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![Viresh Kumar](/assets/img/avatar_default.png)
The current driver triggers a lockdep warning for if tty_flip_buffer_push() is
called with uart_port->lock locked. This never shows up on UP kernels and comes
up only on SMP kernels.
Crash looks like this (produced with samsung.c driver):
-----
[<c0014d58>] (unwind_backtrace+0x0/0xf8) from [<c0011908>] (show_stack+0x10/0x14)
[<c0011908>] (show_stack+0x10/0x14) from [<c035da34>] (dump_stack+0x6c/0xac)
[<c035da34>] (dump_stack+0x6c/0xac) from [<c01b59ac>] (do_raw_spin_unlock+0xc4/0xd8)
[<c01b59ac>] (do_raw_spin_unlock+0xc4/0xd8) from [<c03627e4>] (_raw_spin_unlock_irqrestore+0xc/0)
[<c03627e4>] (_raw_spin_unlock_irqrestore+0xc/0x38) from [<c020a1a8>] (s3c24xx_serial_rx_chars+0)
[<c020a1a8>] (s3c24xx_serial_rx_chars+0x12c/0x260) from [<c020aae8>] (s3c64xx_serial_handle_irq+)
[<c020aae8>] (s3c64xx_serial_handle_irq+0x48/0x60) from [<c006aaa0>] (handle_irq_event_percpu+0x)
[<c006aaa0>] (handle_irq_event_percpu+0x50/0x194) from [<c006ac20>] (handle_irq_event+0x3c/0x5c)
[<c006ac20>] (handle_irq_event+0x3c/0x5c) from [<c006d864>] (handle_fasteoi_irq+0x80/0x13c)
[<c006d864>] (handle_fasteoi_irq+0x80/0x13c) from [<c006a4a4>] (generic_handle_irq+0x20/0x30)
[<c006a4a4>] (generic_handle_irq+0x20/0x30) from [<c000f454>] (handle_IRQ+0x38/0x94)
[<c000f454>] (handle_IRQ+0x38/0x94) from [<c0008538>] (gic_handle_irq+0x34/0x68)
[<c0008538>] (gic_handle_irq+0x34/0x68) from [<c00123c0>] (__irq_svc+0x40/0x70)
Exception stack(0xc04cdf70 to 0xc04cdfb8)
df60: 00000000 00000000 0000166e 00000000
df80: c04cc000 c050278f c050278f 00000001 c04d444c 410fc0f4 c03649b0 00000000
dfa0: 00000001 c04cdfb8 c000f758 c000f75c 60070013 ffffffff
[<c00123c0>] (__irq_svc+0x40/0x70) from [<c000f75c>] (arch_cpu_idle+0x28/0x30)
[<c000f75c>] (arch_cpu_idle+0x28/0x30) from [<c0054888>] (cpu_startup_entry+0x5c/0x148)
[<c0054888>] (cpu_startup_entry+0x5c/0x148) from [<c0497aa4>] (start_kernel+0x334/0x38c)
BUG: spinlock lockup suspected on CPU#0, kworker/0:1/360
lock: s3c24xx_serial_ports+0x1d8/0x370, .magic: dead4ead, .owner: <none>/-1, .owner_cpu: -1
CPU: 0 PID: 360 Comm: kworker/0:1 Not tainted 3.11.0-rc6-next-20130819-00003-g75485f1 #2
Workqueue: events flush_to_ldisc
[<c0014d58>] (unwind_backtrace+0x0/0xf8) from [<c0011908>] (show_stack+0x10/0x14)
[<c0011908>] (show_stack+0x10/0x14) from [<c035da34>] (dump_stack+0x6c/0xac)
[<c035da34>] (dump_stack+0x6c/0xac) from [<c01b581c>] (do_raw_spin_lock+0x100/0x17c)
[<c01b581c>] (do_raw_spin_lock+0x100/0x17c) from [<c03628a0>] (_raw_spin_lock_irqsave+0x20/0x28)
[<c03628a0>] (_raw_spin_lock_irqsave+0x20/0x28) from [<c0203224>] (uart_start+0x18/0x34)
[<c0203224>] (uart_start+0x18/0x34) from [<c01ef890>] (__receive_buf+0x4b4/0x738)
[<c01ef890>] (__receive_buf+0x4b4/0x738) from [<c01efb44>] (n_tty_receive_buf2+0x30/0x98)
[<c01efb44>] (n_tty_receive_buf2+0x30/0x98) from [<c01f2ba8>] (flush_to_ldisc+0xec/0x138)
[<c01f2ba8>] (flush_to_ldisc+0xec/0x138) from [<c0031af0>] (process_one_work+0xfc/0x348)
[<c0031af0>] (process_one_work+0xfc/0x348) from [<c0032138>] (worker_thread+0x138/0x37c)
[<c0032138>] (worker_thread+0x138/0x37c) from [<c0037a7c>] (kthread+0xa4/0xb0)
[<c0037a7c>] (kthread+0xa4/0xb0) from [<c000e5f8>] (ret_from_fork+0x14/0x3c)
-----
Release the port lock before calling tty_flip_buffer_push() and reacquire it
after the call.
