diff options
Diffstat (limited to 'debian/patches-rt/0100-serial-8250-implement-write_atomic.patch')
| -rw-r--r-- | debian/patches-rt/0100-serial-8250-implement-write_atomic.patch | 500 |
1 files changed, 500 insertions, 0 deletions
diff --git a/debian/patches-rt/0100-serial-8250-implement-write_atomic.patch b/debian/patches-rt/0100-serial-8250-implement-write_atomic.patch new file mode 100644 index 000000000..ad692ff78 --- /dev/null +++ b/debian/patches-rt/0100-serial-8250-implement-write_atomic.patch @@ -0,0 +1,500 @@ +From 713182575337acb0891fcfaef75c3a36408d1766 Mon Sep 17 00:00:00 2001 +From: John Ogness <john.ogness@linutronix.de> +Date: Mon, 30 Nov 2020 01:42:02 +0106 +Subject: [PATCH 100/323] serial: 8250: implement write_atomic +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz + +Implement a non-sleeping NMI-safe write_atomic() console function in +order to support emergency console printing. + +Since interrupts need to be disabled during transmit, all usage of +the IER register is wrapped with access functions that use the +console_atomic_lock() function to synchronize register access while +tracking the state of the interrupts. This is necessary because +write_atomic() can be called from an NMI context that has preempted +write_atomic(). + +Signed-off-by: John Ogness <john.ogness@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + drivers/tty/serial/8250/8250.h | 47 ++++++++++++- + drivers/tty/serial/8250/8250_core.c | 17 +++-- + drivers/tty/serial/8250/8250_fsl.c | 9 +++ + drivers/tty/serial/8250/8250_ingenic.c | 7 ++ + drivers/tty/serial/8250/8250_mtk.c | 29 +++++++- + drivers/tty/serial/8250/8250_port.c | 92 ++++++++++++++++---------- + include/linux/serial_8250.h | 5 ++ + 7 files changed, 162 insertions(+), 44 deletions(-) + +diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h +index 61b11490ae5b..32c534b87397 100644 +--- a/drivers/tty/serial/8250/8250.h ++++ b/drivers/tty/serial/8250/8250.h +@@ -152,12 +152,55 @@ static inline void serial_dl_write(struct uart_8250_port *up, int value) + up->dl_write(up, value); + } + ++static inline void serial8250_set_IER(struct uart_8250_port *up, ++ unsigned char ier) ++{ ++ struct uart_port *port = &up->port; ++ unsigned int flags; ++ bool is_console; ++ ++ is_console = uart_console(port); ++ ++ if (is_console) ++ console_atomic_lock(&flags); ++ ++ serial_out(up, UART_IER, ier); ++ ++ if (is_console) ++ console_atomic_unlock(flags); ++} ++ ++static inline unsigned char serial8250_clear_IER(struct uart_8250_port *up) ++{ ++ struct uart_port *port = &up->port; ++ unsigned int clearval = 0; ++ unsigned int prior; ++ unsigned int flags; ++ bool is_console; ++ ++ is_console = uart_console(port); ++ ++ if (up->capabilities & UART_CAP_UUE) ++ clearval = UART_IER_UUE; ++ ++ if (is_console) ++ console_atomic_lock(&flags); ++ ++ prior = serial_port_in(port, UART_IER); ++ serial_port_out(port, UART_IER, clearval); ++ ++ if (is_console) ++ console_atomic_unlock(flags); ++ ++ return prior; ++} ++ + static inline bool serial8250_set_THRI(struct uart_8250_port *up) + { + if (up->ier & UART_IER_THRI) + return false; + up->ier |= UART_IER_THRI; +- serial_out(up, UART_IER, up->ier); ++ serial8250_set_IER(up, up->ier); + return true; + } + +@@ -166,7 +209,7 @@ static inline bool serial8250_clear_THRI(struct uart_8250_port *up) + if (!(up->ier & UART_IER_THRI)) + return false; + up->ier &= ~UART_IER_THRI; +- serial_out(up, UART_IER, up->ier); ++ serial8250_set_IER(up, up->ier); + return true; + } + +diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c +index 43f2eed6df78..687119fe2f8c 100644 +--- a/drivers/tty/serial/8250/8250_core.c ++++ b/drivers/tty/serial/8250/8250_core.c +@@ -275,10 +275,8 @@ static void serial8250_backup_timeout(struct timer_list *t) + * Must disable interrupts or else we risk racing with the interrupt + * based handler. + */ +- if (up->port.irq) { +- ier = serial_in(up, UART_IER); +- serial_out(up, UART_IER, 0); +- } ++ if (up->port.irq) ++ ier = serial8250_clear_IER(up); + + iir = serial_in(up, UART_IIR); + +@@ -301,7 +299,7 @@ static void serial8250_backup_timeout(struct timer_list *t) + serial8250_tx_chars(up); + + if (up->port.irq) +- serial_out(up, UART_IER, ier); ++ serial8250_set_IER(up, ier); + + spin_unlock_irqrestore(&up->port.lock, flags); + +@@ -588,6 +586,14 @@ serial8250_register_ports(struct uart_driver *drv, struct device *dev) + + #ifdef CONFIG_SERIAL_8250_CONSOLE + ++static void univ8250_console_write_atomic(struct console *co, const char *s, ++ unsigned int count) ++{ ++ struct uart_8250_port *up = &serial8250_ports[co->index]; ++ ++ serial8250_console_write_atomic(up, s, count); ++} ++ + static void univ8250_console_write(struct console *co, const char *s, + unsigned int count) + { +@@ -681,6 +687,7 @@ static int univ8250_console_match(struct console *co, char *name, int idx, + + static struct console univ8250_console = { + .name = "ttyS", ++ .write_atomic = univ8250_console_write_atomic, + .write = univ8250_console_write, + .device = uart_console_device, + .setup = univ8250_console_setup, +diff --git a/drivers/tty/serial/8250/8250_fsl.c b/drivers/tty/serial/8250/8250_fsl.c +index fbcc90c31ca1..b33cb454ce03 100644 +--- a/drivers/tty/serial/8250/8250_fsl.c ++++ b/drivers/tty/serial/8250/8250_fsl.c +@@ -60,9 +60,18 @@ int fsl8250_handle_irq(struct uart_port *port) + + /* Stop processing interrupts on input overrun */ + if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) { ++ unsigned int ca_flags; + unsigned long delay; ++ bool is_console; + ++ is_console = uart_console(port); ++ ++ if (is_console) ++ console_atomic_lock(&ca_flags); + up->ier = port->serial_in(port, UART_IER); ++ if (is_console) ++ console_atomic_unlock(ca_flags); ++ + if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) { + port->ops->stop_rx(port); + } else { +diff --git a/drivers/tty/serial/8250/8250_ingenic.c b/drivers/tty/serial/8250/8250_ingenic.c +index 988bf6bcce42..bcd26d672539 100644 +--- a/drivers/tty/serial/8250/8250_ingenic.c ++++ b/drivers/tty/serial/8250/8250_ingenic.c +@@ -146,6 +146,8 @@ OF_EARLYCON_DECLARE(x1000_uart, "ingenic,x1000-uart", + + static void ingenic_uart_serial_out(struct uart_port *p, int offset, int value) + { ++ unsigned int flags; ++ bool is_console; + int ier; + + switch (offset) { +@@ -167,7 +169,12 @@ static void ingenic_uart_serial_out(struct uart_port *p, int offset, int value) + * If we have enabled modem status IRQs we should enable + * modem mode. + */ ++ is_console = uart_console(p); ++ if (is_console) ++ console_atomic_lock(&flags); + ier = p->serial_in(p, UART_IER); ++ if (is_console) ++ console_atomic_unlock(flags); + + if (ier & UART_IER_MSI) + value |= UART_MCR_MDCE | UART_MCR_FCM; +diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c +index de48a58460f4..d246f2755fed 100644 +--- a/drivers/tty/serial/8250/8250_mtk.c ++++ b/drivers/tty/serial/8250/8250_mtk.c +@@ -222,12 +222,37 @@ static void mtk8250_shutdown(struct uart_port *port) + + static void mtk8250_disable_intrs(struct uart_8250_port *up, int mask) + { +- serial_out(up, UART_IER, serial_in(up, UART_IER) & (~mask)); ++ struct uart_port *port = &up->port; ++ unsigned int flags; ++ unsigned int ier; ++ bool is_console; ++ ++ is_console = uart_console(port); ++ ++ if (is_console) ++ console_atomic_lock(&flags); ++ ++ ier = serial_in(up, UART_IER); ++ serial_out(up, UART_IER, ier & (~mask)); ++ ++ if (is_console) ++ console_atomic_unlock(flags); + } + + static void mtk8250_enable_intrs(struct uart_8250_port *up, int mask) + { +- serial_out(up, UART_IER, serial_in(up, UART_IER) | mask); ++ struct uart_port *port = &up->port; ++ unsigned int flags; ++ unsigned int ier; ++ ++ if (uart_console(port)) ++ console_atomic_lock(&flags); ++ ++ ier = serial_in(up, UART_IER); ++ serial_out(up, UART_IER, ier | mask); ++ ++ if (uart_console(port)) ++ console_atomic_unlock(flags); + } + + static void mtk8250_set_flow_ctrl(struct uart_8250_port *up, int mode) +diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c +index 