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Message-Id: <20241227224523.28131-5-john.ogness@linutronix.de>
Date: Fri, 27 Dec 2024 23:51:20 +0106
From: John Ogness <john.ogness@...utronix.de>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Slaby <jirislaby@...nel.org>,
Petr Mladek <pmladek@...e.com>,
Sergey Senozhatsky <senozhatsky@...omium.org>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>,
Esben Haabendal <esben@...nix.com>,
linux-serial@...r.kernel.org,
linux-kernel@...r.kernel.org,
Florian Fainelli <florian.fainelli@...adcom.com>,
Ray Jui <rjui@...adcom.com>,
Scott Branden <sbranden@...adcom.com>,
Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Arnd Bergmann <arnd@...db.de>,
Sunil V L <sunilvl@...tanamicro.com>,
Matt Turner <mattst88@...il.com>,
Stefan Wahren <wahrenst@....net>,
Uwe Kleine-König <u.kleine-koenig@...libre.com>,
Kevin Hilman <khilman@...libre.com>,
Markus Schneider-Pargmann <msp@...libre.com>,
Udit Kumar <u-kumar1@...com>,
Griffin Kroah-Hartman <griffin@...ah.com>,
Niklas Schnelle <schnelle@...ux.ibm.com>,
Serge Semin <fancer.lancer@...il.com>,
linux-rpi-kernel@...ts.infradead.org,
linux-arm-kernel@...ts.infradead.org
Subject: [PATCH tty-next v4 4/6] serial: 8250: Provide flag for IER toggling for RS485
For RS485 mode, if SER_RS485_RX_DURING_TX is not available, the
console ->write() callback needs to enable/disable Tx. It does
this by calling the ->rs485_start_tx() and ->rs485_stop_tx()
callbacks. However, some of these callbacks also disable/enable
interrupts and makes power management calls. This causes 2
problems for console writing:
1. A console write can occur in contexts that are illegal for
pm_runtime_*(). It is not even necessary for console writing
to use pm_runtime_*() because a console already does this in
serial8250_console_setup() and serial8250_console_exit().
2. The console ->write() callback already handles
disabling/enabling the interrupts by properly restoring the
previous IER value.
Add an argument @toggle_ier to the ->rs485_start_tx() and
->rs485_stop_tx() callbacks to specify if they may disable/enable
receive interrupts while using pm_runtime_*(). Console writing
will not allow the toggling.
For all call sites other than console writing there is no
functional change.
Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
drivers/tty/serial/8250/8250.h | 4 ++--
drivers/tty/serial/8250/8250_bcm2835aux.c | 4 ++--
drivers/tty/serial/8250/8250_omap.c | 2 +-
drivers/tty/serial/8250/8250_port.c | 26 +++++++++++++----------
include/linux/serial_8250.h | 4 ++--
5 files changed, 22 insertions(+), 18 deletions(-)
diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
index e5310c65cf52..11e05aa014e5 100644
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -231,8 +231,8 @@ void serial8250_rpm_put_tx(struct uart_8250_port *p);
int serial8250_em485_config(struct uart_port *port, struct ktermios *termios,
struct serial_rs485 *rs485);
-void serial8250_em485_start_tx(struct uart_8250_port *p);
-void serial8250_em485_stop_tx(struct uart_8250_port *p);
+void serial8250_em485_start_tx(struct uart_8250_port *p, bool toggle_ier);
+void serial8250_em485_stop_tx(struct uart_8250_port *p, bool toggle_ier);
void serial8250_em485_destroy(struct uart_8250_port *p);
extern struct serial_rs485 serial8250_em485_supported;
diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c
index fdb53b54e99e..0609582a62f7 100644
--- a/drivers/tty/serial/8250/8250_bcm2835aux.c
+++ b/drivers/tty/serial/8250/8250_bcm2835aux.c
@@ -46,7 +46,7 @@ struct bcm2835aux_data {
u32 cntl;
};
-static void bcm2835aux_rs485_start_tx(struct uart_8250_port *up)
+static void bcm2835aux_rs485_start_tx(struct uart_8250_port *up, bool toggle_ier)
{
if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX)) {
struct bcm2835aux_data *data = dev_get_drvdata(up->port.dev);
@@ -65,7 +65,7 @@ static void bcm2835aux_rs485_start_tx(struct uart_8250_port *up)
serial8250_out_MCR(up, UART_MCR_RTS);
}
-static void bcm2835aux_rs485_stop_tx(struct uart_8250_port *up)
+static void bcm2835aux_rs485_stop_tx(struct uart_8250_port *up, bool toggle_ier)
{
if (up->port.rs485.flags & SER_RS485_RTS_AFTER_SEND)
serial8250_out_MCR(up, 0);
diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 42b4aa56b902..c2b75e3f106d 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -365,7 +365,7 @@ static void omap8250_restore_regs(struct uart_8250_port *up)
if (up->port.rs485.flags & SER_RS485_ENABLED &&
up->port.rs485_config == serial8250_em485_config)
- serial8250_em485_stop_tx(up);
+ serial8250_em485_stop_tx(up, true);
}
/*
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 812f003c252d..e38271f477d1 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -578,7 +578,7 @@ static int serial8250_em485_init(struct uart_8250_port *p)
deassert_rts:
if (p->em485->tx_stopped)
- p->rs485_stop_tx(p);
+ p->rs485_stop_tx(p, true);
return 0;
}
@@ -1398,10 +1398,11 @@ static void serial8250_stop_rx(struct uart_port *port)
/**
* serial8250_em485_stop_tx() - generic ->rs485_stop_tx() callback
* @p: uart 8250 port
+ * @toggle_ier: true to allow enabling receive interrupts
*
* Generic callback usable by 8250 uart drivers to stop rs485 transmission.