Similar stuff was already done for few other drivers in the past, like:
commit 2389b27216
Author: Thomas Gleixner <tglx@linutronix.de>
Date: Tue May 29 21:53:50 2007 +0100
[ARM] 4417/1: Serial: Fix AMBA drivers locking
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
482 lines
11 KiB
C
482 lines
11 KiB
C
/*
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* Serial Port driver for a NWP uart device
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*
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* Copyright (C) 2008 IBM Corp., Benjamin Krill <ben@codiert.org>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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*/
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#include <linux/init.h>
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#include <linux/export.h>
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#include <linux/console.h>
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#include <linux/serial.h>
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#include <linux/serial_reg.h>
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#include <linux/serial_core.h>
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#include <linux/tty.h>
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#include <linux/tty_flip.h>
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#include <linux/irqreturn.h>
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#include <linux/mutex.h>
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#include <linux/of_platform.h>
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#include <linux/of_device.h>
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#include <linux/nwpserial.h>
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#include <asm/prom.h>
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#include <asm/dcr.h>
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#define NWPSERIAL_NR 2
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#define NWPSERIAL_STATUS_RXVALID 0x1
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#define NWPSERIAL_STATUS_TXFULL 0x2
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struct nwpserial_port {
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struct uart_port port;
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dcr_host_t dcr_host;
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unsigned int ier;
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unsigned int mcr;
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};
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static DEFINE_MUTEX(nwpserial_mutex);
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static struct nwpserial_port nwpserial_ports[NWPSERIAL_NR];
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static void wait_for_bits(struct nwpserial_port *up, int bits)
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{
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unsigned int status, tmout = 10000;
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/* Wait up to 10ms for the character(s) to be sent. */
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do {
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status = dcr_read(up->dcr_host, UART_LSR);
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if (--tmout == 0)
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break;
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udelay(1);
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} while ((status & bits) != bits);
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}
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#ifdef CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL_CONSOLE
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static void nwpserial_console_putchar(struct uart_port *port, int c)
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{
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struct nwpserial_port *up;
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up = container_of(port, struct nwpserial_port, port);
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/* check if tx buffer is full */
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wait_for_bits(up, UART_LSR_THRE);
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dcr_write(up->dcr_host, UART_TX, c);
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up->port.icount.tx++;
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}
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static void
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nwpserial_console_write(struct console *co, const char *s, unsigned int count)
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{
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struct nwpserial_port *up = &nwpserial_ports[co->index];
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unsigned long flags;
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int locked = 1;
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if (oops_in_progress)
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locked = spin_trylock_irqsave(&up->port.lock, flags);
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else
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spin_lock_irqsave(&up->port.lock, flags);
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/* save and disable interrupt */
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up->ier = dcr_read(up->dcr_host, UART_IER);
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dcr_write(up->dcr_host, UART_IER, up->ier & ~UART_IER_RDI);
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uart_console_write(&up->port, s, count, nwpserial_console_putchar);
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/* wait for transmitter to become empty */
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while ((dcr_read(up->dcr_host, UART_LSR) & UART_LSR_THRE) == 0)
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cpu_relax();
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/* restore interrupt state */
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dcr_write(up->dcr_host, UART_IER, up->ier);
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if (locked)
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spin_unlock_irqrestore(&up->port.lock, flags);
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}
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static struct uart_driver nwpserial_reg;
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static struct console nwpserial_console = {
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.name = "ttySQ",
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.write = nwpserial_console_write,
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.device = uart_console_device,
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.flags = CON_PRINTBUFFER,
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.index = -1,
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.data = &nwpserial_reg,
