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There is a period of time between the psmouse deactivate and the ability to communicate with the SMBus companion. Insert a sleep after the deactivate to account for the delay and ensure the SMBus companion is responsive. Attempting to read from the SMBus companion too quickly was causing the touchpad on machines with an i801_smbus companion to stop working after a sleep/resume cycle. On resume the rmi4_smbus would fail with errors reading the SMBus version number: ``` [5454] i2c_i801:i801_check_post:414: i801_smbus 0000:00:1f.3: No response smbus_result: i2c-0 a=02c f=0000 c=fd BYTE_DATA rd res=-6 rmi4_smbus 0-002c: failed to get SMBus version number! ... rmi4_f01 rmi4-00.fn01: Failed to restore normal operation: -6. rmi4_f01 rmi4-00.fn01: Resume failed with code -6. rmi4_physical rmi4-00: Failed to suspend functions: -6 rmi4_smbus 0-002c: Failed to resume device: -6 ``` In this case the rmi_smb_get_version fails with -ENXIO if it happens too soon after the preceding serio_resume -> psmouse_deactivate call. On boot this issue could cause the touchpad to stay in the limited PS/2 mode. This only reproduced in 1 in 10 boots on the Lenovo T440p. Failures in the log on boot would show up as: ``` psmouse serio1: synaptics: Trying to set up SMBus access [122] i2c_i801:i801_check_post:437: i801_smbus 0000:00:1f.3: No response psmouse serio1: synaptics: SMbus companion is not ready yet ``` Experimentation on the Lenovo T440p showed that a delay of 7-12ms on resume allowed the companion to respond. The 30ms delay in this patch was chosen based on the linux-input message: Link: https://lore.kernel.org/all/BYAPR03MB47572F2C65E52ED673238D41B2439@BYAPR03MB4757.namprd03.prod.outlook.com/ Signed-off-by: Jeffery Miller <jefferymiller@google.com> Link: https://lore.kernel.org/r/20230726025256.81174-1-jefferymiller@google.com Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
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.