linux-kernel - Re: [PATCH v6 1/1] serial: core: Start managing serial controllers to enable runtime PM

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Date:   Fri, 10 Mar 2023 08:51:40 +0200
From:   Tony Lindgren <tony@...mide.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Johan Hovold <johan@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-omap@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH v6 1/1] serial: core: Start managing serial controllers
 to enable runtime PM

* Tony Lindgren <tony@...mide.com> [230309 13:07]:
> * Andy Shevchenko <andriy.shevchenko@...el.com> [230309 12:23]:
> > On Thu, Mar 09, 2023 at 10:57:08AM +0200, Tony Lindgren wrote:
> > > +	err = pm_runtime_get(port_dev);
> > 
> > Is not sync API a deliberate choice? Do we need to comment on why is so?
> 
> I don't think it can be sync version.. See where all __uart_start() may
> get called from. The pm_runtime_get() here is needed so the check for
> pm_runtime_active() won't be racy. Maybe we can now leave out the
> "start TX anyways" part though.

To clarify, the reason we no longer need the check for "start TX anyways"
is we now do pm_runtime_get() on the new port_dev. Earlier we tried to do
it on the physical serial port driver dev where runtime PM possibly was
not enabled.

Regards,

Tony