sc16is7xx: use kthread_worker for tx_work and irq
Convert workqueue usage to a real-time kworker. The problem
with workqueues is that we cannot set real-time priorities on
our work and asynchronous reconfiguration can be blocked by
less important tasks.
We need kthread for the interrupt anyway and because we will
now be using single kthread for all TX-related operations we
can get rid of the port mutex.
Signed-off-by: Jakub Kicinski <kubakici@wp.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index ea61a29..e6553d0 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -303,7 +303,7 @@
struct sc16is7xx_one {
struct uart_port port;
- struct work_struct tx_work;
+ struct kthread_work tx_work;
struct work_struct md_work;
};
@@ -311,15 +311,18 @@
struct uart_driver uart;
struct sc16is7xx_devtype *devtype;
struct regmap *regmap;
- struct mutex mutex;
struct clk *clk;
#ifdef CONFIG_GPIOLIB
struct gpio_chip gpio;
#endif
unsigned char buf[SC16IS7XX_FIFO_SIZE];
+ struct kthread_worker kworker;
+ struct task_struct *kworker_task;
+ struct kthread_work irq_work;
struct sc16is7xx_one p[0];
};
+#define to_sc16is7xx_port(p,e) ((container_of((p), struct sc16is7xx_port, e)))
#define to_sc16is7xx_one(p,e) ((container_of((p), struct sc16is7xx_one, e)))
static u8 sc16is7xx_port_read(struct uart_port *port, u8 reg)
@@ -616,9 +619,7 @@
!!(msr & SC16IS7XX_MSR_CTS_BIT));
break;
case SC16IS7XX_IIR_THRI_SRC:
- mutex_lock(&s->mutex);
sc16is7xx_handle_tx(port);
- mutex_unlock(&s->mutex);
break;
default:
dev_err_ratelimited(port->dev,
@@ -629,25 +630,29 @@
} while (1);
}
-static irqreturn_t sc16is7xx_ist(int irq, void *dev_id)
+static void sc16is7xx_ist(struct kthread_work *ws)
{
- struct sc16is7xx_port *s = (struct sc16is7xx_port *)dev_id;
+ struct sc16is7xx_port *s = to_sc16is7xx_port(ws, irq_work);
int i;
for (i = 0; i < s->uart.nr; ++i)
sc16is7xx_port_irq(s, i);
+}
+
+static irqreturn_t sc16is7xx_irq(int irq, void *dev_id)
+{
+ struct sc16is7xx_port *s = (struct sc16is7xx_port *)dev_id;
+
+ queue_kthread_work(&s->kworker, &s->irq_work);
return IRQ_HANDLED;
}
-static void sc16is7xx_wq_proc(struct work_struct *ws)
+static void sc16is7xx_tx_proc(struct kthread_work *ws)
{
struct sc16is7xx_one *one = to_sc16is7xx_one(ws, tx_work);
- struct sc16is7xx_port *s = dev_get_drvdata(one->port.dev);
- mutex_lock(&s->mutex);
sc16is7xx_handle_tx(&one->port);
- mutex_unlock(&s->mutex);
}
static void sc16is7xx_stop_tx(struct uart_port* port)
@@ -669,6 +674,7 @@
static void sc16is7xx_start_tx(struct uart_port *port)
{
+ struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
/* handle rs485 */
@@ -677,8 +683,7 @@
mdelay(port->rs485.delay_rts_before_send);
}
- if (!work_pending(&one->tx_work))
- schedule_work(&one->tx_work);
+ queue_kthread_work(&s->kworker, &one->tx_work);
}
static unsigned int sc16is7xx_tx_empty(struct uart_port *port)
@@ -909,6 +914,8 @@
static void sc16is7xx_shutdown(struct uart_port *port)
{
+ struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
+
/* Disable all interrupts */
sc16is7xx_port_write(port, SC16IS7XX_IER_REG, 0);
/* Disable TX/RX */
@@ -919,6 +926,8 @@
SC16IS7XX_EFCR_TXDISABLE_BIT);
sc16is7xx_power(port, 0);
+
+ flush_kthread_worker(&s->kworker);
}
static const char *sc16is7xx_type(struct uart_port *port)
@@ -1036,6 +1045,7 @@
struct sc16is7xx_devtype *devtype,
struct regmap *regmap, int irq, unsigned long flags)
{
+ struct sched_param sched_param = { .sched_priority = MAX_RT_PRIO / 2 };
unsigned long freq, *pfreq = dev_get_platdata(dev);
int i, ret;
struct sc16is7xx_port *s;
@@ -1077,6 +1087,16 @@
goto out_clk;
}
+ init_kthread_worker(&s->kworker);
+ init_kthread_work(&s->irq_work, sc16is7xx_ist);
+ s->kworker_task = kthread_run(kthread_worker_fn, &s->kworker,
+ "sc16is7xx");
+ if (IS_ERR(s->kworker_task)) {
+ ret = PTR_ERR(s->kworker_task);
+ goto out_uart;
+ }
+ sched_setscheduler(s->kworker_task, SCHED_FIFO, &sched_param);
+
#ifdef CONFIG_GPIOLIB
if (devtype->nr_gpio) {
/* Setup GPIO cotroller */
@@ -1092,12 +1112,10 @@
s->gpio.can_sleep = 1;
ret = gpiochip_add(&s->gpio);
if (ret)
- goto out_uart;
+ goto out_thread;
}
#endif
- mutex_init(&s->mutex);
-
for (i = 0; i < devtype->nr_uart; ++i) {
/* Initialize port data */
s->p[i].port.line = i;
@@ -1117,7 +1135,7 @@
SC16IS7XX_EFCR_RXDISABLE_BIT |
SC16IS7XX_EFCR_TXDISABLE_BIT);
/* Initialize queue for start TX */
- INIT_WORK(&s->p[i].tx_work, sc16is7xx_wq_proc);
+ init_kthread_work(&s->p[i].tx_work, sc16is7xx_tx_proc);
/* Initialize queue for changing mode */
INIT_WORK(&s->p[i].md_work, sc16is7xx_md_proc);
/* Register port */
@@ -1127,22 +1145,23 @@
}
/* Setup interrupt */
- ret = devm_request_threaded_irq(dev, irq, NULL, sc16is7xx_ist,
- IRQF_ONESHOT | flags, dev_name(dev), s);
+ ret = devm_request_irq(dev, irq, sc16is7xx_irq,
+ IRQF_ONESHOT | flags, dev_name(dev), s);
if (!ret)
return 0;
for (i = 0; i < s->uart.nr; i++)
uart_remove_one_port(&s->uart, &s->p[i].port);
- mutex_destroy(&s->mutex);
-
#ifdef CONFIG_GPIOLIB
if (devtype->nr_gpio)
gpiochip_remove(&s->gpio);
-out_uart:
+out_thread:
#endif
+ kthread_stop(s->kworker_task);
+
+out_uart:
uart_unregister_driver(&s->uart);
out_clk:
@@ -1163,13 +1182,14 @@
#endif
for (i = 0; i < s->uart.nr; i++) {
- cancel_work_sync(&s->p[i].tx_work);
cancel_work_sync(&s->p[i].md_work);
uart_remove_one_port(&s->uart, &s->p[i].port);
sc16is7xx_power(&s->p[i].port, 0);
}
- mutex_destroy(&s->mutex);
+ flush_kthread_worker(&s->kworker);
+ kthread_stop(s->kworker_task);
+
uart_unregister_driver(&s->uart);
if (!IS_ERR(s->clk))
clk_disable_unprepare(s->clk);