linux-kernel - Re: [PATCH v5 1/1] serial: core: Start managing serial controllers to enable runtime PM

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Date:   Mon, 6 Mar 2023 08:49:27 +0200
From:   Tony Lindgren <tony@...mide.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>
Cc:     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-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH v5 1/1] serial: core: Start managing serial controllers
 to enable runtime PM

* Andy Shevchenko <andriy.shevchenko@...el.com> [230302 16:07]:
> On Mon, Jan 16, 2023 at 09:59:58AM +0200, Tony Lindgren wrote:
> > We want to enable runtime PM for serial port device drivers in a generic
> > way. To do this, we want to have the serial core layer manage the
> > registered physical serial controller devices.
> > 
> > To do this, let's set up a struct device for the serial core controller
> > as suggested by Greg and Jiri. The serial core controller devices are
> > children of the physical serial port device. The serial core controller
> > device is needed to support multiple different kind of ports connected
> > to single physical serial port device.
> > 
> > Let's also set up a struct device for the serial core port. The serial
> > core port instances are children of the serial core controller device.
> > 
> > With the serial core port device we can now flush pending TX on the
> > runtime PM resume as suggested by Johan.
> 
> A side note. Perhaps it makes sense to also clean up documentation somehow
> related to this change. For example, I found that
> Documentation/firmware-guide/acpi/enumeration.rst has this:
> 
>   "Note that standard UARTs are not busses so there is no struct uart_device,
>    although some of them may be represented by struct serdev_device."

OK good point, will update that for the next version.

FYI, I replaced the serial core platform bus with just struct device and
bus, need to clean-up a bit before posting though.

Regards,

Tony