linux-stable/drivers/tty/serial/8250/8250_dw.c

648 lines
16 KiB
C
Raw Normal View History

/*
* Synopsys DesignWare 8250 driver.
*
* Copyright 2011 Picochip, Jamie Iles.
* Copyright 2013 Intel Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* The Synopsys DesignWare 8250 has an extra feature whereby it detects if the
* LCR is written whilst busy. If it is, then a busy detect interrupt is
* raised, the LCR needs to be rewritten and the uart status register read.
*/
#include <linux/device.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/serial_8250.h>
#include <linux/serial_reg.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/acpi.h>
#include <linux/clk.h>
#include <linux/reset.h>
#include <linux/pm_runtime.h>
#include <asm/byteorder.h>
#include "8250.h"
/* Offsets for the DesignWare specific registers */
#define DW_UART_USR 0x1f /* UART Status Register */
#define DW_UART_CPR 0xf4 /* Component Parameter Register */
#define DW_UART_UCV 0xf8 /* UART Component Version */
/* Component Parameter Register bits */
#define DW_UART_CPR_ABP_DATA_WIDTH (3 << 0)
#define DW_UART_CPR_AFCE_MODE (1 << 4)
#define DW_UART_CPR_THRE_MODE (1 << 5)
#define DW_UART_CPR_SIR_MODE (1 << 6)
#define DW_UART_CPR_SIR_LP_MODE (1 << 7)
#define DW_UART_CPR_ADDITIONAL_FEATURES (1 << 8)
#define DW_UART_CPR_FIFO_ACCESS (1 << 9)
#define DW_UART_CPR_FIFO_STAT (1 << 10)
#define DW_UART_CPR_SHADOW (1 << 11)
#define DW_UART_CPR_ENCODED_PARMS (1 << 12)
#define DW_UART_CPR_DMA_EXTRA (1 << 13)
#define DW_UART_CPR_FIFO_MODE (0xff << 16)
/* Helper for fifo size calculation */
#define DW_UART_CPR_FIFO_SIZE(a) (((a >> 16) & 0xff) * 16)
struct dw8250_data {
u8 usr_reg;
int line;
int msr_mask_on;
int msr_mask_off;
struct clk *clk;
struct clk *pclk;
struct reset_control *rst;
struct uart_8250_dma dma;
};
#define BYT_PRV_CLK 0x800
#define BYT_PRV_CLK_EN (1 << 0)
#define BYT_PRV_CLK_M_VAL_SHIFT 1
#define BYT_PRV_CLK_N_VAL_SHIFT 16
#define BYT_PRV_CLK_UPDATE (1 << 31)
static inline int dw8250_modify_msr(struct uart_port *p, int offset, int value)
{
struct dw8250_data *d = p->private_data;
/* Override any modem control signals if needed */
if (offset == UART_MSR) {
value |= d->msr_mask_on;
value &= ~d->msr_mask_off;
}
return value;
}
serial: 8250_dw: Improve unwritable LCR workaround When configured with UART_16550_COMPATIBLE=NO or in versions prior to the introduction of this option, the Designware UART will ignore writes to the LCR if the UART is busy. The current workaround saves a copy of the last written LCR and re-writes it in the ISR for a special interrupt that is raised when a write was ignored. Unfortunately, interrupts are typically disabled prior to performing a sequence of register writes that include the LCR so the point at which the retry occurs is too late. An example is serial8250_do_set_termios() where an ignored LCR write results in the baud divisor not being set and instead a garbage character is sent out the transmitter. Furthermore, since serial_port_out() offers no way to indicate failure, a serious effort must be made to ensure that the LCR is actually updated before returning back to the caller. This is difficult, however, as a UART that was busy during the first attempt is likely to still be busy when a subsequent attempt is made unless some extra action is taken. This updated workaround reads back the LCR after each write to confirm that the new value was accepted by the hardware. Should the hardware ignore a write, the TX/RX FIFOs are cleared and the receive buffer read before attempting to rewrite the LCR out of the hope that doing so will force the UART into an idle state. While this may seem unnecessarily aggressive, writes to the LCR are used to change the baud rate, parity, stop bit, or data length so the data that may be lost is likely not important. Admittedly, this is far from ideal but it seems to be the best that can be done given the hardware limitations. Lastly, the revised workaround doesn't touch the LCR in the ISR, so it avoids the possibility of a "serial8250: too much work for irq" lock up. This problem is rare in real situations but can be reproduced easily by wiring up two UARTs and running the following commands. # stty -F /dev/ttyS1 echo # stty -F /dev/ttyS2 echo # cat /dev/ttyS1 & [1] 375 # echo asdf > /dev/ttyS1 asdf [ 27.700000] serial8250: too much work for irq96 [ 27.700000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.740000] serial8250: too much work for irq96 Signed-off-by: Tim Kryger <tim.kryger@linaro.org> Reviewed-by: Matt Porter <matt.porter@linaro.org> Reviewed-by: Markus Mayer <markus.mayer@linaro.org> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-10-01 17:18:08 +00:00
