arch/xmc4 Add tickless support

arch/arm/Kconfig

@@ -600,6 +600,7 @@ config ARCH_CHIP_XMC4
 	select ARCH_HAVE_I2CRESET
 	select ARM_HAVE_MPU_UNIFIED
 	select ARMV7M_HAVE_STACKCHECK
+	select ARCH_HAVE_TICKLESS
 	---help---
 		Infineon XMC4xxx(ARM Cortex-M4) architectures
 

arch/arm/src/xmc4/Make.defs

@@ -25,6 +25,7 @@ include armv7-m/Make.defs
 CHIP_CSRCS  = xmc4_allocateheap.c xmc4_clockconfig.c xmc4_clockutils.c
 CHIP_CSRCS += xmc4_clrpend.c xmc4_flash.c xmc4_gpio.c xmc4_irq.c
 CHIP_CSRCS += xmc4_lowputc.c xmc4_serial.c xmc4_start.c xmc4_usic.c
+CHIP_CSRCS += xmc4_ccu4.c
 
 # Configuration-dependent Kinetis files
 
@@ -34,6 +35,8 @@ endif
 
 ifneq ($(CONFIG_SCHED_TICKLESS),y)
 CHIP_CSRCS += xmc4_timerisr.c
+else
+CHIP_CSRCS += xmc4_tickless.c
 endif
 
 ifeq ($(CONFIG_BUILD_PROTECTED),y)

arch/arm/src/xmc4/xmc4_ccu4.c

@@ -0,0 +1,195 @@
+/****************************************************************************
+ * arch/arm/src/xmc4/xmc4_ccu4.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.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * XMC CCU Driver
+ *
+ * For now, this file contains only helper methods mandatory for xmc tickless
+ * feature. Contibutions are welcomed.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <arch/board/board.h>
+
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include "arm_internal.h"
+#include "hardware/xmc4_ccu4.h"
+#include "xmc4_ccu4.h"
+
+#define CCU4_NDIVIDERS 15
+
+static const uint8_t g_log2divider[CCU4_NDIVIDERS] =
+{
+        1,  /* TIMER_CLOCK1 -> div2 */
+        2,  /* TIMER_CLOCK1 -> div4 */
+        3,  /* TIMER_CLOCK2 -> div8 */
+        4,  /* TIMER_CLOCK2 -> div16 */
+        5,  /* TIMER_CLOCK3 -> div32 */
+        6,  /* TIMER_CLOCK3 -> div64 */
+        7,  /* TIMER_CLOCK4 -> div128 */
+        8,  /* TIMER_CLOCK4 -> div256 */
+        9,  /* TIMER_CLOCK4 -> div512 */
+        10, /* TIMER_CLOCK4 -> div1024 */
+        11, /* TIMER_CLOCK4 -> div2048 */
+        12, /* TIMER_CLOCK4 -> div4096 */
+        13, /* TIMER_CLOCK4 -> div8192 */
+        14, /* TIMER_CLOCK4 -> div16384 */
+        15  /* TIMER_CLOCK4 -> div32769 */
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: xmc4_ccu4_divfreq_lookup
+ *
+ * Description:
+ *  Given the TC input frequency (Ftcin) and a divider index, return the
+ *  value of the divided frequency
+ *
+ * Input Parameters:
+ *   ftcin - TC input frequency
+ *   ndx   - Divider index
+ *
+ * Returned Value:
+ *   The divided frequency value
+ *
+ ****************************************************************************/
+
+static uint32_t xmc4_ccu4_divfreq_lookup(uint32_t ftcin, int ndx)
+{
+  return ftcin >> g_log2divider[ndx];
+}
+
+/****************************************************************************
+ * Name: xmc4_ccu4_freqdiv_lookup
+ *
+ * Description:
+ *  Given the TC input frequency (Ftcin) and a divider index, return the
+ *  value of the Ftcin divider.
+ *
+ * Input Parameters:
+ *   ftcin - TC input frequency
+ *   ndx   - Divider index
+ *
+ * Returned Value:
+ *   The Ftcin input divider value
+ *
+ ****************************************************************************/
+
+static int xmc4_ccu4_freqdiv_lookup(uint32_t ftcin, int ndx)
+{
+  return 1 << g_log2divider[ndx];
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: xmc4_ccu4_divisor
+ *
+ * Description:
+ *   Finds the best MCK divisor given the timer frequency and MCK.  The
+ *   result is guaranteed to satisfy the following equation:
+ *
+ *     (Ftcin / (div * 65536)) <= freq <= (Ftcin / dev)
+ *
+ *   where:
+ *     freq  - the desired frequency
+ *     Ftcin - The timer/counter input frequency
+ *     div   - With DIV being the highest possible value.
+ *
+ * Input Parameters:
+ *   frequency  Desired timer frequency.
+ *   div        Divisor value.
+ *   pssiv      PSSIV field value for divisor.
+ *
+ * Returned Value:
+ *   Zero (OK) if a proper divisor has been found, otherwise a negated errno
+ *   value indicating the nature of the failure.
+ *
+ ****************************************************************************/
+
+int xmc4_ccu4_divisor(uint32_t frequency, uint32_t *div, uint32_t *pssiv)
+{
+  uint32_t ftcin = BOARD_CCU_FREQUENCY;
+  int ndx = 0;
+
+  tmrinfo("frequency=%" PRIu32 "\n", frequency);
+
+  /* Satisfy lower bound.  That is, the value of the divider such that:
+   *
+   *   frequency >= (tc_input_frequency * 65536) / divider.
+   */
+
+  while (frequency < (xmc4_ccu4_divfreq_lookup(ftcin, ndx) >> 16))
+    {
+      if (++ndx > CCU4_NDIVIDERS)
+        {
+          /* If no divisor can be found, return -ERANGE */
+
+          tmrerr("ERROR: Lower bound search failed\n");
+          return -ERANGE;
+        }
+    }
+
+  /* Try to maximize DIV while still satisfying upper bound.  That the
+   * value of the divider such that:
+   *
+   *   frequency < tc_input_frequency / divider.
+   */
+
+  for (; ndx < (CCU4_NDIVIDERS - 1); ndx++)
+    {
+      if (frequency > xmc4_ccu4_divfreq_lookup(ftcin, ndx + 1))
+        {
+          break;
+        }
+    }
+
+  /* Return the divider value */
+
+  if (div)
+    {
+      uint32_t value = xmc4_ccu4_freqdiv_lookup(ftcin, ndx);
+      tmrinfo("return div=%lu\n", (unsigned long)value);
+      *div = value;
+    }
+
+  /* Return the PSSIV selection */
+
+  if (pssiv)
+    {
+      tmrinfo("return pssiv=%d\n", ndx + 1);
+      *pssiv = ndx + 1;
+    }
+
+  return OK;
+}

