drivers/tty/serial/pch_uart.c: add console support

Add console support to pch_uart.  To enable append e.g.
console=ttyPCH0,115200 to your kernel command line.

This is not expected work on CM-iTC boards due to their having a different
clock.

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 159 insertions, 1 deletions

diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index 21febef926a..b950d059a78 100644
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -25,6 +25,9 @@
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/dmi.h>
+#include <linux/console.h>
+#include <linux/nmi.h>
+#include <linux/delay.h>
 
 #include <linux/dmaengine.h>
 #include <linux/pch_dma.h>
@@ -198,6 +201,10 @@ enum {
 
 #define PCI_VENDOR_ID_ROHM              0x10DB
 
+#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
+
+#define DEFAULT_BAUD_RATE 1843200 /* 1.8432MHz */
+
 struct pch_uart_buffer {
         unsigned char *buf;
         int size;
@@ -272,6 +279,9 @@ static struct pch_uart_driver_data drv_dat[] = {
         [pch_ml7223_uart1] = {PCH_UART_2LINE, 1},
 };
 
+#ifdef CONFIG_SERIAL_PCH_UART_CONSOLE
+static struct eg20t_port *pch_uart_ports[PCH_UART_NR];
+#endif
 static unsigned int default_baud = 9600;
 static const int trigger_level_256[4] = { 1, 64, 128, 224 };
 static const int trigger_level_64[4] = { 1, 16, 32, 56 };
@@ -1380,6 +1390,143 @@ static struct uart_ops pch_uart_ops = {
         .verify_port = pch_uart_verify_port
 };
 
+#ifdef CONFIG_SERIAL_PCH_UART_CONSOLE
+
+/*
+ *      Wait for transmitter & holding register to empty
+ */
+static void wait_for_xmitr(struct eg20t_port *up, int bits)
+{
+        unsigned int status, tmout = 10000;
+
+        /* Wait up to 10ms for the character(s) to be sent. */
+        for (;;) {
+                status = ioread8(up->membase + UART_LSR);
+
+                if ((status & bits) == bits)
+                        break;
+                if (--tmout == 0)
+                        break;
+                udelay(1);
+        }
+
+        /* Wait up to 1s for flow control if necessary */
+        if (up->port.flags & UPF_CONS_FLOW) {
+                unsigned int tmout;
+                for (tmout = 1000000; tmout; tmout--) {
+                        unsigned int msr = ioread8(up->membase + UART_MSR);
+                        if (msr & UART_MSR_CTS)
+                                break;
+                        udelay(1);
+                        touch_nmi_watchdog();
+                }
+        }
+}
+
+static void pch_console_putchar(struct uart_port *port, int ch)
+{
+        struct eg20t_port *priv =
+                container_of(port, struct eg20t_port, port);
+
+        wait_for_xmitr(priv, UART_LSR_THRE);
+        iowrite8(ch, priv->membase + PCH_UART_THR);
+}
+
+/*
+ *      Print a string to the serial port trying not to disturb
+ *      any possible real use of the port...
+ *
+ *      The console_lock must be held when we get here.
+ */
+static void
+pch_console_write(struct console *co, const char *s, unsigned int count)
+{
+        struct eg20t_port *priv;
+
+        unsigned long flags;
+        u8 ier;
+        int locked = 1;
+
+        priv = pch_uart_ports[co->index];
+
+        touch_nmi_watchdog();
+
+        local_irq_save(flags);
+        if (priv->port.sysrq) {
+                /* serial8250_handle_port() already took the lock */
+                locked = 0;
+        } else if (oops_in_progress) {
+                locked = spin_trylock(&priv->port.lock);
+        } else
+                spin_lock(&priv->port.lock);
+
+        /*
+         *      First save the IER then disable the interrupts
+         */
+        ier = ioread8(priv->membase + UART_IER);
+
+        pch_uart_hal_disable_interrupt(priv, PCH_UART_HAL_ALL_INT);
+
+        uart_console_write(&priv->port, s, count, pch_console_putchar);
+
+        /*
+         *      Finally, wait for transmitter to become empty
+         *      and restore the IER
+         */
+        wait_for_xmitr(priv, BOTH_EMPTY);
+        iowrite8(ier, priv->membase + UART_IER);
+
+        if (locked)
+                spin_unlock(&priv->port.lock);
+        local_irq_restore(flags);
+}
+
+static int __init pch_console_setup(struct console *co, char *options)
+{
+        struct uart_port *port;
+        int baud = 9600;
+        int bits = 8;
+        int parity = 'n';
+        int flow = 'n';
+
+        /*
+         * Check whether an invalid uart number has been specified, and
+         * if so, search for the first available port that does have
+         * console support.
+         */
+        if (co->index >= PCH_UART_NR)
+                co->index = 0;
+        port = &pch_uart_ports[co->index]->port;
+
+        if (!port || (!port->iobase && !port->membase))
+                return -ENODEV;
+
+        /* setup uartclock */
+        port->uartclk = DEFAULT_BAUD_RATE;
+
+        if (options)
+                uart_parse_options(options, &baud, &parity, &bits, &flow);
+
+        return uart_set_options(port, co, baud, parity, bits, flow);
+}
+
+static struct uart_driver pch_uart_driver;
+
+static struct console pch_console = {
+        .name           = PCH_UART_DRIVER_DEVICE,
+        .write          = pch_console_write,
+        .device         = uart_console_device,
+        .setup          = pch_console_setup,
+        .flags          = CON_PRINTBUFFER | CON_ANYTIME,
+        .index          = -1,
+        .data           = &pch_uart_driver,
+};
+
+#define PCH_CONSOLE     (&pch_console)
+#else
+#define PCH_CONSOLE     NULL
+#endif
+
 static struct uart_driver pch_uart_driver = {
         .owner = THIS_MODULE,
         .driver_name = KBUILD_MODNAME,
@@ -1387,6 +1534,7 @@ static struct uart_driver pch_uart_driver = {
         .major = 0,
         .minor = 0,
         .nr = PCH_UART_NR,
+        .cons = PCH_CONSOLE,
 };
 
