From: Tony Lindgren <tony@atomide.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Jiri Slaby" <jirislaby@kernel.org>,
"Andy Shevchenko" <andriy.shevchenko@intel.com>,
"Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>,
"Johan Hovold" <johan@kernel.org>,
"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>,
"Vignesh Raghavendra" <vigneshr@ti.com>,
linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-serial@vger.kernel.org
Subject: Re: [PATCH v5 1/1] serial: core: Start managing serial controllers to enable runtime PM
Date: Wed, 1 Feb 2023 08:38:42 +0200 [thread overview]
Message-ID: <Y9oI8m132aQOeSed@atomide.com> (raw)
In-Reply-To: <Y9jo9bTnmejWYoH2@kroah.com>
* Greg Kroah-Hartman <gregkh@linuxfoundation.org> [230131 10:10]:
> 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.
>
> Looking better, but why is this new device a platform device? That
> feels odd, you should never have a platform device hanging off of a
> non-platform device, right?
No special need for it to be a platform device. It just is easy to set
up, and for my test case the serial port physical device is also a
platform device.
What's your preference here?
> What does the sysfs tree look like now with this patch applied?
Below are two examples of what's in sysfs.
Regards,
Tony
8< -----------------
On arm64 with two physical 8250 devices I have:
# ls -l /sys/devices/platform/serial8250/
total 0
lrwxrwxrwx 1 root root 0 Jan 1 1970 driver -> ../../../bus/platform/drivers/serial8250
-rw-r--r-- 1 root root 4096 Jan 1 1970 driver_override
-r--r--r-- 1 root root 4096 Jan 1 1970 modalias
drwxr-xr-x 2 root root 0 Jan 1 1970 power
drwxr-xr-x 5 root root 0 Jan 1 1970 serial-ctrl.0.auto
lrwxrwxrwx 1 root root 0 Jan 1 1970 subsystem -> ../../../bus/platform
drwxr-xr-x 4 root root 0 Jan 1 1970 tty
-rw-r--r-- 1 root root 4096 Jan 1 1970 uevent
# ls -l /sys/devices/platform/serial8250/serial-ctrl*
total 0
lrwxrwxrwx 1 root root 0 Jan 1 1970 driver -> ../../../../bus/platform/drivers/serial-ctrl
-rw-r--r-- 1 root root 4096 Jan 1 1970 driver_override
-r--r--r-- 1 root root 4096 Jan 1 1970 modalias
drwxr-xr-x 2 root root 0 Jan 1 1970 power
drwxr-xr-x 3 root root 0 Jan 1 1970 serial-port.1.auto
drwxr-xr-x 3 root root 0 Jan 1 1970 serial-port.4.auto
lrwxrwxrwx 1 root root 0 Jan 1 1970 subsystem -> ../../../../bus/platform
-rw-r--r-- 1 root root 4096 Jan 1 1970 uevent
On x86_64 qemu with one port I have:
# ls -l /sys/devices/pnp0/00:04/
total 0
lrwxrwxrwx 1 root root 0 Feb 1 06:13 driver -> ../../../bus/pnp/drivers/serial
lrwxrwxrwx 1 root root 0 Feb 1 06:13 firmware_node -> ../../LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:01/PNP0501:00
-r--r--r-- 1 root root 4096 Feb 1 06:13 id
-r--r--r-- 1 root root 4096 Feb 1 06:13 options
-rw-r--r-- 1 root root 4096 Feb 1 06:13 resources
drwxr-xr-x 3 root root 0 Feb 1 06:12 serial-ctrl.0.auto
lrwxrwxrwx 1 root root 0 Feb 1 06:13 subsystem -> ../../../bus/pnp
drwxr-xr-x 3 root root 0 Feb 1 06:12 tty
-rw-r--r-- 1 root root 4096 Feb 1 06:12 uevent
# ls -l /sys/devices/pnp0/00:04/serial-ctrl.0.auto/
total 0
lrwxrwxrwx 1 root root 0 Feb 1 06:13 driver -> ../../../../bus/platform/drivers/serial-ctrl
-rw-r--r-- 1 root root 4096 Feb 1 06:13 driver_override
-r--r--r-- 1 root root 4096 Feb 1 06:13 modalias
drwxr-xr-x 2 root root 0 Feb 1 06:12 serial-port.1.auto
lrwxrwxrwx 1 root root 0 Feb 1 06:13 subsystem -> ../../../../bus/platform
-rw-r--r-- 1 root root 4096 Feb 1 06:12 uevent
next prev parent reply other threads:[~2023-02-01 6:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-16 7:59 [PATCH v5 1/1] serial: core: Start managing serial controllers to enable runtime PM Tony Lindgren
2023-01-31 10:09 ` Greg Kroah-Hartman
2023-02-01 6:38 ` Tony Lindgren [this message]
2023-04-20 11:34 ` Greg Kroah-Hartman
2023-03-02 16:06 ` Andy Shevchenko
2023-03-06 6:49 ` Tony Lindgren
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