arch/arm/samv7: initial support for LIN bus communication

Signed-off-by: Petro Karashchenko <petro.karashchenko@gmail.com>
Co-authored-by: Petro Karashchenko <petro.karashchenko@gmail.com>

arch/arm/src/samv7/hardware/sam_uart.h

@@ -248,7 +248,7 @@
 #define UART_CR_STTBRK               (1 << 9)  /* Bit 9:  Start Break (USART, UART mode only) */
 #define UART_CR_STPBRK               (1 << 10) /* Bit 10: Stop Break (USART, UART mode only) */
 #define UART_CR_STTTO                (1 << 11) /* Bit 11: Start Time-out (USART, UART mode only) */
-#define UART_CR_REQCLR               (1 << 12) /* Bit 12:Request Clear (UART only) */
+#define UART_CR_REQCLR               (1 << 12) /* Bit 12: Request Clear (UART only) */
 #define UART_CR_SENDA                (1 << 12) /* Bit 12: Send Address (USART, UART mode only) */
 #define UART_CR_RETTO                (1 << 15) /* Bit 15: Rearm Time-out (USART, UART mode only) */
 #define UART_CR_RTSEN                (1 << 18) /* Bit 18: Request to Send Enable (USART, UART mode only) */
@@ -266,6 +266,8 @@
 #  define UART_MR_MODE_RS485         (1  << UART_MR_MODE_SHIFT) /* RS485 */
 #  define UART_MR_MODE_HWHS          (2  << UART_MR_MODE_SHIFT) /* Hardware Handshaking */
 #  define UART_MR_MODE_LON           (9  << UART_MR_MODE_SHIFT) /* LON */
+#  define UART_MR_MODE_LINMSTR       (10 << UART_MR_MODE_SHIFT) /* LIN Master */
+#  define UART_MR_MODE_LINSLV        (11 << UART_MR_MODE_SHIFT) /* LIN Slave */
 #  define UART_MR_MODE_SPIMSTR       (14 << UART_MR_MODE_SHIFT) /* SPI Master (SPI mode only) */
 #  define UART_MR_MODE_SPISLV        (15 << UART_MR_MODE_SHIFT) /* SPI Slave (SPI mode only) */
 

arch/arm/src/samv7/sam_serial.c

@@ -1040,11 +1040,9 @@ static int sam_interrupt(int irq, void *context, FAR void *arg)
 
 static int sam_ioctl(struct file *filep, int cmd, unsigned long arg)
 {
-#if defined(CONFIG_SERIAL_TERMIOS) || defined(CONFIG_SERIAL_TIOCSERGSTRUCT)
   struct inode      *inode = filep->f_inode;
   struct uart_dev_s *dev   = inode->i_private;
-#endif
+  int                ret   = OK;
-  int                ret    = OK;
 
   switch (cmd)
     {
@@ -1223,6 +1221,62 @@ static int sam_ioctl(struct file *filep, int cmd, unsigned long arg)
       break;
 #endif /* CONFIG_SERIAL_TERMIOS */
 
+    case TIOCSLINID:
+      {
+        /* Switch USART to LIN mode -> Set identifier register -> This will
+         * issue a LIN header -> Restore USART mode
+         */
+
+        struct sam_dev_s *priv = (struct sam_dev_s *)dev->priv;
+        uint32_t regvalsave = 0;
+        uint32_t regval = 0;
+
+        /* Save actual configuration */
+
+        regvalsave = sam_serialin(priv, SAM_UART_MR_OFFSET);
+
+        /* Issue a LIN header (Master mode only) */
+
+        regval  = regvalsave & ~UART_MR_MODE_MASK;
+        regval |= UART_MR_MODE_LINMSTR;
+        sam_serialout(priv, SAM_UART_MR_OFFSET, regval);
+
+        /* Reset transaction status bits */
+
+        sam_serialout(priv, SAM_UART_CR_OFFSET, UART_CR_RSTSTA);
+
+        /* Write LIN ID to trigger header transmission */
+
+        regval = UART_LINIR_MASK & (uint8_t)arg;
+        sam_serialout(priv, SAM_UART_LINIR_OFFSET, regval);
+
+        /* Wait until the header is on the wire */
+
+        do
+          {
+            /* Header takes 34 bits to transmit so poll with 34 / 4 = 8 bits
+             * cycle time
+             *
+             * TODO: Interrupt + semaphore can be used instead of busy
+             * waiting to improve CPU utilization
+             */
+
+            usleep((8 * 1000 * 1000) / priv->baud);
+
+            regval = sam_serialin(priv, SAM_UART_SR_OFFSET);
+          }
+        while ((regval & UART_INT_LINID) == 0);
+
+        /* Reset transaction status bits */
+
+        sam_serialout(priv, SAM_UART_CR_OFFSET, UART_CR_RSTSTA);
+
+        /* Restore USART mode */
+
+        sam_serialout(priv, SAM_UART_MR_OFFSET, regvalsave);
+      }
+      break;
+
     default:
       ret = -ENOTTY;
       break;

include/nuttx/serial/tioctl.h

@@ -197,6 +197,10 @@
 
 #define SER_SWAP_ENABLED   (1 << 0) /* Enable/disable RX/TX swap */
 
+/* LIN Protocol Support */
+
+#define TIOCSLINID      _TIOC(0x0037) /* Master send one LIN header with specified LIN identifier: uint8_t */
+
 /****************************************************************************
  * Public Type Definitions
  ****************************************************************************/