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linux/drivers/tty/serial/mcf.c
Johan Hovold 5d148754da serial: mcf: drop low-latency workaround 
Commit 5275ad70fe ("tty: serial: mcf: drop uart_port->lock before
calling tty_flip_buffer_push()") claimed to address a locking
issue but only provided a dubious lockdep splat from an unrelated
driver, which in the end turned out to be due a broken local change
carried by the author.

Unfortunately these patches were merged before the issue had been
analysed properly so the commit messages makes no sense whatsoever.

The real issue was first seen on RT which at the time effectively always
set the low_latency flag for all serial drivers by patching
tty_flip_buffer_push(). This in turn revealed that many drivers did not
handle the infamous low_latency behaviour which meant that data was
pushed immediately to the line discipline instead of being deferred to a
work queue.

Since commit a9c3f68f3c ("tty: Fix low_latency BUG"),
tty_flip_buffer_push() always schedules a work item to push data to the
line discipline and there's no need to keep any low_latency hacks
around.

Link: https://lore.kernel.org/linux-serial/cover.1376923198.git.viresh.kumar@linaro.org/
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210421095509.3024-14-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-04-22 12:09:25 +02:00

705 lines
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// SPDX-License-Identifier: GPL-2.0+
/****************************************************************************/
/*
* mcf.c -- Freescale ColdFire UART driver
*
* (C) Copyright 2003-2007, Greg Ungerer <gerg@uclinux.org>
*/
/****************************************************************************/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/console.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial.h>
#include <linux/serial_core.h>
#include <linux/io.h>
#include <linux/uaccess.h>
#include <linux/platform_device.h>
#include <asm/coldfire.h>
#include <asm/mcfsim.h>
#include <asm/mcfuart.h>
#include <asm/nettel.h>
/****************************************************************************/
/*
* Some boards implement the DTR/DCD lines using GPIO lines, most
* don't. Dummy out the access macros for those that don't. Those
* that do should define these macros somewhere in there board
* specific inlude files.
*/
#if !defined(mcf_getppdcd)
#define mcf_getppdcd(p) (1)
#endif
#if !defined(mcf_getppdtr)
#define mcf_getppdtr(p) (1)
#endif
#if !defined(mcf_setppdtr)
#define mcf_setppdtr(p, v) do { } while (0)
#endif
/****************************************************************************/
/*
* Local per-uart structure.
*/
struct mcf_uart {
struct uart_port port;
unsigned int sigs; /* Local copy of line sigs */
unsigned char imr; /* Local IMR mirror */
};
/****************************************************************************/
static unsigned int mcf_tx_empty(struct uart_port *port)
{
return (readb(port->membase + MCFUART_USR) & MCFUART_USR_TXEMPTY) ?
TIOCSER_TEMT : 0;
}
/****************************************************************************/
static unsigned int mcf_get_mctrl(struct uart_port *port)
{
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
unsigned int sigs;
sigs = (readb(port->membase + MCFUART_UIPR) & MCFUART_UIPR_CTS) ?
0 : TIOCM_CTS;
sigs |= (pp->sigs & TIOCM_RTS);
sigs |= (mcf_getppdcd(port->line) ? TIOCM_CD : 0);
sigs |= (mcf_getppdtr(port->line) ? TIOCM_DTR : 0);
return sigs;
}
/****************************************************************************/
static void mcf_set_mctrl(struct uart_port *port, unsigned int sigs)
{
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
pp->sigs = sigs;
mcf_setppdtr(port->line, (sigs & TIOCM_DTR));
if (sigs & TIOCM_RTS)
writeb(MCFUART_UOP_RTS, port->membase + MCFUART_UOP1);
else
writeb(MCFUART_UOP_RTS, port->membase + MCFUART_UOP0);
}