static void dw8250_force_idle(struct uart_port *p)
{
struct uart_8250_port *up = up_to_u8250p(p);
serial8250_clear_and_reinit_fifos(up);
serial: 8250_dw: Improve unwritable LCR workaround When configured with UART_16550_COMPATIBLE=NO or in versions prior to the introduction of this option, the Designware UART will ignore writes to the LCR if the UART is busy. The current workaround saves a copy of the last written LCR and re-writes it in the ISR for a special interrupt that is raised when a write was ignored. Unfortunately, interrupts are typically disabled prior to performing a sequence of register writes that include the LCR so the point at which the retry occurs is too late. An example is serial8250_do_set_termios() where an ignored LCR write results in the baud divisor not being set and instead a garbage character is sent out the transmitter. Furthermore, since serial_port_out() offers no way to indicate failure, a serious effort must be made to ensure that the LCR is actually updated before returning back to the caller. This is difficult, however, as a UART that was busy during the first attempt is likely to still be busy when a subsequent attempt is made unless some extra action is taken. This updated workaround reads back the LCR after each write to confirm that the new value was accepted by the hardware. Should the hardware ignore a write, the TX/RX FIFOs are cleared and the receive buffer read before attempting to rewrite the LCR out of the hope that doing so will force the UART into an idle state. While this may seem unnecessarily aggressive, writes to the LCR are used to change the baud rate, parity, stop bit, or data length so the data that may be lost is likely not important. Admittedly, this is far from ideal but it seems to be the best that can be done given the hardware limitations. Lastly, the revised workaround doesn't touch the LCR in the ISR, so it avoids the possibility of a "serial8250: too much work for irq" lock up. This problem is rare in real situations but can be reproduced easily by wiring up two UARTs and running the following commands. # stty -F /dev/ttyS1 echo # stty -F /dev/ttyS2 echo # cat /dev/ttyS1 & [1] 375 # echo asdf > /dev/ttyS1 asdf [ 27.700000] serial8250: too much work for irq96 [ 27.700000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.740000] serial8250: too much work for irq96 Signed-off-by: Tim Kryger <tim.kryger@linaro.org> Reviewed-by: Matt Porter <matt.porter@linaro.org> Reviewed-by: Markus Mayer <markus.mayer@linaro.org> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-10-01 17:18:08 +00:00
(void)p->serial_in(p, UART_RX);
}
static void dw8250_serial_out(struct uart_port *p, int offset, int value)
{
writeb(value, p->membase + (offset << p->regshift));
serial: 8250_dw: Improve unwritable LCR workaround When configured with UART_16550_COMPATIBLE=NO or in versions prior to the introduction of this option, the Designware UART will ignore writes to the LCR if the UART is busy. The current workaround saves a copy of the last written LCR and re-writes it in the ISR for a special interrupt that is raised when a write was ignored. Unfortunately, interrupts are typically disabled prior to performing a sequence of register writes that include the LCR so the point at which the retry occurs is too late. An example is serial8250_do_set_termios() where an ignored LCR write results in the baud divisor not being set and instead a garbage character is sent out the transmitter. Furthermore, since serial_port_out() offers no way to indicate failure, a serious effort must be made to ensure that the LCR is actually updated before returning back to the caller. This is difficult, however, as a UART that was busy during the first attempt is likely to still be busy when a subsequent attempt is made unless some extra action is taken. This updated workaround reads back the LCR after each write to confirm that the new value was accepted by the hardware. Should the hardware ignore a write, the TX/RX FIFOs are cleared and the receive buffer read before attempting to rewrite the LCR out of the hope that doing so will force the UART into an idle state. While this may seem unnecessarily aggressive, writes to the LCR are used to change the baud rate, parity, stop bit, or data length so the data that may be lost is likely not important. Admittedly, this is far from ideal but it seems to be the best that can be done given the hardware limitations. Lastly, the revised workaround doesn't touch the LCR in the ISR, so it avoids the possibility of a "serial8250: too much work for irq" lock up. This problem is rare in real situations but can be reproduced easily by wiring up two UARTs and running the following commands. # stty -F /dev/ttyS1 echo # stty -F /dev/ttyS2 echo # cat /dev/ttyS1 & [1] 375 # echo asdf > /dev/ttyS1 asdf [ 27.700000] serial8250: too much work for irq96 [ 27.700000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.740000] serial8250: too much work for irq96 Signed-off-by: Tim Kryger <tim.kryger@linaro.org> Reviewed-by: Matt Porter <matt.porter@linaro.org> Reviewed-by: Markus Mayer <markus.mayer@linaro.org> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-10-01 17:18:08 +00:00