8b49ac4856d2..947737d0e46b 100644 +--- a/drivers/tty/serial/8250/8250_port.c ++++ b/drivers/tty/serial/8250/8250_port.c +@@ -730,7 +730,7 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) + serial_out(p, UART_EFR, UART_EFR_ECB); + serial_out(p, UART_LCR, 0); + } +- serial_out(p, UART_IER, sleep ? UART_IERX_SLEEP : 0); ++ serial8250_set_IER(p, sleep ? UART_IERX_SLEEP : 0); + if (p->capabilities & UART_CAP_EFR) { + serial_out(p, UART_LCR, UART_LCR_CONF_MODE_B); + serial_out(p, UART_EFR, efr); +@@ -1405,7 +1405,7 @@ static void serial8250_stop_rx(struct uart_port *port) + + up->ier &= ~(UART_IER_RLSI | UART_IER_RDI); + up->port.read_status_mask &= ~UART_LSR_DR; +- serial_port_out(port, UART_IER, up->ier); ++ serial8250_set_IER(up, up->ier); + + serial8250_rpm_put(up); + } +@@ -1435,7 +1435,7 @@ void serial8250_em485_stop_tx(struct uart_8250_port *p) + serial8250_clear_and_reinit_fifos(p); + + p->ier |= UART_IER_RLSI | UART_IER_RDI; +- serial_port_out(&p->port, UART_IER, p->ier); ++ serial8250_set_IER(p, p->ier); + } + } + EXPORT_SYMBOL_GPL(serial8250_em485_stop_tx); +@@ -1677,7 +1677,7 @@ static void serial8250_disable_ms(struct uart_port *port) + mctrl_gpio_disable_ms(up->gpios); + + up->ier &= ~UART_IER_MSI; +- serial_port_out(port, UART_IER, up->ier); ++ serial8250_set_IER(up, up->ier); + } + + static void serial8250_enable_ms(struct uart_port *port) +@@ -1693,7 +1693,7 @@ static void serial8250_enable_ms(struct uart_port *port) + up->ier |= UART_IER_MSI; + + serial8250_rpm_get(up); +- serial_port_out(port, UART_IER, up->ier); ++ serial8250_set_IER(up, up->ier); + serial8250_rpm_put(up); + } + +@@ -2129,14 +2129,7 @@ static void serial8250_put_poll_char(struct uart_port *port, + struct uart_8250_port *up = up_to_u8250p(port); + + serial8250_rpm_get(up); +- /* +- * First save the IER then disable the interrupts +- */ +- ier = serial_port_in(port, UART_IER); +- if (up->capabilities & UART_CAP_UUE) +- serial_port_out(port, UART_IER, UART_IER_UUE); +- else +- serial_port_out(port, UART_IER, 0); ++ ier = serial8250_clear_IER(up); + + wait_for_xmitr(up, BOTH_EMPTY); + /* +@@ -2149,7 +2142,7 @@ static void serial8250_put_poll_char(struct uart_port *port, + * and restore the IER + */ + wait_for_xmitr(up, BOTH_EMPTY); +- serial_port_out(port, UART_IER, ier); ++ serial8250_set_IER(up, ier); + serial8250_rpm_put(up); + } + +@@ -2454,7 +2447,7 @@ void serial8250_do_shutdown(struct uart_port *port) + */ + spin_lock_irqsave(&port->lock, flags); + up->ier = 0; +- serial_port_out(port, UART_IER, 0); ++ serial8250_set_IER(up, 0); + spin_unlock_irqrestore(&port->lock, flags); + + synchronize_irq(port->irq); +@@ -2806,7 +2799,7 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios, + if (up->capabilities & UART_CAP_RTOIE) + up->ier |= UART_IER_RTOIE; + +- serial_port_out(port, UART_IER, up->ier); ++ serial8250_set_IER(up, up->ier); + + if (up->capabilities & UART_CAP_EFR) { + unsigned char efr = 0; +@@ -3271,7 +3264,7 @@ EXPORT_SYMBOL_GPL(serial8250_set_defaults); + + #ifdef CONFIG_SERIAL_8250_CONSOLE + +-static void serial8250_console_putchar(struct uart_port *port, int ch) ++static void serial8250_console_putchar_locked(struct uart_port *port, int ch) + { + struct uart_8250_port *up = up_to_u8250p(port); + +@@ -3279,6 +3272,18 @@ static void serial8250_console_putchar(struct uart_port *port, int ch) + serial_port_out(port, UART_TX, ch); + } + ++static void serial8250_console_putchar(struct uart_port *port, int ch) ++{ ++ struct uart_8250_port *up = up_to_u8250p(port); ++ unsigned int flags; ++ ++ wait_for_xmitr(up, UART_LSR_THRE); ++ ++ console_atomic_lock(&flags); ++ serial8250_console_putchar_locked(port, ch); ++ console_atomic_unlock(flags); ++} ++ + /* + * Restore serial console when h/w power-off detected + */ +@@ -3305,6 +3310,32 @@ static void serial8250_console_restore(struct uart_8250_port *up) + serial8250_out_MCR(up, up->mcr | UART_MCR_DTR | UART_MCR_RTS); + } + ++void serial8250_console_write_atomic(struct uart_8250_port *up, ++ const char *s, unsigned