From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Subject: Re: [BUG] i2c-hid: ELAN Touchpad does not work on ASUS X580GD
Date: Tue, 15 May 2018 13:20:58 +0300
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To: Chris Chiu <chiu@endlessm.com>
Cc: Daniel Drake <drake@endlessm.com>, Jian-Hong Pan <jian-hong@endlessm.com>, Jiri Kosina <jikos@kernel.org>, Benjamin Tissoires <benjamin.tissoires@redhat.com>, Jani Nikula <jani.nikula@intel.com>, Hans de Goede <hdegoede@redhat.com>, Dmitry Torokhov <dmitry.torokhov@gmail.com>, Adrian Salido <salidoa@google.com>, Jason Gerecke <killertofu@gmail.com>, linux-input <linux-input@vger.kernel.org>, Andy Shevchenko <andriy.shevchenko@linux.intel.com>, Mika Westerberg <mika.westerberg@linux.intel.com>, Wolfram Sang <wsa@the-dreams.de>, linux-i2c@vger.kernel.org, Linux Kernel <linux-kernel@vger.kernel.org>, Linux Upstreaming Team <linux@endlessm.com>
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On 05/15/2018 06:22 AM, Chris Chiu wrote:
> What if I change the 120MHz to 180MHz and then make sure that the I2C operates
> in target FS mode frequency 400kHz via scope? Would there be any side effect?
> Maybe some other busses frequency could be also affected and causing some other
> component malfunction?
> 
Should be safe. It is only clock rate information when registering a 
fixed clock with known rate in intel-lpss.c and i2c-designware uses that 
info when calculating the timing parameters. I.e. it doesn't change any 
internal clocks.

I'm trying to find a contact who can confirm what is the expected rate 
of I2C input clock and is it common to all Cannon Lake HW.

-- 
Jarkko