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};
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#define NWPSERIAL_CONSOLE (&nwpserial_console)
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#else
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#define NWPSERIAL_CONSOLE NULL
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#endif /* CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL_CONSOLE */
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/**************************************************************************/
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static int nwpserial_request_port(struct uart_port *port)
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{
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return 0;
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}
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static void nwpserial_release_port(struct uart_port *port)
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{
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/* N/A */
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}
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static void nwpserial_config_port(struct uart_port *port, int flags)
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{
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port->type = PORT_NWPSERIAL;
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}
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static irqreturn_t nwpserial_interrupt(int irq, void *dev_id)
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{
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struct nwpserial_port *up = dev_id;
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struct tty_port *port = &up->port.state->port;
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irqreturn_t ret;
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unsigned int iir;
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unsigned char ch;
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spin_lock(&up->port.lock);
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/* check if the uart was the interrupt source. */
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iir = dcr_read(up->dcr_host, UART_IIR);
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if (!iir) {
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ret = IRQ_NONE;
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goto out;
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}
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do {
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up->port.icount.rx++;
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ch = dcr_read(up->dcr_host, UART_RX);
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if (up->port.ignore_status_mask != NWPSERIAL_STATUS_RXVALID)
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tty_insert_flip_char(port, ch, TTY_NORMAL);
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} while (dcr_read(up->dcr_host, UART_LSR) & UART_LSR_DR);
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spin_unlock(&up->port.lock);
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tty_flip_buffer_push(port);
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spin_lock(&up->port.lock);
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ret = IRQ_HANDLED;
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/* clear interrupt */
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dcr_write(up->dcr_host, UART_IIR, 1);
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out:
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spin_unlock(&up->port.lock);
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return ret;
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}
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static int nwpserial_startup(struct uart_port *port)
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{
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struct nwpserial_port *up;
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int err;
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up = container_of(port, struct nwpserial_port, port);
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/* disable flow control by default */
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up->mcr = dcr_read(up->dcr_host, UART_MCR) & ~UART_MCR_AFE;
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dcr_write(up->dcr_host, UART_MCR, up->mcr);
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/* register interrupt handler */
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err = request_irq(up->port.irq, nwpserial_interrupt,
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IRQF_SHARED, "nwpserial", up);
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if (err)
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return err;
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/* enable interrupts */
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up->ier = UART_IER_RDI;
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dcr_write(up->dcr_host, UART_IER, up->ier);
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/* enable receiving */
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up->port.ignore_status_mask &= ~NWPSERIAL_STATUS_RXVALID;
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return 0;
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}
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static void nwpserial_shutdown(struct uart_port *port)
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{
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struct nwpserial_port *up;
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up = container_of(port, struct nwpserial_port, port);
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/* disable receiving */
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up->port.ignore_status_mask |= NWPSERIAL_STATUS_RXVALID;
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/* disable interrupts from this port */
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up->ier = 0;
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dcr_write(up->dcr_host, UART_IER, up->ier);
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/* free irq */
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free_irq(up->port.irq, up);
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}
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static int nwpserial_verify_port(struct uart_port *port,
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struct serial_struct *ser)
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{
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return -EINVAL;
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}
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static const char *nwpserial_type(struct uart_port *port)
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{
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return port->type == PORT_NWPSERIAL ? "nwpserial" : NULL;