/* Make sure LCR write wasn't ignored */
if (offset == UART_LCR) {
int tries = 1000;
while (tries--) {
unsigned int lcr = p->serial_in(p, UART_LCR);
if ((value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR))
serial: 8250_dw: Improve unwritable LCR workaround When configured with UART_16550_COMPATIBLE=NO or in versions prior to the introduction of this option, the Designware UART will ignore writes to the LCR if the UART is busy. The current workaround saves a copy of the last written LCR and re-writes it in the ISR for a special interrupt that is raised when a write was ignored. Unfortunately, interrupts are typically disabled prior to performing a sequence of register writes that include the LCR so the point at which the retry occurs is too late. An example is serial8250_do_set_termios() where an ignored LCR write results in the baud divisor not being set and instead a garbage character is sent out the transmitter. Furthermore, since serial_port_out() offers no way to indicate failure, a serious effort must be made to ensure that the LCR is actually updated before returning back to the caller. This is difficult, however, as a UART that was busy during the first attempt is likely to still be busy when a subsequent attempt is made unless some extra action is taken. This updated workaround reads back the LCR after each write to confirm that the new value was accepted by the hardware. Should the hardware ignore a write, the TX/RX FIFOs are cleared and the receive buffer read before attempting to rewrite the LCR out of the hope that doing so will force the UART into an idle state. While this may seem unnecessarily aggressive, writes to the LCR are used to change the baud rate, parity, stop bit, or data length so the data that may be lost is likely not important. Admittedly, this is far from ideal but it seems to be the best that can be done given the hardware limitations. Lastly, the revised workaround doesn't touch the LCR in the ISR, so it avoids the possibility of a "serial8250: too much work for irq" lock up. This problem is rare in real situations but can be reproduced easily by wiring up two UARTs and running the following commands. # stty -F /dev/ttyS1 echo # stty -F /dev/ttyS2 echo # cat /dev/ttyS1 & [1] 375 # echo asdf > /dev/ttyS1 asdf [ 27.700000] serial8250: too much work for irq96 [ 27.700000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.740000] serial8250: too much work for irq96 Signed-off-by: Tim Kryger <tim.kryger@linaro.org> Reviewed-by: Matt Porter <matt.porter@linaro.org> Reviewed-by: Markus Mayer <markus.mayer@linaro.org> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-10-01 17:18:08 +00:00
return;
dw8250_force_idle(p);
writeb(value, p->membase + (UART_LCR << p->regshift));
}
/*
* FIXME: this deadlocks if port->lock is already held
* dev_err(p->dev, "Couldn't set LCR to %d\n", value);
*/
serial: 8250_dw: Improve unwritable LCR workaround When configured with UART_16550_COMPATIBLE=NO or in versions prior to the introduction of this option, the Designware UART will ignore writes to the LCR if the UART is busy. The current workaround saves a copy of the last written LCR and re-writes it in the ISR for a special interrupt that is raised when a write was ignored. Unfortunately, interrupts are typically disabled prior to performing a sequence of register writes that include the LCR so the point at which the retry occurs is too late. An example is serial8250_do_set_termios() where an ignored LCR write results in the baud divisor not being set and instead a garbage character is sent out the transmitter. Furthermore, since serial_port_out() offers no way to indicate failure, a serious effort must be made to ensure that the LCR is actually updated before returning back to the caller. This is difficult, however, as a UART that was busy during the first attempt is likely to still be busy when a subsequent attempt is made unless some extra action is taken. This updated workaround reads back the LCR after each write to confirm that the