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Date:   Mon, 7 Feb 2022 18:20:18 -0800
From:   Dmitry Torokhov <dmitry.torokhov@gmail.com>
To:     Rajat Jain <rajatja@google.com>
Cc:     Wolfram Sang <wsa@kernel.org>, Hugh Dickins <hughd@google.com>,
        Derek Basehore <dbasehore@chromium.org>,
        Jarkko Nikula <jarkko.nikula@linux.intel.com>,
        Thorsten Leemhuis <regressions@leemhuis.info>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-i2c <linux-i2c@vger.kernel.org>,
        "loic.poulain@linaro.org" <loic.poulain@linaro.org>,
        Andrew Duggan <aduggan@synaptics.com>,
        vincent.huang@tw.synaptics.com, cheiny@synaptics.com,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        linux-input <linux-input@vger.kernel.org>
Subject: Re: 5.17-rc regression: rmi4 clients cannot deal with asynchronous
 suspend? (was: X1 Carbon touchpad not resumed)
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On Mon, Feb 07, 2022 at 01:41:36PM -0800, Rajat Jain wrote:
> +linux-input@vger.kernel.org
> 
> On Mon, Feb 7, 2022 at 1:09 PM Rajat Jain <rajatja@google.com> wrote:
> >
> > +Rafael (for any inputs on asynchronous suspend / resume)
> > +Dmitry Torokhov (since no other maintainer of rmi4 in MAINTAINERS file)
> > +loic.poulain@linaro.org (who fixed RMI device hierarchy recently)
> > + Some Synaptics folks (from recent commits - Vincent Huang, Andrew
> > Duggan, Cheiny)
> >
> > On Mon, Feb 7, 2022 at 12:23 PM Wolfram Sang <wsa@kernel.org> wrote:
> > >
> > > Hello Hugh,
> > >
> > > > Bisection led to 172d931910e1db800f4e71e8ed92281b6f8c6ee2
> > > > ("i2c: enable async suspend/resume on i2c client devices")
> > > > and reverting that fixes it for me.
> > >
> > > Thank you for the report plus bisection and sorry for the regression!
> >
> > +1, Thanks for the bisection, and apologies for the inconveniences.
> >
> > The problem here seems to be that for some reason, some devices (all
> > connected to rmi4 adapter) failed to resume, but only when
> > asynchronous suspend is enabled (by 172d931910e1):
> >
> > [   79.221064] rmi4_smbus 6-002c: failed to get SMBus version number!
> > [   79.265074] rmi4_physical rmi4-00: rmi_driver_reset_handler: Failed
> > to read current IRQ mask.
> > [   79.308330] rmi4_f01 rmi4-00.fn01: Failed to restore normal operation: -6.
> > [   79.308335] rmi4_f01 rmi4-00.fn01: Resume failed with code -6.
> > [   79.308339] rmi4_physical rmi4-00: Failed to suspend functions: -6
> > [   79.308342] rmi4_smbus 6-002c: Failed to resume device: -6
> > [   79.351967] rmi4_physical rmi4-00: Failed to read irqs, code=-6
> >
> > A resume failure that only shows up during asynchronous resume,
> > typically means that the device is dependent on some other device to
> > resume first, but this dependency is NOT established in a parent child
> > relationship (which is wrong and needs to be fixed, perhaps using
> > device_add_link()). Thus the kernel may be resuming these devices
> > without first resuming some other device that these devices need to
> > depend on.
> >
> > TBH, I'm not sure how to fix this. The only hint I see is that all of
> > these devices seem to be attached to rmi4 device so perhaps something
> > there? I see 6e4860410b828f recently fixed device hierarchy for rmi4,
> > and so seemingly should have fixed this very issue (as also seen in
> > commit message)?
> >
> > >
> > > I will wait a few days if people come up with a fix. If not, I will
> > > revert the offending commit.
> >
> > While I'll be sad because this means no i2c-client can now resume in
> > parallel and increases resume latency by a *LOT* (hundreds of ms on
> > all Linux systems), I understand that this needs to be done unless
> > someone comes up with a fix.

There is intricate dance happening switching touchpad from legacy PS/2
into RMI mode, with touchpad being dependent not only on SMbus
controller, but also on i8042 keyboard controller and its PS/2 port (or
rather their emulation by the system firmware).

I wonder if we could apply a little bit more targeted patch:

diff --git a/drivers/input/rmi4/rmi_smbus.c b/drivers/input/rmi4/rmi_smbus.c
index 2407ea43de59..3901d06d38ca 100644
--- a/drivers/input/rmi4/rmi_smbus.c
+++ b/drivers/input/rmi4/rmi_smbus.c
@@ -335,6 +335,7 @@ static int rmi_smb_probe(struct i2c_client *client,
 		return error;
 	}
 
+	device_disable_async_suspend(&client->dev);
 	return 0;
 }
 

... and if that works then we cant try to establish proper dependencies
via device links later.

Hugh, could you please try this out and see if it helps?

Thanks!

-- 
Dmitry