Re: [PATCH 2/2] serial: amba-pl011: keep console clock enabled for atomic writes

[Sebastian Andrzej Siewior]

On 2026-07-19 06:52:14 [+0000], sashiko-bot@xxxxxxxxxx wrote:
> > diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
> > index 1aa43994a3cdc..4facd1b350d5d 100644
> > --- a/drivers/tty/serial/amba-pl011.c
> > +++ b/drivers/tty/serial/amba-pl011.c
> > @@ -2523,7 +2523,11 @@ static int pl011_console_setup(struct console *co, char *options)
> >  	/* Allow pins to be muxed in and configured */
> >  	pinctrl_pm_select_default_state(uap->port.dev);
> >  
> > -	ret = clk_prepare(uap->clk);
> > +	/*
> > +	 * Keep the clock enabled while registered because write_atomic() may
> > +	 * run in NMI context and must not acquire the clock framework lock.
> > +	 */
> > +	ret = clk_prepare_enable(uap->clk);
> 
> [Severity: High]
> Will this keep the UART clock unconditionally enabled during system suspend?
> 
> Because the persistent clock reference is acquired here during console
> registration and only dropped on console exit in pl011_console_exit(), the
> reference remains active.
> 
> During system suspend, pl011_suspend() delegates to uart_suspend_port() but
> fails to drop this console's persistent clock enable reference. This might
> prevent the SoC from turning off the clock tree or parent PLLs, preventing
> deep system sleep.

The comment somehow makes sense. What is the general advice here? If we
drop the clock during suspend and acquire it again during resume we need
to keep track and ignore all prints in between. Is the pritnk core
taking care of this? There is also this no_console_suspend argument…

Sebastian