[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <aB0C05WnKkgslAuT@smile.fi.intel.com>
Date: Thu, 8 May 2025 22:15:31 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Herve Codina <herve.codina@...tlin.com>
Cc: Andrew Lunn <andrew@...n.ch>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Danilo Krummrich <dakr@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Fabio Estevam <festevam@...il.com>,
Michael Turquette <mturquette@...libre.com>,
Stephen Boyd <sboyd@...nel.org>, Andi Shyti <andi.shyti@...nel.org>,
Wolfram Sang <wsa+renesas@...g-engineering.com>,
Peter Rosin <peda@...ntia.se>,
Derek Kiernan <derek.kiernan@....com>,
Dragan Cvetic <dragan.cvetic@....com>,
Arnd Bergmann <arnd@...db.de>, Rob Herring <robh@...nel.org>,
Saravana Kannan <saravanak@...gle.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Mark Brown <broonie@...nel.org>, Len Brown <lenb@...nel.org>,
Daniel Scally <djrscally@...il.com>,
Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
Sakari Ailus <sakari.ailus@...ux.intel.com>,
Wolfram Sang <wsa@...nel.org>,
Geert Uytterhoeven <geert+renesas@...der.be>,
linux-kernel@...r.kernel.org, imx@...ts.linux.dev,
linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
linux-pci@...r.kernel.org, linux-spi@...r.kernel.org,
linux-acpi@...r.kernel.org,
Allan Nielsen <allan.nielsen@...rochip.com>,
Horatiu Vultur <horatiu.vultur@...rochip.com>,
Steen Hegelund <steen.hegelund@...rochip.com>,
Luca Ceresoli <luca.ceresoli@...tlin.com>,
Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v2 16/26] i2c: mux: Create missing devlink between mux
and adapter physical device
On Wed, May 07, 2025 at 09:12:58AM +0200, Herve Codina wrote:
> When removing an i2c controller device handling an i2c bus where an i2c
> mux is connected to, the removal process hangs and is stuck in the
> wait_completion() call done in i2c_del_adapter().
>
> The i2c_del_adapter() tries to removed the i2c adapter related to the
> i2c controller device and the wait_completion() is waiting for the i2c
> adapter device release. This release is performed when the device is no
> more used (i.e. refcount reaches zero).
>
> When an i2c mux is involved in an i2c path, the struct dev topology is
> the following:
> +----------------+ +-------------------+
> | i2c controller | | i2c mux |
> | device | | device |
> | ^ | | |
> | | | | |
> | dev's parent | | |
> | | | | |
> | i2c adapter | | i2c adapter chanX |
> | device <---- dev's parent ------ device |
> | (no driver) | | (no driver) |
> +----------------+ +-------------------+
>
> When an i2c mux device creates an i2c adapter for its downstream
> channel, a reference is taken to its adapter dev's parent. This parent
> is the i2c mux upstream adapter device.
>
> No relationship exists between the i2c mux device itself and the i2c
> controller device (physical device) in order to have the i2c mux device
> calling i2c_del_adapter() to remove its downtream adapters and so,
> release references taken to the upstream adapter.
>
> This consumer/supplier relationship is typically a devlink relationship.
>
> Also, i2c muxes can be chained and so, the upstream adapter can be
> supplied by either an i2c controller device or an other i2c mux device.
>
> In order to get the physical device of the adapter a mux is connected
> to, rely on the newly introduced i2c_adapter_get_physdev() and create
> the missing devlink between the i2c mux device and the physical
> device of the adapter the mux is connected to.
>
> With that done, the i2c mux device is removed before the device
> handling the upstream i2c adapter (i2c controller device or i2c mux
> device). All references are released and the i2c_del_adapter() call
> performed by driver handling the upstream adapter device is not blocking
> anymore.
...
> + /*
> + * There is no relationship set between the mux device and the physical
> + * device handling the parent adapter. Create this missing relationship
> + * in order to remove the i2c mux device (consumer) and so the dowstream
> + * channel adapters before removing the physical device (supplier) which
> + * handles the i2c mux upstream adapter.
> + */
> + parent_physdev = i2c_get_adapter_physdev(parent);
> + dl = device_link_add(muxc->dev, parent_physdev, DL_FLAG_AUTOREMOVE_CONSUMER);
> + if (!dl) {
> + dev_err(muxc->dev, "failed to create device link to %s\n",
> + dev_name(parent_physdev));
> + put_device(parent_physdev);
> + ret = -EINVAL;
> + goto err_free_priv;
> + }
> + put_device(parent_physdev);
Since you are not checking parent_physdev for NULL, the dev_name() can print a
"(null)" string. Is this by design?
--
With Best Regards,
Andy Shevchenko
Powered by blists - more mailing lists