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Subject: Re: [BUG] i2c-hid: ELAN Touchpad does not work on ASUS X580GD
From:   Jarkko Nikula <jarkko.nikula@linux.intel.com>
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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Date:   Thu, 17 May 2018 10:48:14 +0300
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Hi

On 05/15/2018 01:20 PM, Jarkko Nikula wrote:
> 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.
> 
I got confirmation that input clock is actually even higher 216 Mhz.

While checking does it cover all of those CNL CNL-LP and CNL-H PCI IDs 
may I add your Jian-Hong, Chris and Daniel email addresses to Repored-by 
tags in a fix patch?

-- 
Jarkko