On Tue, Apr 30, 2019 at 05:23:22PM +0300, Jarkko Nikula wrote:
> 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@xxxxxxxxxxxxxx>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=203297
> Fixes: c5eb1190074c ("PCI / PM: Allow runtime PM without callback functions")
> Cc: stable@xxxxxxxxxxxxxxx # v4.20+
> Signed-off-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
Applied to for-current-fixed, thanks!
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