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}
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static void nwpserial_set_termios(struct uart_port *port,
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struct ktermios *termios, struct ktermios *old)
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{
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struct nwpserial_port *up;
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up = container_of(port, struct nwpserial_port, port);
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up->port.read_status_mask = NWPSERIAL_STATUS_RXVALID
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| NWPSERIAL_STATUS_TXFULL;
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up->port.ignore_status_mask = 0;
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/* ignore all characters if CREAD is not set */
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if ((termios->c_cflag & CREAD) == 0)
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up->port.ignore_status_mask |= NWPSERIAL_STATUS_RXVALID;
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/* Copy back the old hardware settings */
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if (old)
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tty_termios_copy_hw(termios, old);
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}
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static void nwpserial_break_ctl(struct uart_port *port, int ctl)
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{
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/* N/A */
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}
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static void nwpserial_enable_ms(struct uart_port *port)
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{
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/* N/A */
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}
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static void nwpserial_stop_rx(struct uart_port *port)
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{
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struct nwpserial_port *up;
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up = container_of(port, struct nwpserial_port, port);
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/* don't forward any more data (like !CREAD) */
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up->port.ignore_status_mask = NWPSERIAL_STATUS_RXVALID;
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}
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static void nwpserial_putchar(struct nwpserial_port *up, unsigned char c)
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{
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/* check if tx buffer is full */
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wait_for_bits(up, UART_LSR_THRE);
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dcr_write(up->dcr_host, UART_TX, c);
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up->port.icount.tx++;
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}
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static void nwpserial_start_tx(struct uart_port *port)
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{
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struct nwpserial_port *up;
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struct circ_buf *xmit;
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up = container_of(port, struct nwpserial_port, port);
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xmit = &up->port.state->xmit;
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if (port->x_char) {
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nwpserial_putchar(up, up->port.x_char);
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port->x_char = 0;
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}
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while (!(uart_circ_empty(xmit) || uart_tx_stopped(&up->port))) {
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nwpserial_putchar(up, xmit->buf[xmit->tail]);
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xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE-1);
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}
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}
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static unsigned int nwpserial_get_mctrl(struct uart_port *port)
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{
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return 0;
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}
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static void nwpserial_set_mctrl(struct uart_port *port, unsigned int mctrl)
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{
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/* N/A */
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}
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static void nwpserial_stop_tx(struct uart_port *port)
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{
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/* N/A */
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}
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static unsigned int nwpserial_tx_empty(struct uart_port *port)
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{
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struct nwpserial_port *up;
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unsigned long flags;
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int ret;
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up = container_of(port, struct nwpserial_port, port);
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spin_lock_irqsave(&up->port.lock, flags);
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ret = dcr_read(up->dcr_host, UART_LSR);
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spin_unlock_irqrestore(&up->port.lock, flags);
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return ret & UART_LSR_TEMT ? TIOCSER_TEMT : 0;
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}
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static struct uart_ops nwpserial_pops = {
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.tx_empty = nwpserial_tx_empty,
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.set_mctrl = nwpserial_set_mctrl,
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.get_mctrl = nwpserial_get_mctrl,
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.stop_tx = nwpserial_stop_tx,
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.start_tx = nwpserial_start_tx,
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.stop_rx = nwpserial_stop_rx,
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.enable_ms = nwpserial_enable_ms,
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.break_ctl = nwpserial_break_ctl,
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.startup = nwpserial_startup,
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.shutdown = nwpserial_shutdown,
