diff options
Diffstat (limited to 'debian/patches-rt/serial__8250__implement_write_atomic.patch')
| -rw-r--r-- | debian/patches-rt/serial__8250__implement_write_atomic.patch | 485 |
1 files changed, 485 insertions, 0 deletions
diff --git a/debian/patches-rt/serial__8250__implement_write_atomic.patch b/debian/patches-rt/serial__8250__implement_write_atomic.patch new file mode 100644 index 000000000..d872f47fd --- /dev/null +++ b/debian/patches-rt/serial__8250__implement_write_atomic.patch @@ -0,0 +1,485 @@ +Subject: serial: 8250: implement write_atomic +From: John Ogness <john.ogness@linutronix.de> +Date: Mon Nov 30 01:42:02 2020 +0106 +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.15/older/patches-5.15.3-rt21.tar.xz + +From: John Ogness <john.ogness@linutronix.de> + +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: Thomas Gleixner <tglx@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(-) +--- +--- a/drivers/tty/serial/8250/8250.h ++++ b/drivers/tty/serial/8250/8250.h +@@ -132,12 +132,55 @@ static inline void serial_dl_write(struc + 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 long 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 long flags; ++ unsigned int prior; ++ 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; + } + +@@ -146,7 +189,7 @@ static inline bool serial8250_clear_THRI + 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; + } + +--- a/drivers/tty/serial/8250/8250_core.c ++++ b/drivers/tty/serial/8250/8250_core.c +@@ -264,10 +264,8 @@ static void serial8250_backup_timeout(st + * 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); + +@@ -290,7 +288,7 @@ static void serial8250_backup_timeout(st + 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); + +@@ -568,6 +566,14 @@ serial8250_register_ports(struct uart_dr + + #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) + { +@@ -661,6 +667,7 @@ static int univ8250_console_match(struct + + 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, +--- 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 + + /* Stop processing interrupts on input overrun */ + if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) { ++ unsigned long flags; + unsigned long delay; ++ bool is_console; + ++ is_console = uart_console(port); ++ ++ if (is_console) ++ console_atomic_lock(flags); + up->ier = port->serial_in(port, UART_IER); ++ if (is_console) ++ console_atomic_unlock(flags); ++ + if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) { + port->ops->stop_rx(port); + } else { +--- 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 + + static void ingenic_uart_serial_out(struct uart_port *p, int offset, int value) + { ++ unsigned long flags; ++ bool is_console; + int ier; + + switch (offset) { +@@ -167,7 +169,12 @@ static void ingenic_uart_serial_out(stru + * 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; +--- a/drivers/tty/serial/8250/8250_mtk.c ++++ b/drivers/tty/serial/8250/8250_mtk.c +@@ -218,12 +218,37 @@ static void mtk8250_shutdown(struct uart + + 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 long 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 long 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) +--- a/drivers/tty/serial/8250/8250_port.c ++++ b/drivers/tty/serial/8250/8250_port.c +@@ -762,7 +762,7 @@ static void serial8250_set_sleep(struct + 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); +@@ -1436,7 +1436,7 @@ static void serial8250_stop_rx(struct ua + + 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); + } +@@ -1466,7 +1466,7 @@ void serial8250_em485_stop_tx(struct uar + 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); +@@ -1688,7 +1688,7 @@ static void serial8250_disable_ms(struct + 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) +@@ -1704,7 +1704,7 @@ static void serial8250_enable_ms(struct + 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); + } + +@@ -2132,14 +2132,7 @@ static void serial8250_put_poll_char(str + 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); + /* +@@ -2152,7 +2145,7 @@ static void serial8250_put_poll_char(str + * 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); + } + +@@ -2455,7 +2448,7 @@ void serial8250_do_shutdown(struct uart_ + */ + 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); +@@ -2824,7 +2817,7 @@ serial8250_do_set_termios(struct uart_po + 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; +@@ -3290,7 +3283,7 @@ EXPORT_SYMBOL_GPL(serial8250_set_default + + #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); + +@@ -3298,6 +3291,18 @@ static void serial8250_console_putchar(s + 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 long 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 + */ +@@ -3319,6 +3324,32 @@ static void serial8250_console_restore(s + serial8250_out_MCR(up, 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 long 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... +@@ -3335,24 +3366,12 @@ void serial8250_console_write(struct uar + 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))) { +@@ -3366,7 +3385,9 @@ void serial8250_console_write(struct uar + 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 +@@ -3379,8 +3400,7 @@ void serial8250_console_write(struct uar + 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 +@@ -3392,8 +3412,7 @@ void serial8250_console_write(struct uar + 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) +@@ -3413,6 +3432,7 @@ static unsigned int probe_baud(struct ua + + 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'; +@@ -3422,6 +3442,8 @@ int serial8250_console_setup(struct uart + 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) +--- 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_82 + 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); + |