new value was accepted by the hardware. Should the hardware ignore a write, the TX/RX FIFOs are cleared and the receive buffer read before attempting to rewrite the LCR out of the hope that doing so will force the UART into an idle state. While this may seem unnecessarily aggressive, writes to the LCR are used to change the baud rate, parity, stop bit, or data length so the data that may be lost is likely not important. Admittedly, this is far from ideal but it seems to be the best that can be done given the hardware limitations. Lastly, the revised workaround doesn't touch the LCR in the ISR, so it avoids the possibility of a "serial8250: too much work for irq" lock up. This problem is rare in real situations but can be reproduced easily by wiring up two UARTs and running the following commands. # stty -F /dev/ttyS1 echo # stty -F /dev/ttyS2 echo # cat /dev/ttyS1 & [1] 375 # echo asdf > /dev/ttyS1 asdf [ 27.700000] serial8250: too much work for irq96 [ 27.700000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.740000] serial8250: too much work for irq96 Signed-off-by: Tim Kryger <tim.kryger@linaro.org> Reviewed-by: Matt Porter <matt.porter@linaro.org> Reviewed-by: Markus Mayer <markus.mayer@linaro.org> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-10-01 17:18:08 +00:00
}
}
static unsigned int dw8250_serial_in(struct uart_port *p, int offset)
{
unsigned int value = readb(p->membase + (offset << p->regshift));
return dw8250_modify_msr(p, offset, value);
}
#ifdef CONFIG_64BIT
static unsigned int dw8250_serial_inq(struct uart_port *p, int offset)
{
unsigned int value;
value = (u8)__raw_readq(p->membase + (offset << p->regshift));
return dw8250_modify_msr(p, offset, value);
}
static void dw8250_serial_outq(struct uart_port *p, int offset, int value)
{
value &= 0xff;
__raw_writeq(value, p->membase + (offset << p->regshift));
/* Read back to ensure register write ordering. */
__raw_readq(p->membase + (UART_LCR << p->regshift));
/* Make sure LCR write wasn't ignored */
if (offset == UART_LCR) {
int tries = 1000;
while (tries--) {
unsigned int lcr = p->serial_in(p, UART_LCR);
if ((value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR))
return;
dw8250_force_idle(p);
__raw_writeq(value & 0xff,
p->membase + (UART_LCR << p->regshift));
}
/*
* FIXME: this deadlocks if port->lock is already held
* dev_err(p->dev, "Couldn't set LCR to %d\n", value);
*/
}
}
#endif /* CONFIG_64BIT */
static void dw8250_serial_out32(struct uart_port *p, int offset, int value)
{
writel(value, p->membase + (offset << p->regshift));
serial: 8250_dw: Improve unwritable LCR workaround When configured with UART_16550_COMPATIBLE=NO or in versions prior to the introduction of this option, the Designware UART will ignore writes to the LCR if the UART is busy. The current workaround saves a copy of the last written LCR and re-writes it in the ISR for a special interrupt that is raised when a write was ignored. Unfortunately, interrupts are typically disabled prior to performing a sequence of register writes that include the LCR so the point at which the retry occurs is too late. An example is serial8250_do_set_termios() where an ignored LCR write results in the baud divisor not being set and instead a garbage character is sent out the transmitter. Furthermore, since serial_port_out() offers no way to indicate failure, a serious effort must be made to ensure that the LCR is actually updated before returning back to the caller. This is difficult, however, as a UART that was busy during the first attempt is likely to still be busy when a subsequent attempt is made unless some extra action is taken. This updated workaround reads back the LCR after each write to confirm that the new value was accepted by the hardware. Should the hardware ignore a write, the TX/RX FIFOs are cleared and the receive buffer read before attempting to rewrite the LCR out of the hope that doing so will force the UART into an idle state. While this may seem unnecessarily aggressive, writes to the LCR are used to change the baud rate, parity, stop bit, or data length so the data that may be lost is likely not important. Admittedly, this is far from ideal but it seems to be the best that can be done given the hardware limitations. Lastly, the revised workaround doesn't touch the LCR in the ISR, so it avoids the possibility of a "serial8250: too much work for irq" lock up. This problem is rare in real situations but can be reproduced easily by wiring up two UARTs and running the following commands. # stty -F /dev/ttyS1 echo # stty -F /dev/ttyS2 echo # cat /dev/ttyS1 & [1] 375 # echo asdf > /dev/ttyS1 asdf [ 27.700000] serial8250: too much work for irq96 [ 27.700000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.740000] serial8250: too much work for irq96 Signed-off-by: Tim Kryger <tim.kryger@linaro.org> Reviewed-by: Matt Porter <matt.porter@linaro.org> Reviewed-by: Markus Mayer <markus.mayer@linaro.org> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-10-01 17:18:08 +00:00
