linux-kernel - Re: [Bug 203297] Synaptics touchpad TM-3127 functionality broken by PCI runtime power management patch on 4.20.2

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Date:   Mon, 29 Apr 2019 11:45:38 +0200
From:   Jean Delvare <jdelvare@...e.de>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Keijo Vaara <ferdasyn@...ketmail.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-pm@...r.kernel.org, linux-pci@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>, linux-input@...r.kernel.org,
        Wolfram Sang <wsa@...-dreams.de>
Subject: Re: [Bug 203297] Synaptics touchpad TM-3127 functionality broken by
 PCI runtime power management patch on 4.20.2

On Mon, 2019-04-29 at 10:53 +0200, Benjamin Tissoires wrote:
> On Mon, Apr 29, 2019 at 10:38 AM Jarkko Nikula
> <jarkko.nikula@...ux.intel.com> wrote:
> > I got another thought about this. I noticed these input drivers need
> > SMBus Host Notify, maybe that explain the PM dependency? If that's the
> > only dependency then we could prevent the controller suspend if there is
> > a client needing host notify mechanism. IMHO that's less hack than the
> > patch to rmi_smbus.c.
> 
> So currently, AFAIK, only Synaptics (rmi4) and Elantech are using
> SMBus Host Notify.
> So this patch would prevent the same bugs for those 2 vendors, which is good.
> 
> It took me some time to understand why this would be less than a hack.
> And indeed, given that Host Notify relies on the I2C connection to be
> ready for the IRQ, we can not put the controller in suspend like we do
> for others where the IRQ controller is still ready.
> 
> So yes, that could work from me. Not sure what Wolfram and Jean would
> say though.

I would say OK with me, this looks like the cleanest solution to me, so
if testing is positive, let's go with it.

-- 
Jean Delvare
SUSE L3 Support