 static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
@@ -1413,7 +1561,7 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
         if (!rxbuf)
                 goto init_port_free_txbuf;
 
-        base_baud = 1843200; /* 1.8432MHz */
+        base_baud = DEFAULT_BAUD_RATE;
 
         /* quirk for CM-iTC board */
         board_name = dmi_get_system_info(DMI_BOARD_NAME);
@@ -1463,6 +1611,9 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
         pci_set_drvdata(pdev, priv);
         pch_uart_hal_request(pdev, fifosize, base_baud);
 
+#ifdef CONFIG_SERIAL_PCH_UART_CONSOLE
+        pch_uart_ports[board->line_no] = priv;
+#endif
         ret = uart_add_one_port(&pch_uart_driver, &priv->port);
         if (ret < 0)
                 goto init_port_hal_free;
@@ -1470,6 +1621,9 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
         return priv;
 
 init_port_hal_free:
+#ifdef CONFIG_SERIAL_PCH_UART_CONSOLE
+        pch_uart_ports[board->line_no] = NULL;
+#endif
         free_page((unsigned long)rxbuf);
 init_port_free_txbuf:
         kfree(priv);
@@ -1492,6 +1646,10 @@ static void pch_uart_pci_remove(struct pci_dev *pdev)
         priv = (struct eg20t_port *)pci_get_drvdata(pdev);
 
         pci_disable_msi(pdev);
+
+#ifdef CONFIG_SERIAL_PCH_UART_CONSOLE
+        pch_uart_ports[priv->port.line] = NULL;
+#endif
         pch_uart_exit_port(priv);
         pci_disable_device(pdev);
         kfree(priv);