72bfcee11c
Multiple users have reported their Synaptics touchpad has stopped
working between v4.20.1 and v4.20.2 when using SMBus interface.
The culprit for this appeared to be commit c5eb1190074c ("PCI / PM: Allow
runtime PM without callback functions") that fixed the runtime PM for
i2c-i801 SMBus adapter. Those Synaptics touchpad are using i2c-i801
for SMBus communication and testing showed they are able to get back
working by preventing the runtime suspend of adapter.
Normally when i2c-i801 SMBus adapter transmits with the client it resumes
before operation and autosuspends after.
However, if client requires SMBus Host Notify protocol, what those
Synaptics touchpads do, then the host adapter must not go to runtime
suspend since then it cannot process incoming SMBus Host Notify commands
the client may send.
Fix this by keeping I2C/SMBus adapter active in case client requires
Host Notify.
Reported-by: Keijo Vaara <ferdasyn@rocketmail.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=203297
Fixes: c5eb1190074c ("PCI / PM: Allow runtime PM without callback functions")
Cc: stable@vger.kernel.org # v4.20+
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Keijo Vaara <ferdasyn@rocketmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.