Hi
After switching to Linux 6.6-rc1, i met an issue during suspend to idle
with 8250_omap driver (no_console_suspend is set).
The driver fails to suspend the uart port used for the serial console so
the suspend sequence is stopped.
[ 114.629197] port 2800000.serial:0.0: PM: calling
pm_runtime_force_suspend+0x0/0x134 @ 114, parent: 2800000.serial:0
[ 114.639617] port 2800000.serial:0.0: PM:
pm_runtime_force_suspend+0x0/0x134 returned 0 after 2 usecs
[ 114.648739] omap8250 2800000.serial: PM: calling
omap8250_suspend+0x0/0xf4 @ 114, parent: bus@100000
[ 114.657861] omap8250 2800000.serial: PM: dpm_run_callback():
omap8250_suspend+0x0/0xf4 returns -16
[ 114.666808] omap8250 2800000.serial: PM: omap8250_suspend+0x0/0xf4
returned -16 after 8951 usecs
[ 114.675580] omap8250 2800000.serial: PM: failed to suspend: error -16
[ 114.682011] PM: suspend of devices aborted after 675.644 msecs
[ 114.687833] PM: start suspend of devices aborted after 681.777 msecs
[ 114.694175] PM: Some devices failed to suspend, or early wake event
detected
The following sequence is used to suspend to idle:
$ echo 1 > /sys/power/pm_debug_messages
$ echo 1 > /sys/power/pm_print_times
$ echo 8 > /proc/sys/kernel/printk
$ echo 0 > /sys/module/printk/parameters/console_suspend
$ echo enabled >
/sys/devices/platform/bus@100000/2800000.serial/tty/ttyS2/power/wakeup
$ echo s2idle > /sys/power/mem_sleep
$ echo mem > /sys/power/state
The regression was introduced in commit 20a41a62618d "serial: 8250_omap:
Use force_suspend and resume for system suspend"
Before commit 20a41a62618d, omap8250_suspend returned 0.
Now pm_runtime_force_suspend is called and its return code is used by
omap8250_suspend.
static int omap8250_suspend(struct device *dev)
{
struct omap8250_priv *priv = dev_get_drvdata(dev);
struct uart_8250_port *up = serial8250_get_port(priv->line);
int err;
serial8250_suspend_port(priv->line);
err = pm_runtime_resume_and_get(dev);
if (err)
return err;
if (!device_may_wakeup(dev))
priv->wer = 0;
serial_out(up, UART_OMAP_WER, priv->wer);
err = pm_runtime_force_suspend(dev);
flush_work(&priv->qos_work);
return err;
}
The pm_runtime_force_suspend function calls omap8250_runtime_suspend
which returns -EBUSY because console suspend was disabled (which is my
case), as explained in the code.
/*
* When using 'no_console_suspend', the console UART must not be
* suspended. Since driver suspend is managed by runtime suspend,
* preventing runtime suspend (by returning error) will keep device
* active during suspend.
*/
if (priv->is_suspending && !console_suspend_enabled) {
if (up && uart_console(&up->port))
return -EBUSY;
}
The port is used by the console, so we don't want to suspend it (console
suspend was disabled).
Of course, if console_suspend is enabled and messages are disabled there
is no issue.
Best Regards,
