On Wed, 29 Jun 2022, Tony Lindgren wrote: > * Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> [220628 21:09]: > > On Tue, Jun 28, 2022 at 07:58:34PM +0300, Ilpo Järvinen wrote: > > > When console is enabled, univ8250_console_setup() calls > > > serial8250_console_setup() before .dev is set to uart_port. Therefore, > > > it will not call pm_runtime_get_sync(). Later, when the actual driver > > > is going to take over univ8250_console_exit() is called. As .dev is > > > already set, serial8250_console_exit() makes pm_runtime_put_sync() call > > > with usage count being zero triggering PM usage count warning > > > (extra debug for univ8250_console_setup(), univ8250_console_exit(), and > > > serial8250_register_ports()): > > Hmm so serial8250_console_setup() calls pm_runtime_get_sync() if dev > exists.. > > > > diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c > > > index 57e86133af4f..2e83e7367441 100644 > > > --- a/drivers/tty/serial/8250/8250_core.c > > > +++ b/drivers/tty/serial/8250/8250_core.c > > > @@ -23,6 +23,7 @@ > > > #include <linux/sysrq.h> > > > #include <linux/delay.h> > > > #include <linux/platform_device.h> > > > +#include <linux/pm_runtime.h> > > > #include <linux/tty.h> > > > #include <linux/ratelimit.h> > > > #include <linux/tty_flip.h> > > > @@ -558,6 +559,9 @@ serial8250_register_ports(struct uart_driver *drv, struct device *dev) > > > > > > up->port.dev = dev; > > > > > > + if (uart_console_enabled(&up->port)) > > > + pm_runtime_get_sync(up->port.dev); > > > + > > > serial8250_apply_quirks(up); > > > uart_add_one_port(drv, &up->port); > > > } > > ..and now we also call it here. Are there now cases where pm_runtime_get_sync() > gets called twice potentially or does uart_console_enabled() ensure that is > not the case already? The code in serial8250_register_ports() right before that context block is this: if (up->port.dev) continue; If serial8250_console_setup() already saw .dev != NULL, we take that continue and pm_runtime_get_sync() will not get called again here. -- i.
