drivers/tty/serial/owl-uart.c

   1 /*
   2  * Actions Semi Owl family serial console
   3  *
   4  * Copyright 2013 Actions Semi Inc.
   5  * Author: Actions Semi, Inc.
   6  *
   7  * Copyright (c) 2016-2017 Andreas Färber
   8  *
   9  * This program is free software; you can redistribute  it and/or modify it
  10  * under  the terms of  the GNU General  Public License as published by the
  11  * Free Software Foundation;  either version 2 of the  License, or (at your
  12  * option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  21  */
  22
  23 #include <linux/console.h>
  24 #include <linux/delay.h>
  25 #include <linux/io.h>
  26 #include <linux/module.h>
  27 #include <linux/of.h>
  28 #include <linux/platform_device.h>
  29 #include <linux/serial.h>
  30 #include <linux/serial_core.h>
  31
  32 #define OWL_UART_CTL    0x000
  33 #define OWL_UART_TXDAT  0x008
  34 #define OWL_UART_STAT   0x00c
  35
  36 #define OWL_UART_CTL_TRFS_TX            BIT(14)
  37 #define OWL_UART_CTL_EN                 BIT(15)
  38 #define OWL_UART_CTL_RXIE               BIT(18)
  39 #define OWL_UART_CTL_TXIE               BIT(19)
  40
  41 #define OWL_UART_STAT_RIP               BIT(0)
  42 #define OWL_UART_STAT_TIP               BIT(1)
  43 #define OWL_UART_STAT_TFFU              BIT(6)
  44 #define OWL_UART_STAT_TRFL_MASK         (0x1f << 11)
  45 #define OWL_UART_STAT_UTBB              BIT(17)
  46
  47 static inline void owl_uart_write(struct uart_port *port, u32 val, unsigned int off)
  48 {
  49         writel(val, port->membase + off);
  50 }
  51
  52 static inline u32 owl_uart_read(struct uart_port *port, unsigned int off)
  53 {
  54         return readl(port->membase + off);
  55 }
  56
  57 #ifdef CONFIG_SERIAL_OWL_CONSOLE
  58
  59 static void owl_console_putchar(struct uart_port *port, int ch)
  60 {
  61         if (!port->membase)
  62                 return;
  63
  64         while (owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TFFU)
  65                 cpu_relax();
  66
  67         owl_uart_write(port, ch, OWL_UART_TXDAT);
  68 }
  69
  70 static void owl_uart_port_write(struct uart_port *port, const char *s,
  71                                 u_int count)
  72 {
  73         u32 old_ctl, val;
  74         unsigned long flags;
  75         int locked;
  76
  77         local_irq_save(flags);
  78
  79         if (port->sysrq)
  80                 locked = 0;
  81         else if (oops_in_progress)
  82                 locked = spin_trylock(&port->lock);
  83         else {
  84                 spin_lock(&port->lock);
  85                 locked = 1;
  86         }
  87
  88         old_ctl = owl_uart_read(port, OWL_UART_CTL);
  89         val = old_ctl | OWL_UART_CTL_TRFS_TX;
  90         /* disable IRQ */
  91         val &= ~(OWL_UART_CTL_RXIE | OWL_UART_CTL_TXIE);
  92         owl_uart_write(port, val, OWL_UART_CTL);
  93
  94         uart_console_write(port, s, count, owl_console_putchar);
  95
  96         /* wait until all contents have been sent out */
  97         while (owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TRFL_MASK)
  98                 cpu_relax();
  99
 100         /* clear IRQ pending */
 101         val = owl_uart_read(port, OWL_UART_STAT);
 102         val |= OWL_UART_STAT_TIP | OWL_UART_STAT_RIP;
 103         owl_uart_write(port, val, OWL_UART_STAT);
 104
 105         owl_uart_write(port, old_ctl, OWL_UART_CTL);
 106
 107         if (locked)
 108                 spin_unlock(&port->lock);
 109
 110         local_irq_restore(flags);
 111 }
 112
 113 static void owl_uart_early_console_write(struct console *co,
 114                                          const char *s,
 115                                          u_int count)
 116 {
 117         struct earlycon_device *dev = co->data;
 118
 119         owl_uart_port_write(&dev->port, s, count);
 120 }
 121
 122 static int __init
 123 owl_uart_early_console_setup(struct earlycon_device *device, const char *opt)
 124 {
 125         if (!device->port.membase)
 126                 return -ENODEV;
 127
 128         device->con->write = owl_uart_early_console_write;
 129
 130         return 0;
 131 }
 132 OF_EARLYCON_DECLARE(owl, "actions,owl-uart",
 133                     owl_uart_early_console_setup);
 134
 135 #endif /* CONFIG_SERIAL_OWL_CONSOLE */