[PATCH v2 6/6] tty: serial: atmel: rework interrupt and wakeup handling

Boris Brezillon
2015-03-02T09:18:18Z

The IRQ line connected to the DBGU UART is often shared with a timer device
which request the IRQ with IRQF_NO_SUSPEND.
Since the UART driver is correctly disabling IRQs when entering suspend
we can safely request the IRQ with IRQF_COND_SUSPEND so that irq core
will not complain about mixing IRQF_NO_SUSPEND and !IRQF_NO_SUSPEND.

Rework the interrupt handler to wake the system up when an interrupt
happens on the DEBUG_UART while the system is suspended.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
drivers/tty/serial/atmel_serial.c | 49 +++++++++++++++++++++++++++++++++++----
1 file changed, 45 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 846552b..4e959c4 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -47,6 +47,7 @@
#include <linux/gpio/consumer.h>
#include <linux/err.h>
#include <linux/irq.h>
+#include <linux/suspend.h>

#include <asm/io.h>
#include <asm/ioctls.h>
@@ -173,6 +174,12 @@ struct atmel_uart_port {
bool ms_irq_enabled;
bool is_usart; /* usart or uart */
struct timer_list uart_timer; /* uart timer */
+
+ bool suspended;
+ unsigned int pending;
+ unsigned int pending_status;
+ spinlock_t lock_suspended;
+
int (*prepare_rx)(struct uart_port *port);
int (*prepare_tx)(struct uart_port *port);
void (*schedule_rx)(struct uart_port *port);
@@ -1179,12 +1186,15 @@ static irqreturn_t atmel_interrupt(int irq, void *dev_id)
{
struct uart_port *port = dev_id;
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
- unsigned int status, pending, pass_counter = 0;
+ unsigned int status, pending, mask, pass_counter = 0;
bool gpio_handled = false;

+ spin_lock(&atmel_port->lock_suspended);
+
do {
status = atmel_get_lines_status(port);
- pending = status & UART_GET_IMR(port);
+ mask = UART_GET_IMR(port);
+ pending = status & mask;
if (!gpio_handled) {
/*
* Dealing with GPIO interrupt
@@ -1206,11 +1216,21 @@ static irqreturn_t atmel_interrupt(int irq, void *dev_id)
if (!pending)
break;

+ if (atmel_port->suspended) {
+ atmel_port->pending |= pending;
+ atmel_port->pending_status = status;
+ UART_PUT_IDR(port, mask);
+ pm_system_wakeup();
+ break;
+ }
+
atmel_handle_receive(port, pending);
atmel_handle_status(port, pending, status);
atmel_handle_transmit(port, pending);
} while (pass_counter++ < ATMEL_ISR_PASS_LIMIT);

+ spin_unlock(&atmel_port->lock_suspended);
+
return pass_counter ? IRQ_HANDLED : IRQ_NONE;
}

@@ -1742,7 +1762,8 @@ static int atmel_startup(struct uart_port *port)
/*
* Allocate the IRQ
*/
- retval = request_irq(port->irq, atmel_interrupt, IRQF_SHARED,
+ retval = request_irq(port->irq, atmel_interrupt,
+ IRQF_SHARED | IRQF_COND_SUSPEND,
tty ? tty->name : "atmel_serial", port);
if (retval) {
dev_err(port->dev, "atmel_startup - Can't get irq\n");
@@ -2513,8 +2534,14 @@ static int atmel_serial_suspend(struct platform_device *pdev,

/* we can not wake up if we're running on slow clock */
atmel_port->may_wakeup = device_may_wakeup(&pdev->dev);
- if (atmel_serial_clk_will_stop())
+ if (atmel_serial_clk_will_stop()) {
+ unsigned long flags;
+
+ spin_lock_irqsave(&atmel_port->lock_suspended, flags);
+ atmel_port->suspended = true;
+ spin_unlock_irqrestore(&atmel_port->lock_suspended, flags);
device_set_wakeup_enable(&pdev->dev, 0);
+ }

uart_suspend_port(&atmel_uart, port);

@@ -2525,6 +2552,18 @@ static int atmel_serial_resume(struct platform_device *pdev)
{
struct uart_port *port = platform_get_drvdata(pdev);
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+ unsigned long flags;
+
+ spin_lock_irqsave(&atmel_port->lock_suspended, flags);
+ if (atmel_port->pending) {
+ atmel_handle_receive(port, atmel_port->pending);
+ atmel_handle_status(port, atmel_port->pending,
+ atmel_port->pending_status);
+ atmel_handle_transmit(port, atmel_port->pending);
+ atmel_port->pending = 0;
+ }
+ atmel_port->suspended = false;
+ spin_unlock_irqrestore(&atmel_port->lock_suspended, flags);

uart_resume_port(&atmel_uart, port);
device_set_wakeup_enable(&pdev->dev, atmel_port->may_wakeup);
@@ -2593,6 +2632,8 @@ static int atmel_serial_probe(struct platform_device *pdev)
port->backup_imr = 0;
port->uart.line = ret;

+ spin_lock_init(&port->lock_suspended);
+
ret = atmel_init_gpios(port, &pdev->dev);
if (ret < 0)
dev_err(&pdev->dev, "%s",
--
1.9.1