linux-kernel - Re: [RESEND] Lenovo Yoga 900 touchpad issues

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Date:	Mon, 21 Dec 2015 13:32:47 +0200
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:	Nish Aravamudan <nish.aravamudan@...il.com>,
	Jiri Kosina <jikos@...nel.org>,
	Andrew Duggan <aduggan@...aptics.com>,
	Gabriele Mazzotta <gabriele.mzt@...il.com>,
	Seth Forshee <seth.forshee@...onical.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	linux-input@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND] Lenovo Yoga 900 touchpad issues

On Fri, Dec 18, 2015 at 05:10:31PM +0100, Benjamin Tissoires wrote:
> After turning this around, I think I finally got what was going on (and
> yes, it's basically a race that should have been caught long ago):
> - during resume, the i2c-hid driver calls reset, which is a long (few
>   ms) operation.
> - hid-multitouch is also called during resume, and right after i2c-hid
> - hid-multiotuch immediately emits for touchpads a set input mode (this
>   was unseen with touchscreens because they do not have to be switched
>   into a proper mode)
> - there is a race between hid-multitouch accessing the features while
>   the device is still resetting. And our reset interrupt never gets to
>   us because there was an other operation in progress to request/set
>   reports
> 
> So the actual fix would be to make hid-multitouch wait until we reset
> i2c-hid.

The driver used for touchpad is actually hid-rmi but you are right, it
tries to set rmi mode (or something) during its rmi_post_reset() that
then confuses the i2c-hid driver.

Thanks for the analysis :-)

> This should be done by either a mutex or a spinlock in
> i2c_hid_output_raw_report() and i2c_hid_resume() that would protect a
> flag set during suspend and cleared after resume.

Makes sense. I'll make a patch that does this and submit it soon.
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