feat[serial][v2]: add RX DMA event mode control

add serial v2 RX DMA event mode configuration for DMA-enabled builds
support STM32 UART RX DMA half/full transfer interrupt policy selection
validate RX DMA event mode before applying serial configuration
restore serial configuration when backend configure fails

2 files changed, 67 insertions, 19 deletions

diff --git a/components/drivers/include/drivers/dev_serial_v2.h b/components/drivers/include/drivers/dev_serial_v2.h
index b987bc4543..2a8d9145e6 100644
--- a/components/drivers/include/drivers/dev_serial_v2.h
+++ b/components/drivers/include/drivers/dev_serial_v2.h
@@ -225,21 +225,37 @@
 #define RT_SERIAL_FLOWCONTROL_CTSRTS    1
 #define RT_SERIAL_FLOWCONTROL_NONE      0
 
+#ifdef RT_SERIAL_USING_DMA
+/**
+ * @brief Serial RX DMA data event mode.
+ * @note This mode controls only DMA half/full transfer data events.
+ *       UART IDLE interrupt remains enabled in RX DMA mode.
+ */
+enum rt_serial_rx_dma_event_mode
+{
+    RT_SERIAL_RX_DMA_EVENT_AUTO = 0,  /**< Use the default RX DMA event mode. */
+    RT_SERIAL_RX_DMA_EVENT_NONE,      /**< Disable DMA half/full data events; UART IDLE still reports received data. */
+    RT_SERIAL_RX_DMA_EVENT_FULL_ONLY, /**< Report only DMA transfer-complete data events plus UART IDLE. */
+    RT_SERIAL_RX_DMA_EVENT_HALF_FULL  /**< Report both DMA half-transfer and transfer-complete data events plus UART IDLE. */
+};
+#endif /* RT_SERIAL_USING_DMA */
+
 /* Default config for serial_configure structure */
 #ifdef RT_SERIAL_USING_DMA
-#define RT_SERIAL_CONFIG_DEFAULT                      \
-{                                                     \
-    BAUD_RATE_115200,           /* 115200 bits/s */   \
-    DATA_BITS_8,                /* 8 databits */      \
-    STOP_BITS_1,                /* 1 stopbit */       \
-    PARITY_NONE,                /* No parity  */      \
-    BIT_ORDER_LSB,              /* LSB first sent */  \
-    NRZ_NORMAL,                 /* Normal mode */     \
-    RT_SERIAL_RX_MINBUFSZ,      /* rxBuf size */      \
-    RT_SERIAL_TX_MINBUFSZ,      /* txBuf size */      \
-    RT_SERIAL_FLOWCONTROL_NONE, /* Off flowcontrol */ \
-    0,                          /* reserved */        \
-    RT_SERIAL_RX_MINBUFSZ / 2,  /* dma_ping_bufsz */  \
+#define RT_SERIAL_CONFIG_DEFAULT                         \
+{                                                        \
+    BAUD_RATE_115200,             /* 115200 bits/s */    \
+    DATA_BITS_8,                  /* 8 databits */       \
+    STOP_BITS_1,                  /* 1 stopbit */        \
+    PARITY_NONE,                  /* No parity  */       \
+    BIT_ORDER_LSB,                /* LSB first sent */   \
+    NRZ_NORMAL,                   /* Normal mode */      \
+    RT_SERIAL_RX_MINBUFSZ,        /* rxBuf size */       \
+    RT_SERIAL_TX_MINBUFSZ,        /* txBuf size */       \
+    RT_SERIAL_FLOWCONTROL_NONE,   /* Off flowcontrol */  \
+    0,                            /* reserved */         \
+    RT_SERIAL_RX_MINBUFSZ / 2,    /* dma_ping_bufsz */   \
+    RT_SERIAL_RX_DMA_EVENT_AUTO,  /* rx dma event mode */ \
 }
 #else
 #define RT_SERIAL_CONFIG_DEFAULT                      \
@@ -255,7 +271,7 @@
     RT_SERIAL_FLOWCONTROL_NONE, /* Off flowcontrol */ \
     0,                          /* reserved */        \
 }
-#endif
+#endif /* RT_SERIAL_USING_DMA */
 