/* Make sure LCR write wasn't ignored */
if (offset == UART_LCR) {
int tries = 1000;
while (tries--) {
unsigned int lcr = p->serial_in(p, UART_LCR);
if ((value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR))
serial: 8250_dw: Improve unwritable LCR workaround When configured with UART_16550_COMPATIBLE=NO or in versions prior to the introduction of this option, the Designware UART will ignore writes to the LCR if the UART is busy. The current workaround saves a copy of the last written LCR and re-writes it in the ISR for a special interrupt that is raised when a write was ignored. Unfortunately, interrupts are typically disabled prior to performing a sequence of register writes that include the LCR so the point at which the retry occurs is too late. An example is serial8250_do_set_termios() where an ignored LCR write results in the baud divisor not being set and instead a garbage character is sent out the transmitter. Furthermore, since serial_port_out() offers no way to indicate failure, a serious effort must be made to ensure that the LCR is actually updated before returning back to the caller. This is difficult, however, as a UART that was busy during the first attempt is likely to still be busy when a subsequent attempt is made unless some extra action is taken. This updated workaround reads back the LCR after each write to confirm that the new value was accepted by the hardware. Should the hardware ignore a write, the TX/RX FIFOs are cleared and the receive buffer read before attempting to rewrite the LCR out of the hope that doing so will force the UART into an idle state. While this may seem unnecessarily aggressive, writes to the LCR are used to change the baud rate, parity, stop bit, or data length so the data that may be lost is likely not important. Admittedly, this is far from ideal but it seems to be the best that can be done given the hardware limitations. Lastly, the revised workaround doesn't touch the LCR in the ISR, so it avoids the possibility of a "serial8250: too much work for irq" lock up. This problem is rare in real situations but can be reproduced easily by wiring up two UARTs and running the following commands. # stty -F /dev/ttyS1 echo # stty -F /dev/ttyS2 echo # cat /dev/ttyS1 & [1] 375 # echo asdf > /dev/ttyS1 asdf [ 27.700000] serial8250: too much work for irq96 [ 27.700000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.740000] serial8250: too much work for irq96 Signed-off-by: Tim Kryger <tim.kryger@linaro.org> Reviewed-by: Matt Porter <matt.porter@linaro.org> Reviewed-by: Markus Mayer <markus.mayer@linaro.org> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-10-01 17:18:08 +00:00
return;
dw8250_force_idle(p);
writel(value, p->membase + (UART_LCR << p->regshift));
}
/*
* FIXME: this deadlocks if port->lock is already held
* dev_err(p->dev, "Couldn't set LCR to %d\n", value);
*/
serial: 8250_dw: Improve unwritable LCR workaround When configured with UART_16550_COMPATIBLE=NO or in versions prior to the introduction of this option, the Designware UART will ignore writes to the LCR if the UART is busy. The current workaround saves a copy of the last written LCR and re-writes it in the ISR for a special interrupt that is raised when a write was ignored. Unfortunately, interrupts are typically disabled prior to performing a sequence of register writes that include the LCR so the point at which the retry occurs is too late. An example is serial8250_do_set_termios() where an ignored LCR write results in the baud divisor not being set and instead a garbage character is sent out the transmitter. Furthermore, since serial_port_out() offers no way to indicate failure, a serious effort must be made to ensure that the LCR is actually updated before returning back to the caller. This is difficult, however, as a UART that was busy during the first attempt is likely to still be busy when a subsequent attempt is made unless some extra action is taken. This updated workaround reads back the LCR after each write to confirm that the new value was accepted by the hardware. Should the hardware ignore a write, the TX/RX FIFOs are cleared and the receive buffer read before attempting to rewrite the LCR out of the hope that doing so will force the UART into an idle state. While