uint32_t timer_query_freqs(tim_t dev, uword_t index);
 
+#if defined(DOXYGEN)
+/**
+ * @brief Check whether a compare channel has matched
+ *
+ * @return true once after the channel has matched.
+ *
+ * It is currently not defined whether this keeps returning true after a
+ * channel has been polled until that channel is set, or whether later calls
+ * return false.
+ *
+ * This is typically used in spin loops that wait for a timer's completion:
+ *
+ * ~~~
+ * while (!timer_poll_channel(tim, chan)) {};
+ * ~~~
+ *
+ * This function is only available on platforms that implement the
+ * `periph_timer_poll` peripheral in addition to `periph_timer`.
+ *
+ */
+/* As this function is polled, it needs to be inlined, so it is typically
+ * provided through timer_arch.h. If a platform ever does not need to go
+ * through static inline here, this declaration's condition can be extended to
+ * be `(defined(MODULE_PERIPH_TIMER_POLL) &&
+ * !defined(PERIPH_TIMER_PROVIDES_INLINE_POLL_CHANNEL) || defined(DOXYGEN)` or
+ * similar. */
+bool timer_poll_channel(tim_t dev, int channel);
+#endif
+
+#if defined(MODULE_PERIPH_TIMER_POLL)
+#include "timer_arch.h"
+#endif
+
 #ifdef __cplusplus
 }
 #endif

kconfigs/Kconfig.features

@@ -572,6 +572,12 @@ config HAS_PERIPH_TIMER_PERIODIC
         Indicates that the Timer peripheral provides the periodic timeout
         functionality.
 
+config HAS_PERIPH_TIMER_POLL
+    bool
+    help
+        Indicates that the Timer peripheral supports the timer_poll_channel
+        function.
+
 config HAS_PERIPH_TIMER_QUERY_FREQS
     bool
     help