boards/samv7/common: add support for UART RX DMA polling

This adds the support for RX DMA polling. The board initializes timer channel SAMV7_UART_RXDMA_POLL_TIMER with frequency SAMV7_UART_RXDMA_POLL_FREQUENCY that triggers DMA polling function. Signed-off-by: Michal Lenc <[email protected]>
apache · Jan 29, 2025 · db38122 · db38122
1 parent 8e58b0f
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diff --git a/boards/arm/samv7/common/Kconfig b/boards/arm/samv7/common/Kconfig
@@ -62,6 +62,37 @@ config SAMV7_HSMCI0_MOUNT_MOUNTPOINT
 
 endif # SAMV7_HSMCI0_MOUNT
 
+config SAMV7_UART_RXDMA_POLL
+	bool "Enable U(S)ART RX DMA Polling"
+	default n
+	depends on UART0_RXDMA || UART1_RXDMA || UART2_RXDMA || UART3_RXDMA || \
+	           UART4_RXDMA || USART0_RXDMA || USART1_RXDMA || USART2_RXDMA
+	---help---
+		UART peripheral with RX DMA need periodic polling that checks the received
+		DMA buffers for received bytes that have not accumulated to the point
+		where the DMA interrupt has triggered.
+
+if SAMV7_UART_RXDMA_POLL
+
+config SAMV7_UART_RXDMA_POLL_TIMER
+	int "Timer channel to trigger polling"
+	default 0
+	range 0 11
+	---help---
+		The number of timer channel to trigger the polling. Values from 0 to 11
+		are available. Be careful not to assign the same channel that is
+		already configured to other peripheral (ADC trigger for example).
+
+config SAMV7_UART_RXDMA_POLL_FREQUENCY
+	int "Timer frequency"
+	default 1000
+	---help---
+		Frequency of the timer to trigger the polling. You might want to keep
+		this reasonably low to avoid unnecessary overhead and negate
+		DMA benefit.
+
+endif # SAMV7_UART_RXDMA_POLL
+
 config SAMV7_PROGMEM_OTA_PARTITION
 	bool
 	default n

diff --git a/boards/arm/samv7/common/include/board_uart_rxdma_poll.h b/boards/arm/samv7/common/include/board_uart_rxdma_poll.h
@@ -0,0 +1,110 @@
+/****************************************************************************
+ * boards/arm/samv7/common/include/board_uart_rxdma_poll.h
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * 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 __BOARDS_ARM_SAMV7_COMMON_INCLUDE_BOARD_UART_RXDMA_POLL_H
+#define __BOARDS_ARM_SAMV7_COMMON_INCLUDE_BOARD_UART_RXDMA_POLL_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+#ifndef __ASSEMBLY__
+
+#undef EXTERN
+#if defined(__cplusplus)
+#define EXTERN extern "C"
+extern "C"
+{
+#else
+#define EXTERN extern
+#endif
+
+/****************************************************************************
+ * Public Functions Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: board_uart_rxdma_poll_stop
+ *
+ * Description:
+ *   This function starts the timer polling UART.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+void board_uart_rxdma_poll_start(void);
+
+/****************************************************************************
+ * Name: board_uart_rxdma_poll_stop
+ *
+ * Description:
+ *   This function stops the timer polling UART. No resourses are freed,
+ *   time is just stopped and can be started again.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+void board_uart_rxdma_poll_stop(void);
+
+/****************************************************************************
+ * Name: board_uart_rxdma_poll_init
+ *
+ * Description:
+ *   This function initializes and starts the timer that is polling
+ *   UART/USART peripherals with RX DMA enabled.
+ *
+ * Input Parameters:
+ *   channel   - Channel number (0-11, see TC_CHANx)
+ *   frequency - Timer frequency
+ *
+ * Returned Value:
+ *   0 on success, negative value (errno) on ERROR.
+ *
+ ****************************************************************************/
+
+int board_uart_rxdma_poll_init(int channel, uint32_t frequency);
+
+#undef EXTERN
+#if defined(__cplusplus)
+}
+#endif
+
+#endif /* __ASSEMBLY__ */
+#endif /* __BOARDS_ARM_SAMV7_COMMON_INCLUDE_BOARD_UART_RXDMA_POLL_H */
diff --git a/boards/arm/samv7/common/src/Make.defs b/boards/arm/samv7/common/src/Make.defs
@@ -46,6 +46,10 @@ ifeq ($(CONFIG_SAMV7_GPIO_ENC),y)
 CSRCS += sam_gpio_enc.c
 endif
 