this may seem unnecessarily aggressive, writes to the LCR are used to change the baud rate, parity, stop bit, or data length so the data that may be lost is likely not important. Admittedly, this is far from ideal but it seems to be the best that can be done given the hardware limitations. Lastly, the revised workaround doesn't touch the LCR in the ISR, so it avoids the possibility of a "serial8250: too much work for irq" lock up. This problem is rare in real situations but can be reproduced easily by wiring up two UARTs and running the following commands. # stty -F /dev/ttyS1 echo # stty -F /dev/ttyS2 echo # cat /dev/ttyS1 & [1] 375 # echo asdf > /dev/ttyS1 asdf [ 27.700000] serial8250: too much work for irq96 [ 27.700000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.740000] serial8250: too much work for irq96 Signed-off-by: Tim Kryger <tim.kryger@linaro.org> Reviewed-by: Matt Porter <matt.porter@linaro.org> Reviewed-by: Markus Mayer <markus.mayer@linaro.org> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-10-01 17:18:08 +00:00
}
}
static unsigned int dw8250_serial_in32(struct uart_port *p, int offset)
{
unsigned int value = readl(p->membase + (offset << p->regshift));
return dw8250_modify_msr(p, offset, value);
}
static int dw8250_handle_irq(struct uart_port *p)
{
struct dw8250_data *d = p->private_data;
unsigned int iir = p->serial_in(p, UART_IIR);
if (serial8250_handle_irq(p, iir)) {
return 1;
} else if ((iir & UART_IIR_BUSY) == UART_IIR_BUSY) {
serial: 8250_dw: Improve unwritable LCR workaround When configured with UART_16550_COMPATIBLE=NO or in versions prior to the introduction of this option, the Designware UART will ignore writes to the LCR if the UART is busy. The current workaround saves a copy of the last written LCR and re-writes it in the ISR for a special interrupt that is raised when a write was ignored. Unfortunately, interrupts are typically disabled prior to performing a sequence of register writes that include the LCR so the point at which the retry occurs is too late. An example is serial8250_do_set_termios() where an ignored LCR write results in the baud divisor not being set and instead a garbage character is sent out the transmitter. Furthermore, since serial_port_out() offers no way to indicate failure, a serious effort must be made to ensure that the LCR is actually updated before returning back to the caller. This is difficult, however, as a UART that was busy during the first attempt is likely to still be busy when a subsequent attempt is made unless some extra action is taken. This updated workaround reads back the LCR after each write to confirm that the new value was accepted by the hardware. Should the hardware ignore a write, the TX/RX FIFOs are cleared and the receive buffer read before attempting to rewrite the LCR out of the hope that doing so will force the UART into an idle state. While this may seem unnecessarily aggressive, writes to the LCR are used to change the baud rate, parity, stop bit, or data length so the data that may be lost is likely not important. Admittedly, this is far from ideal but it seems to be the best that can be done given the hardware limitations. Lastly, the revised workaround doesn't touch the LCR in the ISR, so it avoids the possibility of a "serial8250: too much work for irq" lock up. This problem is rare in real situations but can be reproduced easily by wiring up two UARTs and running the following commands. # stty -F /dev/ttyS1 echo # stty -F /dev/ttyS2 echo # cat /dev/ttyS1 & [1] 375 # echo asdf > /dev/ttyS1 asdf [ 27.700000] serial8250: too much work for irq96 [ 27.700000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.710000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.720000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.730000] serial8250: too much work for irq96 [ 27.740000] serial8250: too much work for irq96 Signed-off-by: Tim Kryger <tim.kryger@linaro.org> Reviewed-by: Matt Porter <matt.porter@linaro.org> Reviewed-by: Markus Mayer <markus.mayer@linaro.org> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-10-01 17:18:08 +00:00
/* Clear the USR */
(void)p->serial_in(p, d->usr_reg);
return 1;
}
return 0;
}
static void
dw8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
{
if (!state)
pm_runtime_get_sync(port->dev);
serial8250_do_pm(port, state, old);
if (state)
pm_runtime_put_sync_suspend(port->dev);
}
static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
struct ktermios *old)
{
unsigned int baud = tty_termios_baud_rate(termios);
struct dw8250_data *d = p->private_data;
unsigned int rate;
int ret;
if (IS_ERR(d->clk) || !old)
goto out;