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.set_termios = nwpserial_set_termios,
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.type = nwpserial_type,
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.release_port = nwpserial_release_port,
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.request_port = nwpserial_request_port,
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.config_port = nwpserial_config_port,
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.verify_port = nwpserial_verify_port,
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};
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static struct uart_driver nwpserial_reg = {
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.owner = THIS_MODULE,
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.driver_name = "nwpserial",
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.dev_name = "ttySQ",
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.major = TTY_MAJOR,
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.minor = 68,
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.nr = NWPSERIAL_NR,
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.cons = NWPSERIAL_CONSOLE,
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};
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int nwpserial_register_port(struct uart_port *port)
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{
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struct nwpserial_port *up = NULL;
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int ret = -1;
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int i;
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static int first = 1;
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int dcr_len;
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int dcr_base;
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struct device_node *dn;
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mutex_lock(&nwpserial_mutex);
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dn = port->dev->of_node;
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if (dn == NULL)
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goto out;
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/* get dcr base. */
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dcr_base = dcr_resource_start(dn, 0);
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/* find matching entry */
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for (i = 0; i < NWPSERIAL_NR; i++)
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if (nwpserial_ports[i].port.iobase == dcr_base) {
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up = &nwpserial_ports[i];
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break;
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}
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/* we didn't find a mtching entry, search for a free port */
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if (up == NULL)
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for (i = 0; i < NWPSERIAL_NR; i++)
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if (nwpserial_ports[i].port.type == PORT_UNKNOWN &&
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nwpserial_ports[i].port.iobase == 0) {
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up = &nwpserial_ports[i];
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break;
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}
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if (up == NULL) {
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ret = -EBUSY;
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goto out;
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}
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if (first)
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uart_register_driver(&nwpserial_reg);
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first = 0;
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up->port.membase = port->membase;
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up->port.irq = port->irq;
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up->port.uartclk = port->uartclk;
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up->port.fifosize = port->fifosize;
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up->port.regshift = port->regshift;
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up->port.iotype = port->iotype;
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up->port.flags = port->flags;
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up->port.mapbase = port->mapbase;
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up->port.private_data = port->private_data;
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if (port->dev)
|
|
up->port.dev = port->dev;
|
|
|
|
if (up->port.iobase != dcr_base) {
|
|
up->port.ops = &nwpserial_pops;
|
|
up->port.fifosize = 16;
|
|
|
|
spin_lock_init(&up->port.lock);
|
|
|
|
up->port.iobase = dcr_base;
|
|
dcr_len = dcr_resource_len(dn, 0);
|
|
|
|
up->dcr_host = dcr_map(dn, dcr_base, dcr_len);
|
|
if (!DCR_MAP_OK(up->dcr_host)) {
|
|
printk(KERN_ERR "Cannot map DCR resources for NWPSERIAL");
|
|
goto out;
|
|
}
|
|
}
|
|
|
|
ret = uart_add_one_port(&nwpserial_reg, &up->port);
|
|
if (ret == 0)
|
|
ret = up->port.line;
|
|
|
|
out:
|
|
mutex_unlock(&nwpserial_mutex);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(nwpserial_register_port);
|
|
|
|
void nwpserial_unregister_port(int line)
|
|
{
|
|
struct nwpserial_port *up = &nwpserial_ports[line];
|
|
mutex_lock(&nwpserial_mutex);
|
|
uart_remove_one_port(&nwpserial_reg, &up->port);
|
|
|
|
up->port.type = PORT_UNKNOWN;
|
|
|
|
mutex_unlock(&nwpserial_mutex);
|
|
}
|
|
EXPORT_SYMBOL(nwpserial_unregister_port);
|
|
|
|
#ifdef CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL_CONSOLE
|
|
static int __init nwpserial_console_init(void)
|
|
{
|
|
struct nwpserial_port *up = NULL;
|
|
struct device_node *dn;
|
|
const char *name;
|
|
int dcr_base;
|
|
int dcr_len;
|
|
int i;
|
|
|
|
/* search for a free port */
|
|
for (i = 0; i < NWPSERIAL_NR; i++)
|
|
if (nwpserial_ports[i].port.type == PORT_UNKNOWN) {
|
|
up = &nwpserial_ports[i];
|
|
break;
|
|
}
|
|
|
|
if (up == NULL)
|
|
return -1;
|
|
|
|
name = of_get_property(of_chosen, "linux,stdout-path", NULL);
|
|
if (name == NULL)
|
|
return -1;
|
|
|
|
dn = of_find_node_by_path(name);
|
|
if (!dn)
|
|
return -1;
|
|
|
|
spin_lock_init(&up->port.lock);
|
|
up->port.ops = &nwpserial_pops;
|
|
up->port.type = PORT_NWPSERIAL;
|
|
up->port.fifosize = 16;
|
|
|
|
dcr_base = dcr_resource_start(dn, 0);
|
|
dcr_len = dcr_resource_len(dn, 0);
|
|
up->port.iobase = dcr_base;
|
|
|
|
up->dcr_host = dcr_map(dn, dcr_base, dcr_len);
|
|
if (!DCR_MAP_OK(up->dcr_host)) {
|
|
printk("Cannot map DCR resources for SERIAL");
|
|
return -1;
|
|
}
|
|
register_console(&nwpserial_console);
|
|
return 0;
|
|
}
|
|
console_initcall(nwpserial_console_init);
|
|
#endif /* CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL_CONSOLE */
|