*/
-void serial8250_em485_stop_tx(struct uart_8250_port *p)
+void serial8250_em485_stop_tx(struct uart_8250_port *p, bool toggle_ier)
{
unsigned char mcr = serial8250_in_MCR(p);
@@ -1422,8 +1423,10 @@ void serial8250_em485_stop_tx(struct uart_8250_port *p)
if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) {
serial8250_clear_and_reinit_fifos(p);
- p->ier |= UART_IER_RLSI | UART_IER_RDI;
- serial_port_out(&p->port, UART_IER, p->ier);
+ if (toggle_ier) {
+ p->ier |= UART_IER_RLSI | UART_IER_RDI;
+ serial_port_out(&p->port, UART_IER, p->ier);
+ }
}
}
EXPORT_SYMBOL_GPL(serial8250_em485_stop_tx);
@@ -1438,7 +1441,7 @@ static enum hrtimer_restart serial8250_em485_handle_stop_tx(struct hrtimer *t)
serial8250_rpm_get(p);
uart_port_lock_irqsave(&p->port, &flags);
if (em485->active_timer == &em485->stop_tx_timer) {
- p->rs485_stop_tx(p);
+ p->rs485_stop_tx(p, true);
em485->active_timer = NULL;
em485->tx_stopped = true;
}
@@ -1470,7 +1473,7 @@ static void __stop_tx_rs485(struct uart_8250_port *p, u64 stop_delay)
em485->active_timer = &em485->stop_tx_timer;
hrtimer_start(&em485->stop_tx_timer, ns_to_ktime(stop_delay), HRTIMER_MODE_REL);
} else {
- p->rs485_stop_tx(p);
+ p->rs485_stop_tx(p, true);
em485->active_timer = NULL;
em485->tx_stopped = true;
}
@@ -1559,6 +1562,7 @@ static inline void __start_tx(struct uart_port *port)
/**
* serial8250_em485_start_tx() - generic ->rs485_start_tx() callback
* @up: uart 8250 port
+ * @toggle_ier: true to allow disabling receive interrupts
*
* Generic callback usable by 8250 uart drivers to start rs485 transmission.
* Assumes that setting the RTS bit in the MCR register means RTS is high.
@@ -1566,11 +1570,11 @@ static inline void __start_tx(struct uart_port *port)
* stoppable by disabling the UART_IER_RDI interrupt. (Some chips set the
* UART_LSR_DR bit even when UART_IER_RDI is disabled, foiling this approach.)
*/
-void serial8250_em485_start_tx(struct uart_8250_port *up)
+void serial8250_em485_start_tx(struct uart_8250_port *up, bool toggle_ier)
{
unsigned char mcr = serial8250_in_MCR(up);
- if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX))
+ if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX) && toggle_ier)
serial8250_stop_rx(&up->port);
if (up->port.rs485.flags & SER_RS485_RTS_ON_SEND)
@@ -1604,7 +1608,7 @@ static bool start_tx_rs485(struct uart_port *port)
if (em485->tx_stopped) {
em485->tx_stopped = false;
- up->rs485_start_tx(up);
+ up->rs485_start_tx(up, true);
if (up->port.rs485.delay_rts_before_send > 0) {
em485->active_timer = &em485->start_tx_timer;
@@ -3423,7 +3427,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
if (em485) {
if (em485->tx_stopped)
- up->rs485_start_tx(up);
+ up->rs485_start_tx(up, false);
mdelay(port->rs485.delay_rts_before_send);
}
@@ -3461,7 +3465,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
if (em485) {
mdelay(port->rs485.delay_rts_after_send);
if (em485->tx_stopped)
- up->rs485_stop_tx(up);
+ up->rs485_stop_tx(up, false);
}
serial_port_out(port, UART_IER, ier);
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index e0717c8393d7..144de7a7948d 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -161,8 +161,8 @@ struct uart_8250_port {
void (*dl_write)(struct uart_8250_port *up, u32 value);
struct uart_8250_em485 *em485;
- void (*rs485_start_tx)(struct uart_8250_port *);
- void (*rs485_stop_tx)(struct uart_8250_port *);
+ void (*rs485_start_tx)(struct uart_8250_port *up, bool toggle_ier);
+ void (*rs485_stop_tx)(struct uart_8250_port *up, bool toggle_ier);
/* Serial port overrun backoff */
struct delayed_work overrun_backoff;
--
2.39.5
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