/* Not requesting clock rates below 1.8432Mhz */
if (baud < 115200)
baud = 115200;
clk_disable_unprepare(d->clk);
rate = clk_round_rate(d->clk, baud * 16);
ret = clk_set_rate(d->clk, rate);
clk_prepare_enable(d->clk);
if (!ret)
p->uartclk = rate;
p->status &= ~UPSTAT_AUTOCTS;
if (termios->c_cflag & CRTSCTS)
p->status |= UPSTAT_AUTOCTS;
out:
serial8250_do_set_termios(p, termios, old);
}
static bool dw8250_dma_filter(struct dma_chan *chan, void *param)
{
return false;
}
static void dw8250_setup_port(struct uart_8250_port *up)
{
struct uart_port *p = &up->port;
u32 reg = readl(p->membase + DW_UART_UCV);
/*
* If the Component Version Register returns zero, we know that
* ADDITIONAL_FEATURES are not enabled. No need to go any further.
*/
if (!reg)
return;
dev_dbg_ratelimited(p->dev, "Designware UART version %c.%c%c\n",
(reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff);
reg = readl(p->membase + DW_UART_CPR);
if (!reg)
return;
/* Select the type based on fifo */
if (reg & DW_UART_CPR_FIFO_MODE) {
p->type = PORT_16550A;
p->flags |= UPF_FIXED_TYPE;
p->fifosize = DW_UART_CPR_FIFO_SIZE(reg);
up->tx_loadsz = p->fifosize;
up->capabilities = UART_CAP_FIFO;
}
if (reg & DW_UART_CPR_AFCE_MODE)
up->capabilities |= UART_CAP_AFE;
}
static int dw8250_probe_of(struct uart_port *p,
struct dw8250_data *data)
{
struct device_node *np = p->dev->of_node;
struct uart_8250_port *up = up_to_u8250p(p);
u32 val;
bool has_ucv = true;
int id;
#ifdef CONFIG_64BIT
if (of_device_is_compatible(np, "cavium,octeon-3860-uart")) {
p->serial_in = dw8250_serial_inq;
p->serial_out = dw8250_serial_outq;
p->flags = UPF_SKIP_TEST | UPF_SHARE_IRQ | UPF_FIXED_TYPE;
p->type = PORT_OCTEON;
data->usr_reg = 0x27;
has_ucv = false;
} else
#endif
if (!of_property_read_u32(np, "reg-io-width", &val)) {
switch (val) {
case 1:
break;
case 4:
p->iotype = UPIO_MEM32;
p->serial_in = dw8250_serial_in32;
p->serial_out = dw8250_serial_out32;
break;
default:
dev_err(p->dev, "unsupported reg-io-width (%u)\n", val);
return -EINVAL;
}
}
if (has_ucv)
dw8250_setup_port(up);
/* if we have a valid fifosize, try hooking up DMA here */
if (p->fifosize) {
up->dma = &data->dma;
up->dma->rxconf.src_maxburst = p->fifosize / 4;
up->dma->txconf.dst_maxburst = p->fifosize / 4;
}
if (!of_property_read_u32(np, "reg-shift", &val))
p->regshift = val;
/* get index of serial line, if found in DT aliases */
id = of_alias_get_id(np, "serial");
if (id >= 0)
p->line = id;
if (of_property_read_bool(np, "dcd-override")) {
/* Always report DCD as active */
data->msr_mask_on |= UART_MSR_DCD;
data->msr_mask_off |= UART_MSR_DDCD;
}
if (of_property_read_bool(np, "dsr-override")) {
/* Always report DSR as active */
data->msr_mask_on |= UART_MSR_DSR;
data->msr_mask_off |= UART_MSR_DDSR;
}
if (of_property_read_bool(np, "cts-override")) {
/* Always report CTS as active */
data->msr_mask_on |= UART_MSR_CTS;
data->msr_mask_off |= UART_MSR_DCTS;
}
if (of_property_read_bool(np, "ri-override")) {
/* Always report Ring indicator as inactive */
data->msr_mask_off |= UART_MSR_RI;
data->msr_mask_off |= UART_MSR_TERI;
}
return 0;
}
static bool dw8250_idma_filter(struct dma_chan *chan, void *param)
{
struct device *dev = param;
if (dev != chan->device->dev->parent)
return false;
return true;
}
static int dw8250_probe_acpi(struct uart_8250_port *up,
struct dw8250_data *data)
{
struct uart_port *p = &up->port;
dw8250_setup_port(up);
p->iotype = UPIO_MEM32;
p->serial_in = dw8250_serial_in32;
p->serial_out = dw8250_serial_out32;
p->regshift = 2;
/* Platforms with iDMA */
if (platform_get_resource_byname(to_platform_device(up->port.dev),
IORESOURCE_MEM, "lpss_priv")) {
data->dma.rx_param = up->port.dev->parent;
data->dma.tx_param = up->port.dev->parent;
data->dma.fn = dw8250_idma_filter;
}
up->dma = &data->dma;
up->dma->rxconf.src_maxburst = p->fifosize / 4;
up->dma->txconf.dst_maxburst = p->fifosize / 4;
up->port.set_termios = dw8250_set_termios;
return 0;
}
static int dw8250_probe(struct platform_device *pdev)
{
struct uart_8250_port uart = {};
struct resource *regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
int irq = platform_get_irq(pdev, 0);
struct uart_port *p = &uart.port;
struct dw8250_data *data;
int err;
if (!regs) {
dev_err(&pdev->dev, "no registers defined\n");
return -EINVAL;
}
if (irq < 0) {
if (irq != -EPROBE_DEFER)
dev_err(&pdev->dev, "cannot get irq\n");
return irq;
}
spin_lock_init(&p->lock);
p->mapbase = regs->start;
p->irq = irq;
p->handle_irq = dw8250_handle_irq;
p->pm = dw8250_do_pm;
p->type = PORT_8250;
p->flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_FIXED_PORT;
p->dev = &pdev->dev;
p->iotype = UPIO_MEM;
p->serial_in = dw8250_serial_in;
