[GitHub] [incubator-nuttx] gustavonihei commented on a change in pull request #4586: xtensa/esp32-s2: Adds oneshot device driver support

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

gustavonihei commented on a change in pull request #4586:
URL: https://github.com/apache/incubator-nuttx/pull/4586#discussion_r714261461



##########
File path: arch/xtensa/src/esp32s2/esp32s2_oneshot.c
##########
@@ -0,0 +1,462 @@
+/****************************************************************************
+ * arch/xtensa/src/esp32s2/esp32s2_oneshot.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdint.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/arch.h>
+#include <nuttx/timers/oneshot.h>
+#include <nuttx/clock.h>
+
+#include "hardware/esp32s2_soc.h"
+
+#include "esp32s2_tim.h"
+#include "esp32s2_clockconfig.h"
+#include "esp32s2_oneshot.h"
+
+#ifdef CONFIG_ESP32S2_ONESHOT
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define MAX_TIMER_COUNTER UINT64_MAX
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+static int esp32s2_oneshot_handler(int irq, void * context, void *arg);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: esp32s2_oneshot_handler
+ *
+ * Description:
+ *   Oneshot interrupt Handler. When any oneshot timer interrupt
+ *   expires, this function will be triggered. It will forward the call to
+ *   the next level up.
+ *
+ * Input Parameters:
+ *   irq   - IRQ associated to that interrupt
+ *   arg -   A pointer to the argument provided when the interrupt was
+ *           registered.
+ *
+ * Returned Value:
+ *   Zero on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+static int esp32s2_oneshot_handler(int irq, void * context,
+                                   void *arg)
+{
+  int ret = OK;
+  struct esp32s2_oneshot_s *oneshot =
+    (struct esp32s2_oneshot_s *)arg;
+
+  DEBUGASSERT(oneshot != NULL && oneshot->handler != NULL);
+
+  tmrinfo("Oneshot handler triggered\n");
+
+  /* Stop timer
+   * Note: It's not necessary to disable the alarm because
+   * it automatically disables each time it expires.
+   */
+
+  ESP32S2_TIM_STOP(oneshot->tim);
+
+  /* Disable interrupts */
+
+  ESP32S2_TIM_DISABLEINT(oneshot->tim);
+
+  /* Detach handler */
+
+  ret = ESP32S2_TIM_SETISR(oneshot->tim, NULL, NULL);
+
+  /* Call the callback */
+
+  oneshot->handler((void *)oneshot->arg);
+
+  /* Restore state */
+
+  oneshot->running = false;
+  oneshot->handler = NULL;
+  oneshot->arg = NULL;
+
+  /* Clear the Interrupt */
+
+  ESP32S2_TIM_ACKINT(oneshot->tim);
+
+  return ret;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: esp32s2_oneshot_initialize
+ *
+ * Description:
+ *   Initialize the oneshot timer wrapper.
+ *
+ * Input Parameters:
+ *   oneshot    Caller allocated instance of the oneshot state structure.
+ *   chan       Timer counter channel to be used.
+ *   resolution The required resolution of the timer in units of
+ *              microseconds.  NOTE that the range is restricted to the
+ *              range of uint16_t (excluding zero).
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; a negated errno value is returned
+ *   on failure.
+ *
+ ****************************************************************************/
+
+int esp32s2_oneshot_initialize(struct esp32s2_oneshot_s *oneshot,
+                               int chan, uint16_t resolution)
+{
+  int ret = OK;
+
+  tmrinfo("chan=%d resolution=%d usecs\n", chan, resolution);
+
+  DEBUGASSERT(oneshot != NULL);
+  DEBUGASSERT(resolution > 0);
+
+  oneshot->chan = chan;
+
+  oneshot->tim = esp32s2_tim_init(chan);
+  if (oneshot->tim == NULL)
+    {
+      tmrerr("ERROR: Failed to allocate TIM %d\n", chan);
+      ret = -EBUSY;
+    }
+  else
+    {
+      uint16_t pre;
+
+      /* Initialize the remaining fields in the state structure. */
+
+      oneshot->running    = false;
+      oneshot->handler    = NULL;
+      oneshot->arg        = NULL;
+      oneshot->resolution = resolution;
+
+      /* Ensure timer is disabled.
+       * Change the prescaler divider with the timer enabled can lead to
+       * unpredictable results.
+       */
+
+      ESP32S2_TIM_STOP(oneshot->tim);
+
+      ESP32S2_TIM_CLK_SRC(oneshot->tim, ESP32S2_TIM_APB_CLK);
+
+      /* Calculate the suitable prescaler according to the current apb
+       * frequency to generate a period equals to resolution.
+       */
+
+      pre = (esp_clk_apb_freq() * resolution) / USEC_PER_SEC;
+
+      /* Configure TIMER prescaler */
+
+      ESP32S2_TIM_SETPRE(oneshot->tim, pre);
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: esp32s2_oneshot_max_delay
+ *
+ * Description:
+ *   Return the maximum delay supported by the timer.
+ *
+ * Input Parameters:
+ *   oneshot Caller allocated instance of the oneshot state structure. This
+ *           structure must have been previously initialized via a call to
+ *           esp32s2_oneshot_initialize();
+ *   usec    The maximum delay in us.

Review comment:
       ```suggestion
    *
    * Output Parameters:
    *   usec    The maximum delay in us.
   ```
   `usec`is an output parameter here.




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