/****************************************************************************/
static void mcf_start_tx(struct uart_port *port)
{
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
if (port->rs485.flags & SER_RS485_ENABLED) {
/* Enable Transmitter */
writeb(MCFUART_UCR_TXENABLE, port->membase + MCFUART_UCR);
/* Manually assert RTS */
writeb(MCFUART_UOP_RTS, port->membase + MCFUART_UOP1);
}
pp->imr |= MCFUART_UIR_TXREADY;
writeb(pp->imr, port->membase + MCFUART_UIMR);
}
/****************************************************************************/
static void mcf_stop_tx(struct uart_port *port)
{
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
pp->imr &= ~MCFUART_UIR_TXREADY;
writeb(pp->imr, port->membase + MCFUART_UIMR);
}
/****************************************************************************/
static void mcf_stop_rx(struct uart_port *port)
{
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
pp->imr &= ~MCFUART_UIR_RXREADY;
writeb(pp->imr, port->membase + MCFUART_UIMR);
}
/****************************************************************************/
static void mcf_break_ctl(struct uart_port *port, int break_state)
{
unsigned long flags;
spin_lock_irqsave(&port->lock, flags);
if (break_state == -1)
writeb(MCFUART_UCR_CMDBREAKSTART, port->membase + MCFUART_UCR);
else
writeb(MCFUART_UCR_CMDBREAKSTOP, port->membase + MCFUART_UCR);
spin_unlock_irqrestore(&port->lock, flags);
}
/****************************************************************************/
static int mcf_startup(struct uart_port *port)
{
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
unsigned long flags;
spin_lock_irqsave(&port->lock, flags);
/* Reset UART, get it into known state... */
writeb(MCFUART_UCR_CMDRESETRX, port->membase + MCFUART_UCR);
writeb(MCFUART_UCR_CMDRESETTX, port->membase + MCFUART_UCR);
/* Enable the UART transmitter and receiver */
writeb(MCFUART_UCR_RXENABLE | MCFUART_UCR_TXENABLE,
port->membase + MCFUART_UCR);
/* Enable RX interrupts now */
pp->imr = MCFUART_UIR_RXREADY;
writeb(pp->imr, port->membase + MCFUART_UIMR);
spin_unlock_irqrestore(&port->lock, flags);
return 0;
}
/****************************************************************************/
static void mcf_shutdown(struct uart_port *port)
{
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
unsigned long flags;
spin_lock_irqsave(&port->lock, flags);
/* Disable all interrupts now */
pp->imr = 0;
writeb(pp->imr, port->membase + MCFUART_UIMR);
/* Disable UART transmitter and receiver */
writeb(MCFUART_UCR_CMDRESETRX, port->membase + MCFUART_UCR);
writeb(MCFUART_UCR_CMDRESETTX, port->membase + MCFUART_UCR);
spin_unlock_irqrestore(&port->lock, flags);
}
/****************************************************************************/
static void mcf_set_termios(struct uart_port *port, struct ktermios *termios,
struct ktermios *old)
{
unsigned long flags;
unsigned int baud, baudclk;
#if defined(CONFIG_M5272)
unsigned int baudfr;
#endif
unsigned char mr1, mr2;
baud = uart_get_baud_rate(port, termios, old, 0, 230400);
#if defined(CONFIG_M5272)
baudclk = (MCF_BUSCLK / baud) / 32;
baudfr = (((MCF_BUSCLK / baud) + 1) / 2) % 16;
#else
baudclk = ((MCF_BUSCLK / baud) + 16) / 32;
#endif
mr1 = MCFUART_MR1_RXIRQRDY | MCFUART_MR1_RXERRCHAR;
mr2 = 0;
switch (termios->c_cflag & CSIZE) {
case CS5: mr1 |= MCFUART_MR1_CS5; break;
case CS6: mr1 |= MCFUART_MR1_CS6; break;
case CS7: mr1 |= MCFUART_MR1_CS7; break;
case CS8:
default: mr1 |= MCFUART_MR1_CS8; break;
}
if (termios->c_cflag & PARENB) {
if (termios->c_cflag & CMSPAR) {
if (termios->c_cflag & PARODD)
mr1 |= MCFUART_MR1_PARITYMARK;
else
mr1 |= MCFUART_MR1_PARITYSPACE;
} else {
if (termios->c_cflag & PARODD)
mr1 |= MCFUART_MR1_PARITYODD;
else
mr1 |= MCFUART_MR1_PARITYEVEN;
}
} else {
mr1 |= MCFUART_MR1_PARITYNONE;
}
/*
* FIXME: port->read_status_mask and port->ignore_status_mask
* need to be initialized based on termios settings for