p->serial_out = dw8250_serial_out;
p->membase = devm_ioremap(&pdev->dev, regs->start, resource_size(regs));
if (!p->membase)
return -ENOMEM;
data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;
data->usr_reg = DW_UART_USR;
p->private_data = data;
/* Always ask for fixed clock rate from a property. */
device_property_read_u32(p->dev, "clock-frequency", &p->uartclk);
/* If there is separate baudclk, get the rate from it. */
data->clk = devm_clk_get(&pdev->dev, "baudclk");
if (IS_ERR(data->clk) && PTR_ERR(data->clk) != -EPROBE_DEFER)
data->clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(data->clk) && PTR_ERR(data->clk) == -EPROBE_DEFER)
return -EPROBE_DEFER;
if (!IS_ERR_OR_NULL(data->clk)) {
err = clk_prepare_enable(data->clk);
if (err)
dev_warn(&pdev->dev, "could not enable optional baudclk: %d\n",
err);
else
p->uartclk = clk_get_rate(data->clk);
}
/* If no clock rate is defined, fail. */
if (!p->uartclk) {
dev_err(&pdev->dev, "clock rate not defined\n");
return -EINVAL;
}
data->pclk = devm_clk_get(&pdev->dev, "apb_pclk");
if (IS_ERR(data->clk) && PTR_ERR(data->clk) == -EPROBE_DEFER) {
err = -EPROBE_DEFER;
goto err_clk;
}
if (!IS_ERR(data->pclk)) {
err = clk_prepare_enable(data->pclk);
if (err) {
dev_err(&pdev->dev, "could not enable apb_pclk\n");
goto err_clk;
}
}
data->rst = devm_reset_control_get_optional(&pdev->dev, NULL);
if (IS_ERR(data->rst) && PTR_ERR(data->rst) == -EPROBE_DEFER) {
err = -EPROBE_DEFER;
goto err_pclk;
}
if (!IS_ERR(data->rst))
reset_control_deassert(data->rst);
data->dma.rx_param = data;
data->dma.tx_param = data;
data->dma.fn = dw8250_dma_filter;
if (pdev->dev.of_node) {
err = dw8250_probe_of(p, data);
if (err)
goto err_reset;
} else if (ACPI_HANDLE(&pdev->dev)) {
err = dw8250_probe_acpi(&uart, data);
if (err)
goto err_reset;
} else {
err = -ENODEV;
goto err_reset;
}
data->line = serial8250_register_8250_port(&uart);
if (data->line < 0) {
err = data->line;
goto err_reset;
}
platform_set_drvdata(pdev, data);
pm_runtime_set_active(&pdev->dev);
pm_runtime_enable(&pdev->dev);
return 0;
err_reset:
if (!IS_ERR(data->rst))
reset_control_assert(data->rst);
err_pclk:
if (!IS_ERR(data->pclk))
clk_disable_unprepare(data->pclk);
err_clk:
if (!IS_ERR(data->clk))
clk_disable_unprepare(data->clk);
return err;
}
static int dw8250_remove(struct platform_device *pdev)
{
struct dw8250_data *data = platform_get_drvdata(pdev);
pm_runtime_get_sync(&pdev->dev);
serial8250_unregister_port(data->line);
if (!IS_ERR(data->rst))
reset_control_assert(data->rst);
if (!IS_ERR(data->pclk))
clk_disable_unprepare(data->pclk);
if (!IS_ERR(data->clk))
clk_disable_unprepare(data->clk);
pm_runtime_disable(&pdev->dev);
pm_runtime_put_noidle(&pdev->dev);
return 0;
}
#ifdef CONFIG_PM_SLEEP
static int dw8250_suspend(struct device *dev)
{
struct dw8250_data *data = dev_get_drvdata(dev);
serial8250_suspend_port(data->line);
return 0;
}
static int dw8250_resume(struct device *dev)
{
struct dw8250_data *data = dev_get_drvdata(dev);
serial8250_resume_port(data->line);
return 0;
}
#endif /* CONFIG_PM_SLEEP */
#ifdef CONFIG_PM
static int dw8250_runtime_suspend(struct device *dev)
{
struct dw8250_data *data = dev_get_drvdata(dev);
if (!IS_ERR(data->clk))
clk_disable_unprepare(data->clk);
if (!IS_ERR(data->pclk))
clk_disable_unprepare(data->pclk);
return 0;
}
static int dw8250_runtime_resume(struct device *dev)
{
struct dw8250_data *data = dev_get_drvdata(dev);
if (!IS_ERR(data->pclk))
clk_prepare_enable(data->pclk);
if (!IS_ERR(data->clk))
clk_prepare_enable(data->clk);
return 0;
}
#endif
static const struct dev_pm_ops dw8250_pm_ops = {
SET_SYSTEM_SLEEP_PM_OPS(dw8250_suspend, dw8250_resume)
SET_RUNTIME_PM_OPS(dw8250_runtime_suspend, dw8250_runtime_resume, NULL)
};
static const struct of_device_id dw8250_of_match[] = {
{ .compatible = "snps,dw-apb-uart" },
{ .compatible = "cavium,octeon-3860-uart" },
{ /* Sentinel */ }
};
MODULE_DEVICE_TABLE(of, dw8250_of_match);
static const struct acpi_device_id dw8250_acpi_match[] = {
{ "INT33C4", 0 },
{ "INT33C5", 0 },
{ "INT3434", 0 },
{ "INT3435", 0 },
{ "80860F0A", 0 },
{ "8086228A", 0 },
{ "APMC0D08", 0},
{ "AMD0020", 0 },
{ },
};
MODULE_DEVICE_TABLE(acpi, dw8250_acpi_match);
static struct platform_driver dw8250_platform_driver = {
.driver = {
.name = "dw-apb-uart",
.pm = &dw8250_pm_ops,
.of_match_table = dw8250_of_match,
.acpi_match_table = ACPI_PTR(dw8250_acpi_match),
},
.probe = dw8250_probe,
.remove = dw8250_remove,
};
module_platform_driver(dw8250_platform_driver);
MODULE_AUTHOR("Jamie Iles");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Synopsys DesignWare 8250 serial port driver");
MODULE_ALIAS("platform:dw-apb-uart");