int count) ++{ ++ struct uart_port *port = &up->port; ++ unsigned int flags; ++ unsigned int ier; ++ ++ console_atomic_lock(&flags); ++ ++ touch_nmi_watchdog(); ++ ++ ier = serial8250_clear_IER(up); ++ ++ if (atomic_fetch_inc(&up->console_printing)) { ++ uart_console_write(port, "\n", 1, ++ serial8250_console_putchar_locked); ++ } ++ uart_console_write(port, s, count, serial8250_console_putchar_locked); ++ atomic_dec(&up->console_printing); ++ ++ wait_for_xmitr(up, BOTH_EMPTY); ++ serial8250_set_IER(up, ier); ++ ++ console_atomic_unlock(flags); ++} ++ + /* + * Print a string to the serial port trying not to disturb + * any possible real use of the port... +@@ -3321,24 +3352,12 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, + struct uart_port *port = &up->port; + unsigned long flags; + unsigned int ier; +- int locked = 1; + + touch_nmi_watchdog(); + +- if (oops_in_progress) +- locked = spin_trylock_irqsave(&port->lock, flags); +- else +- spin_lock_irqsave(&port->lock, flags); +- +- /* +- * First save the IER then disable the interrupts +- */ +- ier = serial_port_in(port, UART_IER); ++ spin_lock_irqsave(&port->lock, flags); + +- if (up->capabilities & UART_CAP_UUE) +- serial_port_out(port, UART_IER, UART_IER_UUE); +- else +- serial_port_out(port, UART_IER, 0); ++ ier = serial8250_clear_IER(up); + + /* check scratch reg to see if port powered off during system sleep */ + if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) { +@@ -3352,7 +3371,9 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, + mdelay(port->rs485.delay_rts_before_send); + } + ++ atomic_inc(&up->console_printing); + uart_console_write(port, s, count, serial8250_console_putchar); ++ atomic_dec(&up->console_printing); + + /* + * Finally, wait for transmitter to become empty +@@ -3365,8 +3386,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, + if (em485->tx_stopped) + up->rs485_stop_tx(up); + } +- +- serial_port_out(port, UART_IER, ier); ++ serial8250_set_IER(up, ier); + + /* + * The receive handling will happen properly because the +@@ -3378,8 +3398,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, + if (up->msr_saved_flags) + serial8250_modem_status(up); + +- if (locked) +- spin_unlock_irqrestore(&port->lock, flags); ++ spin_unlock_irqrestore(&port->lock, flags); + } + + static unsigned int probe_baud(struct uart_port *port) +@@ -3399,6 +3418,7 @@ static unsigned int probe_baud(struct uart_port *port) + + int serial8250_console_setup(struct uart_port *port, char *options, bool probe) + { ++ struct uart_8250_port *up = up_to_u8250p(port); + int baud = 9600; + int bits = 8; + int parity = 'n'; +@@ -3408,6 +3428,8 @@ int serial8250_console_setup(struct uart_port *port, char *options, bool probe) + if (!port->iobase && !port->membase) + return -ENODEV; + ++ atomic_set(&up->console_printing, 0); ++ + if (options) + uart_parse_options(options, &baud, &parity, &bits, &flow); + else if (probe) +diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h +index abb928361270..77de68ed2d60 100644 +--- a/include/linux/serial_8250.h ++++ b/include/linux/serial_8250.h +@@ -7,6 +7,7 @@ + #ifndef _LINUX_SERIAL_8250_H + #define _LINUX_SERIAL_8250_H + ++#include <linux/atomic.h> + #include <linux/serial_core.h> + #include <linux/serial_reg.h> + #include <linux/platform_device.h> +@@ -125,6 +126,8 @@ struct uart_8250_port { + #define MSR_SAVE_FLAGS UART_MSR_ANY_DELTA + unsigned char msr_saved_flags; + ++ atomic_t console_printing; ++ + struct uart_8250_dma *dma; + const struct uart_8250_ops *ops; + +@@ -180,6 +183,8 @@ void serial8250_init_port(struct uart_8250_port *up); + void serial8250_set_defaults(struct uart_8250_port *up); + void serial8250_console_write(struct uart_8250_port *up, const char *s, + unsigned int count); ++void serial8250_console_write_atomic(struct uart_8250_port *up, const char *s, ++ unsigned int count); + int serial8250_console_setup(struct uart_port *port, char *options, bool probe); + int serial8250_console_exit(struct uart_port *port); + +-- +2.43.0 + |