* INPCK, IGNBRK, IGNPAR, PARMRK, BRKINT
*/
if (termios->c_cflag & CSTOPB)
mr2 |= MCFUART_MR2_STOP2;
else
mr2 |= MCFUART_MR2_STOP1;
if (termios->c_cflag & CRTSCTS) {
mr1 |= MCFUART_MR1_RXRTS;
mr2 |= MCFUART_MR2_TXCTS;
}
spin_lock_irqsave(&port->lock, flags);
if (port->rs485.flags & SER_RS485_ENABLED) {
dev_dbg(port->dev, "Setting UART to RS485\n");
mr2 |= MCFUART_MR2_TXRTS;
}
uart_update_timeout(port, termios->c_cflag, baud);
writeb(MCFUART_UCR_CMDRESETRX, port->membase + MCFUART_UCR);
writeb(MCFUART_UCR_CMDRESETTX, port->membase + MCFUART_UCR);
writeb(MCFUART_UCR_CMDRESETMRPTR, port->membase + MCFUART_UCR);
writeb(mr1, port->membase + MCFUART_UMR);
writeb(mr2, port->membase + MCFUART_UMR);
writeb((baudclk & 0xff00) >> 8, port->membase + MCFUART_UBG1);
writeb((baudclk & 0xff), port->membase + MCFUART_UBG2);
#if defined(CONFIG_M5272)
writeb((baudfr & 0x0f), port->membase + MCFUART_UFPD);
#endif
writeb(MCFUART_UCSR_RXCLKTIMER | MCFUART_UCSR_TXCLKTIMER,
port->membase + MCFUART_UCSR);
writeb(MCFUART_UCR_RXENABLE | MCFUART_UCR_TXENABLE,
port->membase + MCFUART_UCR);
spin_unlock_irqrestore(&port->lock, flags);
}
/****************************************************************************/
static void mcf_rx_chars(struct mcf_uart *pp)
{
struct uart_port *port = &pp->port;
unsigned char status, ch, flag;
while ((status = readb(port->membase + MCFUART_USR)) & MCFUART_USR_RXREADY) {
ch = readb(port->membase + MCFUART_URB);
flag = TTY_NORMAL;
port->icount.rx++;
if (status & MCFUART_USR_RXERR) {
writeb(MCFUART_UCR_CMDRESETERR,
port->membase + MCFUART_UCR);
if (status & MCFUART_USR_RXBREAK) {
port->icount.brk++;
if (uart_handle_break(port))
continue;
} else if (status & MCFUART_USR_RXPARITY) {
port->icount.parity++;
} else if (status & MCFUART_USR_RXOVERRUN) {
port->icount.overrun++;
} else if (status & MCFUART_USR_RXFRAMING) {
port->icount.frame++;
}
status &= port->read_status_mask;
if (status & MCFUART_USR_RXBREAK)
flag = TTY_BREAK;
else if (status & MCFUART_USR_RXPARITY)
flag = TTY_PARITY;
else if (status & MCFUART_USR_RXFRAMING)
flag = TTY_FRAME;
}
if (uart_handle_sysrq_char(port, ch))
continue;
uart_insert_char(port, status, MCFUART_USR_RXOVERRUN, ch, flag);
}
tty_flip_buffer_push(&port->state->port);
}
/****************************************************************************/
static void mcf_tx_chars(struct mcf_uart *pp)
{
struct uart_port *port = &pp->port;
struct circ_buf *xmit = &port->state->xmit;
if (port->x_char) {
/* Send special char - probably flow control */
writeb(port->x_char, port->membase + MCFUART_UTB);
port->x_char = 0;
port->icount.tx++;
return;
}
while (readb(port->membase + MCFUART_USR) & MCFUART_USR_TXREADY) {
if (xmit->head == xmit->tail)
break;
writeb(xmit->buf[xmit->tail], port->membase + MCFUART_UTB);
xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE -1);
port->icount.tx++;
}
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(port);
if (xmit->head == xmit->tail) {
pp->imr &= ~MCFUART_UIR_TXREADY;
writeb(pp->imr, port->membase + MCFUART_UIMR);
/* Disable TX to negate RTS automatically */
if (port->rs485.flags & SER_RS485_ENABLED)
writeb(MCFUART_UCR_TXDISABLE,
port->membase + MCFUART_UCR);
}
}
/****************************************************************************/
static irqreturn_t mcf_interrupt(int irq, void *data)
{
struct uart_port *port = data;
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
unsigned int isr;
irqreturn_t ret = IRQ_NONE;
isr = readb(port->membase + MCFUART_UISR) & pp->imr;
spin_lock(&port->lock);
if (isr & MCFUART_UIR_RXREADY) {
mcf_rx_chars(pp);
ret = IRQ_HANDLED;
}
if (isr & MCFUART_UIR_TXREADY) {
mcf_tx_chars(pp);
ret = IRQ_HANDLED;
}
spin_unlock(&port->lock);
return ret;
}
/****************************************************************************/
static void mcf_config_port(struct uart_port *port, int flags)
{
port->type = PORT_MCF;
port->fifosize = MCFUART_TXFIFOSIZE;
