[v1] serial: 8250_port: Update runtime PM flow

[PATCH v1 0/2] serial: 8250_port: Update runtime PM flow

Posted by Andy Shevchenko 1 month, 2 weeks ago

There are two changes, one is a straightforward drop of the duplicate
runtime PM call (which is idempotent and hence it's harmless to call,
but practically no need to do so) and the other addresses long standing
problem with potentially sleeping PM calls on some system in IRQ context.
Also the latter might lead to unneeded resume-suspend cycle when IRQ is
shared and interrupt is not ours. This mini-series to update runtime
PM flow to make sure this won't happen.

Andy Shevchenko (2):
  serial: 8250_port: Remove redundant pm_runtime_mark_last_busy() call
  serial: 8250_port: properly handle runtime PM in IRQ

 drivers/tty/serial/8250/8250_port.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

-- 
2.50.1

Re: [PATCH v1 0/2] serial: 8250_port: Update runtime PM flow

Posted by Greg Kroah-Hartman 5 days, 11 hours ago

On Fri, Aug 14, 2026 at 01:16:28PM +0200, Andy Shevchenko wrote:
> There are two changes, one is a straightforward drop of the duplicate
> runtime PM call (which is idempotent and hence it's harmless to call,
> but practically no need to do so) and the other addresses long standing
> problem with potentially sleeping PM calls on some system in IRQ context.
> Also the latter might lead to unneeded resume-suspend cycle when IRQ is
> shared and interrupt is not ours. This mini-series to update runtime
> PM flow to make sure this won't happen.
> 
> Andy Shevchenko (2):
>   serial: 8250_port: Remove redundant pm_runtime_mark_last_busy() call
>   serial: 8250_port: properly handle runtime PM in IRQ
> 
>  drivers/tty/serial/8250/8250_port.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> -- 
> 2.50.1
> 
> 

  CC      drivers/tty/serial/8250/8250_port.o
drivers/tty/serial/8250/8250_port.c: In function ‘serial8250_default_handle_irq’:
drivers/tty/serial/8250/8250_port.c:1897:32: error: unused variable ‘up’ [-Werror=unused-variable]
 1897 |         struct uart_8250_port *up = up_to_u8250p(port);
      |                                ^~
cc1: all warnings being treated as errors

:(

Re: [PATCH v1 0/2] serial: 8250_port: Update runtime PM flow

Posted by Andy Shevchenko 4 days, 11 hours ago

On Wed, Sep 23, 2026 at 02:41:23PM +0200, Greg Kroah-Hartman wrote:
> On Fri, Aug 14, 2026 at 01:16:28PM +0200, Andy Shevchenko wrote:
> > There are two changes, one is a straightforward drop of the duplicate
> > runtime PM call (which is idempotent and hence it's harmless to call,
> > but practically no need to do so) and the other addresses long standing
> > problem with potentially sleeping PM calls on some system in IRQ context.
> > Also the latter might lead to unneeded resume-suspend cycle when IRQ is
> > shared and interrupt is not ours. This mini-series to update runtime
> > PM flow to make sure this won't happen.

...

>   CC      drivers/tty/serial/8250/8250_port.o
> drivers/tty/serial/8250/8250_port.c: In function ‘serial8250_default_handle_irq’:
> drivers/tty/serial/8250/8250_port.c:1897:32: error: unused variable ‘up’ [-Werror=unused-variable]
>  1897 |         struct uart_8250_port *up = up_to_u8250p(port);
>       |                                ^~
> cc1: all warnings being treated as errors
> 
> :(

Ouch, rebase issue I believe. Thanks for catching this, I will fix in v2!

-- 
With Best Regards,
Andy Shevchenko