 /**
  * @brief Serial receive indicate hook function type
@@ -280,7 +296,8 @@ struct serial_configure
 
 #ifdef RT_SERIAL_USING_DMA
     rt_uint32_t dma_ping_bufsz          :16;
-#endif
+    enum rt_serial_rx_dma_event_mode rx_dma_event_mode; /**< RX DMA half/full data event mode. */
+#endif /* RT_SERIAL_USING_DMA */
 };
 
 /**
diff --git a/components/drivers/serial/dev_serial_v2.c b/components/drivers/serial/dev_serial_v2.c
index d8cc2e0cb5..e7851f07ea 100644
--- a/components/drivers/serial/dev_serial_v2.c
+++ b/components/drivers/serial/dev_serial_v2.c
@@ -102,7 +102,7 @@ static int serial_fops_open(struct dfs_file *fd)
 
     rt_device_close(device);
     ret = rt_device_open(device, flags);
-    
+
     if (ret == RT_EOK)
     {
         serial = (struct rt_serial_device *)device;
@@ -1388,6 +1388,21 @@ static void _tc_flush(struct rt_serial_device *serial, int queue)
 }
 #endif /* RT_USING_POSIX_TERMIOS */
 
+#ifdef RT_SERIAL_USING_DMA
+/**
+ * @brief Check whether one serial RX DMA event mode value is valid.
+ * @param mode RX DMA event mode value.
+ * @return RT_TRUE if the mode value is valid.
+ */
+static rt_bool_t rt_serial_rx_dma_event_mode_valid(enum rt_serial_rx_dma_event_mode mode)
+{
+    return ((mode == RT_SERIAL_RX_DMA_EVENT_AUTO) ||
+            (mode == RT_SERIAL_RX_DMA_EVENT_NONE) ||
+            (mode == RT_SERIAL_RX_DMA_EVENT_FULL_ONLY) ||
+            (mode == RT_SERIAL_RX_DMA_EVENT_HALF_FULL)) ? RT_TRUE : RT_FALSE;
+}
+#endif /* RT_SERIAL_USING_DMA */
+
 /**
   * @brief Control the serial device.
   * @param dev The pointer of device driver structure
@@ -1425,20 +1440,36 @@ static rt_err_t rt_serial_control(struct rt_device *dev,
         else
         {
             struct serial_configure *pconfig = (struct serial_configure *)args;
+            struct serial_configure old_config = serial->config;
+
+#ifdef RT_SERIAL_USING_DMA
+            if (rt_serial_rx_dma_event_mode_valid(pconfig->rx_dma_event_mode) != RT_TRUE)
+            {
+                ret = -RT_EINVAL;
+                break;
+            }
+#endif /* RT_SERIAL_USING_DMA */
+
             if (((pconfig->rx_bufsz != serial->config.rx_bufsz) || (pconfig->tx_bufsz != serial->config.tx_bufsz)
 #ifdef RT_SERIAL_USING_DMA
                  || (pconfig->dma_ping_bufsz != serial->config.dma_ping_bufsz)
-#endif
+                 || (pconfig->rx_dma_event_mode != serial->config.rx_dma_event_mode)
+#endif /* RT_SERIAL_USING_DMA */
                      ) &&
                 serial->parent.ref_count != 0)
             {
-                /*can not change buffer size*/
+                /* can not change buffer or DMA event configuration while opened */
                 ret = -RT_EBUSY;
                 break;
             }
+
             /* set serial configure */
             serial->config = *pconfig;
-            serial->ops->configure(serial, (struct serial_configure *)args);
+            ret = serial->ops->configure(serial, (struct serial_configure *)args);
+            if (ret != RT_EOK)
+            {
+                serial->config = old_config;
+            }
         }
         break;
     case RT_SERIAL_CTRL_GET_CONFIG: