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-rw-r--r--debian/patches-rt/0100-serial-8250-implement-write_atomic.patch500
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
+
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-26 11:06:03 +0000