linux-kernel - Re: [BUG] i2c-hid: ELAN Touchpad does not work on ASUS X580GD

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Message-ID: <c1343704-6b1a-14b5-3942-a8a33f73feee@linux.intel.com>
Date:   Mon, 14 May 2018 17:20:22 +0300
From:   Jarkko Nikula <jarkko.nikula@...ux.intel.com>
To:     Chris Chiu <chiu@...lessm.com>, Daniel Drake <drake@...lessm.com>
Cc:     Jian-Hong Pan <jian-hong@...lessm.com>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Jani Nikula <jani.nikula@...el.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Adrian Salido <salidoa@...gle.com>,
        Jason Gerecke <killertofu@...il.com>,
        linux-input <linux-input@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Linux Upstreaming Team <linux@...lessm.com>
Subject: Re: [BUG] i2c-hid: ELAN Touchpad does not work on ASUS X580GD

On 05/10/2018 03:03 PM, Chris Chiu wrote:
> Report from guys who can access scope. If i2c-sda-falling-time-ns=400ns
> , HCNT increase to 117, the SCL high duration is 576ns as follows
> https://pasteboard.co/HkwERvP.png
> 
> The original SCL high duration (HCNT = 105, 120MHz) is as follows
> https://pasteboard.co/HkwFxgY.png
> 
> So the HCNT does affect but per this HCNT/LCNT value, just not 400kHz
> as expected. Any suggestion?
> 
Thanks for measurements. I was sidetracked last week so I don't have yet 
explanation why signals run faster than expected :-(

Using 120 MHz SPT I2C clocks in commit b418bbff36dd ("mfd: intel-lpss: 
Add Intel Cannonlake PCI IDs") is clearly wrong but before going to 133 
MHz (which work for you but still runs too fast) I would like to find 
explanation why it appears to be much higher.

-- 
Jarkko