Hi,
On 08. 02. 24, 8:52, Yicong Yang wrote:
From: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
We accidently met the issue that the bash prompt is not shown after the
previous command done and until the next input if there's only one CPU
(In our issue other CPUs are isolated by isolcpus=). Further analysis
shows it's because the port entering runtime suspend even if there's
still pending chars in the buffer and the pending chars will only be
processed in next device resuming. We are using amba-pl011 and the
problematic flow is like below:
...
--- a/drivers/tty/serial/serial_port.c
+++ b/drivers/tty/serial/serial_port.c
@@ -19,8 +19,13 @@
/* Only considers pending TX for now. Caller must take care of locking */
static int __serial_port_busy(struct uart_port *port)
{
- return !uart_tx_stopped(port) &&
- uart_circ_chars_pending(&port->state->xmit);
+ if (uart_tx_stopped(port))
+ return 0;
+
+ if (uart_circ_chars_pending(&port->state->xmit))
+ return -EBUSY;
Why do you do this change at all? If anything, __serial_port_busy()
should be made to return a bool and not to return an error. Look how it
is named -- returning EBUSY is sort of unexpected in my eyes. And if
this needed to be done, it should have been in a separate patch anyway.
And then:
@@ -46,8 +51,33 @@ static int serial_port_runtime_resume(struct device *dev)
return 0;
}
+static int serial_port_runtime_suspend(struct device *dev)
+{
+ struct serial_port_device *port_dev = to_serial_base_port_device(dev);
+ struct uart_port *port;
+ unsigned long flags;
+ int ret;
bool busy;
+
+ port = port_dev->port;
+
+ if (port->flags & UPF_DEAD)
+ return 0;
+
+ uart_port_lock_irqsave(port, &flags);
+ ret = __serial_port_busy(port);
+ if (ret)
busy = ...
if (busy)
+ port->ops->start_tx(port);
+ uart_port_unlock_irqrestore(port, flags);
+
+ if (ret)
if (busy)
+ pm_runtime_mark_last_busy(dev);
+
+ return ret;
return busy ? -EBUSY : 0;
+}
thanks,
--
js
suse labs