/* Clear mask, so no surprise interrupts. */
writeb(0, port->membase + MCFUART_UIMR);
if (request_irq(port->irq, mcf_interrupt, 0, "UART", port))
printk(KERN_ERR "MCF: unable to attach ColdFire UART %d "
"interrupt vector=%d\n", port->line, port->irq);
}
/****************************************************************************/
static const char *mcf_type(struct uart_port *port)
{
return (port->type == PORT_MCF) ? "ColdFire UART" : NULL;
}
/****************************************************************************/
static int mcf_request_port(struct uart_port *port)
{
/* UARTs always present */
return 0;
}
/****************************************************************************/
static void mcf_release_port(struct uart_port *port)
{
/* Nothing to release... */
}
/****************************************************************************/
static int mcf_verify_port(struct uart_port *port, struct serial_struct *ser)
{
if ((ser->type != PORT_UNKNOWN) && (ser->type != PORT_MCF))
return -EINVAL;
return 0;
}
/****************************************************************************/
/* Enable or disable the RS485 support */
static int mcf_config_rs485(struct uart_port *port, struct serial_rs485 *rs485)
{
unsigned char mr1, mr2;
/* Get mode registers */
mr1 = readb(port->membase + MCFUART_UMR);
mr2 = readb(port->membase + MCFUART_UMR);
if (rs485->flags & SER_RS485_ENABLED) {
dev_dbg(port->dev, "Setting UART to RS485\n");
/* Automatically negate RTS after TX completes */
mr2 |= MCFUART_MR2_TXRTS;
} else {
dev_dbg(port->dev, "Setting UART to RS232\n");
mr2 &= ~MCFUART_MR2_TXRTS;
}
writeb(mr1, port->membase + MCFUART_UMR);
writeb(mr2, port->membase + MCFUART_UMR);
port->rs485 = *rs485;
return 0;
}
/****************************************************************************/
/*
* Define the basic serial functions we support.
*/
static const struct uart_ops mcf_uart_ops = {
.tx_empty = mcf_tx_empty,
.get_mctrl = mcf_get_mctrl,
.set_mctrl = mcf_set_mctrl,
.start_tx = mcf_start_tx,
.stop_tx = mcf_stop_tx,
.stop_rx = mcf_stop_rx,
.break_ctl = mcf_break_ctl,
.startup = mcf_startup,
.shutdown = mcf_shutdown,
.set_termios = mcf_set_termios,
.type = mcf_type,
.request_port = mcf_request_port,
.release_port = mcf_release_port,
.config_port = mcf_config_port,
.verify_port = mcf_verify_port,
};
static struct mcf_uart mcf_ports[4];
#define MCF_MAXPORTS ARRAY_SIZE(mcf_ports)
/****************************************************************************/
#if defined(CONFIG_SERIAL_MCF_CONSOLE)
/****************************************************************************/
int __init early_mcf_setup(struct mcf_platform_uart *platp)
{
struct uart_port *port;
int i;
for (i = 0; ((i < MCF_MAXPORTS) && (platp[i].mapbase)); i++) {
port = &mcf_ports[i].port;
port->line = i;
port->type = PORT_MCF;
port->mapbase = platp[i].mapbase;
port->membase = (platp[i].membase) ? platp[i].membase :
(unsigned char __iomem *) port->mapbase;
port->iotype = SERIAL_IO_MEM;
port->irq = platp[i].irq;
port->uartclk = MCF_BUSCLK;
port->flags = UPF_BOOT_AUTOCONF;
port->rs485_config = mcf_config_rs485;
port->ops = &mcf_uart_ops;
}
return 0;
}
/****************************************************************************/
static void mcf_console_putc(struct console *co, const char c)
{
struct uart_port *port = &(mcf_ports + co->index)->port;
int i;
for (i = 0; (i < 0x10000); i++) {
if (readb(port->membase + MCFUART_USR) & MCFUART_USR_TXREADY)
break;
}
writeb(c, port->membase + MCFUART_UTB);
for (i = 0; (i < 0x10000); i++) {
if (readb(port->membase + MCFUART_USR) & MCFUART_USR_TXREADY)
break;
}
}
/****************************************************************************/
static void mcf_console_write(struct console *co, const char *s, unsigned int count)
{
for (; (count); count--, s++) {
mcf_console_putc(co, *s);
if (*s == '\n')
mcf_console_putc(co, '\r');
}
}