arch/arm/src/xmc4/xmc4_ccu4.h

@@ -0,0 +1,64 @@
+/****************************************************************************
+ * arch/arm/src/xmc4/xmc4_ccu4.h
+ *
+ * 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.
+ *
+ ****************************************************************************/
+
+#ifndef __ARCH_ARM_SRC_XMC4_XMC4_CCU4_H
+#define __ARCH_ARM_SRC_XMC4_XMC4_CCU4_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdint.h>
+#include <stdbool.h>
+
+/****************************************************************************
+ * Public Functions Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: xmc4_ccu4_divisor
+ *
+ * Description:
+ *   Finds the best MCK divisor given the timer frequency and MCK.  The
+ *   result is guaranteed to satisfy the following equation:
+ *
+ *     (Ftcin / (div * 65536)) <= freq <= (Ftcin / dev)
+ *
+ *   where:
+ *     freq  - the desired frequency
+ *     Ftcin - The timer/counter input frequency
+ *     div   - With DIV being the highest possible value.
+ *
+ * Input Parameters:
+ *   frequency  Desired timer frequency.
+ *   div        Divisor value.
+ *   pssiv      PSSIV field value for divisor.
+ *
+ * Returned Value:
+ *   Zero (OK) if a proper divisor has been found, otherwise a negated errno
+ *   value indicating the nature of the failure.
+ *
+ ****************************************************************************/
+
+int xmc4_ccu4_divisor(uint32_t frequency, uint32_t *div, uint32_t *pssiv);
+
+#endif