+ifeq ($(CONFIG_SAMV7_UART_RXDMA_POLL),y)
+CSRCS += sam_uart_rxdma_poll.c
+endif
+
 DEPPATH += --dep-path src
 VPATH += :src
 CFLAGS += ${INCDIR_PREFIX}$(TOPDIR)$(DELIM)arch$(DELIM)$(CONFIG_ARCH)$(DELIM)src$(DELIM)board$(DELIM)src

diff --git a/boards/arm/samv7/common/src/sam_uart_rxdma_poll.c b/boards/arm/samv7/common/src/sam_uart_rxdma_poll.c
@@ -0,0 +1,194 @@
+/****************************************************************************
+ * boards/arm/samv7/common/src/sam_uart_rxdma_poll.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * 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 <nuttx/arch.h>
+#include <nuttx/board.h>
+#include <arch/board/board.h>
+
+#include "sam_tc.h"
+#include "sam_serial.h"
+
+#include "board_uart_rxdma_poll.h"
+
+#ifdef CONFIG_SAMV7_UART_RXDMA_POLL
+
+static TC_HANDLE poll_tc;
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: timer_handler
+ *
+ * Description:
+ *   Timer interrupt callback.
+ *
+ * Input Parameters:
+ *   tch - The handle that represents the timer state
+ *   arg - An opaque argument provided when the interrupt was registered
+ *   sr  - The value of the timer interrupt status register at the time
+ *         that the interrupt occurred.
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+static void timer_handler(TC_HANDLE tch, void *arg, uint32_t sr)
+{
+  sam_serial_dma_poll();
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: board_uart_rxdma_poll_stop
+ *
+ * Description:
+ *   This function starts the timer polling UART.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+void board_uart_rxdma_poll_start(void)
+{
+  sam_tc_start(poll_tc);
+}
+
+/****************************************************************************
+ * Name: board_uart_rxdma_poll_stop
+ *
+ * Description:
+ *   This function stops the timer polling UART. No resourses are freed,
+ *   time is just stopped and can be started again.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+void board_uart_rxdma_poll_stop(void)
+{
+  sam_tc_stop(poll_tc);
+}
+
+/****************************************************************************
+ * Name: board_uart_rxdma_poll_init
+ *
+ * Description:
+ *   This function initializes and starts the timer that is polling
+ *   UART/USART peripherals with RX DMA enabled.
+ *
+ * Input Parameters:
+ *   channel   - Channel number (0-11, see TC_CHANx)
+ *   frequency - Timer frequency
+ *
+ * Returned Value:
+ *   0 on success, negative value (errno) on ERROR.
+ *
+ ****************************************************************************/
+
+int board_uart_rxdma_poll_init(int channel, uint32_t frequency)
+{
+  int ret;
+  uint32_t div;
+  uint32_t tcclks;
+  uint32_t actual;
+  uint32_t mode;
+  uint32_t fdiv;
+  uint32_t regval;
+
+  if (channel < TC_CHAN0 || channel > TC_CHAN11)
+    {
+      syslog(LOG_ERR, "Invalid channel number: %d", channel);
+      return -1;
+    }
+
+  ret = sam_tc_clockselect(frequency, &tcclks, &actual);
+  if (ret < 0)
+    {
+      syslog(LOG_ERR, "sam_tc_divisor failed: %d", ret);
+      return ret;
+    }
+
+  div = BOARD_MCK_FREQUENCY / actual;
+
+  /* Set the timer/counter waveform mode the clock input selected by
+   * sam_tc_clockselect()
+   */
+
+  mode = ((tcclks << TC_CMR_TCCLKS_SHIFT) |  /* Use selected TCCLKS value */
+          TC_CMR_WAVSEL_UPRC |               /* UP mode w/ trigger on RC Compare */
+          TC_CMR_WAVE);                      /* Wave mode */
+
+  /* Now allocate and configure the channel */
+
+  poll_tc = sam_tc_allocate(channel, mode);
+  if (!poll_tc)
+    {
+      syslog(LOG_ERR, "Failed to allocate channel %d mode %08" PRIx32 "\n",
+             channel, mode);
+      return -EINVAL;
+    }
+
+  /* The divider returned by sam_tc_clockselect() is the reload value
+   * that will achieve a 1Hz rate.  We need to multiply this to get the
+   * desired frequency.  sam_tc_divisor() should have already assure
+   * that we can do this without overflowing a 32-bit unsigned integer.
+   */
+
+  fdiv = div * frequency;
+  DEBUGASSERT(div > 0 && div <= fdiv); /* Will check for integer overflow */
+
+  /* Calculate the actual counter value from this divider and the tc input
+   * frequency.
+   */
+
+  regval = BOARD_MCK_FREQUENCY / fdiv;
+  sam_tc_setregister(poll_tc, TC_REGC, regval);
+  sam_tc_attach(poll_tc, timer_handler, NULL, TC_INT_CPCS);
+
+  /* And start the timer */
+
+  sam_tc_start(poll_tc);
+
+  return 0;
+}
+
+#endif /* SAMV7_UART_RXDMA_POLL */