drivers/tty/serial/imx_earlycon.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Copyright 2020 NXP
   4  */
   5
   6 #include <linux/module.h>
   7 #include <linux/ioport.h>
   8 #include <linux/init.h>
   9 #include <linux/serial_core.h>
  10 #include <linux/serial.h>
  11 #include <linux/delay.h>
  12 #include <linux/of.h>
  13 #include <linux/io.h>
  14
  15 #define URTX0 0x40 /* Transmitter Register */
  16 #define UTS_TXFULL (1<<4) /* TxFIFO full */
  17 #define IMX21_UTS 0xb4 /* UART Test Register on all other i.mx*/
  18
  19 static void imx_uart_console_early_putchar(struct uart_port *port, int ch)
  20 {
  21         while (readl_relaxed(port->membase + IMX21_UTS) & UTS_TXFULL)
  22                 cpu_relax();
  23
  24         writel_relaxed(ch, port->membase + URTX0);
  25 }
  26
  27 static void imx_uart_console_early_write(struct console *con, const char *s,
  28                                          unsigned count)
  29 {
  30         struct earlycon_device *dev = con->data;
  31
  32         uart_console_write(&dev->port, s, count, imx_uart_console_early_putchar);
  33 }
  34
  35 static int __init
  36 imx_console_early_setup(struct earlycon_device *dev, const char *opt)
  37 {
  38         if (!dev->port.membase)
  39                 return -ENODEV;
  40
  41         dev->con->write = imx_uart_console_early_write;
  42
  43         return 0;
  44 }
  45 OF_EARLYCON_DECLARE(ec_imx6q, "fsl,imx6q-uart", imx_console_early_setup);
  46 OF_EARLYCON_DECLARE(ec_imx21, "fsl,imx21-uart", imx_console_early_setup);
  47
  48 MODULE_AUTHOR("NXP");
  49 MODULE_DESCRIPTION("IMX earlycon driver");
  50 MODULE_LICENSE("GPL");