/****************************************************************************/
static int __init mcf_console_setup(struct console *co, char *options)
{
struct uart_port *port;
int baud = CONFIG_SERIAL_MCF_BAUDRATE;
int bits = 8;
int parity = 'n';
int flow = 'n';
if ((co->index < 0) || (co->index >= MCF_MAXPORTS))
co->index = 0;
port = &mcf_ports[co->index].port;
if (port->membase == 0)
return -ENODEV;
if (options)
uart_parse_options(options, &baud, &parity, &bits, &flow);
return uart_set_options(port, co, baud, parity, bits, flow);
}
/****************************************************************************/
static struct uart_driver mcf_driver;
static struct console mcf_console = {
.name = "ttyS",
.write = mcf_console_write,
.device = uart_console_device,
.setup = mcf_console_setup,
.flags = CON_PRINTBUFFER,
.index = -1,
.data = &mcf_driver,
};
static int __init mcf_console_init(void)
{
register_console(&mcf_console);
return 0;
}
console_initcall(mcf_console_init);
#define MCF_CONSOLE &mcf_console
/****************************************************************************/
#else
/****************************************************************************/
#define MCF_CONSOLE NULL
/****************************************************************************/
#endif /* CONFIG_SERIAL_MCF_CONSOLE */
/****************************************************************************/
/*
* Define the mcf UART driver structure.
*/
static struct uart_driver mcf_driver = {
.owner = THIS_MODULE,
.driver_name = "mcf",
.dev_name = "ttyS",
.major = TTY_MAJOR,
.minor = 64,
.nr = MCF_MAXPORTS,
.cons = MCF_CONSOLE,
};
/****************************************************************************/
static int mcf_probe(struct platform_device *pdev)
{
struct mcf_platform_uart *platp = dev_get_platdata(&pdev->dev);
struct uart_port *port;
int i;
for (i = 0; ((i < MCF_MAXPORTS) && (platp[i].mapbase)); i++) {
port = &mcf_ports[i].port;
port->line = i;
port->type = PORT_MCF;
port->mapbase = platp[i].mapbase;
port->membase = (platp[i].membase) ? platp[i].membase :
(unsigned char __iomem *) platp[i].mapbase;
port->dev = &pdev->dev;
port->iotype = SERIAL_IO_MEM;
port->irq = platp[i].irq;
port->uartclk = MCF_BUSCLK;
port->ops = &mcf_uart_ops;
port->flags = UPF_BOOT_AUTOCONF;
port->rs485_config = mcf_config_rs485;
port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_MCF_CONSOLE);
uart_add_one_port(&mcf_driver, port);
}
return 0;
}
/****************************************************************************/
static int mcf_remove(struct platform_device *pdev)
{
struct uart_port *port;
int i;
for (i = 0; (i < MCF_MAXPORTS); i++) {
port = &mcf_ports[i].port;
if (port)
uart_remove_one_port(&mcf_driver, port);
}
return 0;
}
/****************************************************************************/
static struct platform_driver mcf_platform_driver = {
.probe = mcf_probe,
.remove = mcf_remove,
.driver = {
.name = "mcfuart",
},
};
/****************************************************************************/
static int __init mcf_init(void)
{
int rc;
printk("ColdFire internal UART serial driver\n");
rc = uart_register_driver(&mcf_driver);
if (rc)
return rc;
rc = platform_driver_register(&mcf_platform_driver);
if (rc) {
uart_unregister_driver(&mcf_driver);
return rc;
}
return 0;
}
/****************************************************************************/
static void __exit mcf_exit(void)
{
platform_driver_unregister(&mcf_platform_driver);
uart_unregister_driver(&mcf_driver);
}
/****************************************************************************/
module_init(mcf_init);
module_exit(mcf_exit);
MODULE_AUTHOR("Greg Ungerer <gerg@uclinux.org>");
MODULE_DESCRIPTION("Freescale ColdFire UART driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:mcfuart");
/****************************************************************************/
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