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Subject: Re: [BUG] i2c-hid: ELAN Touchpad does not work on ASUS X580GD
To: Chris Chiu <chiu@endlessm.com>, Daniel Drake <drake@endlessm.com>
Cc: Jian-Hong Pan <jian-hong@endlessm.com>, Jiri Kosina <jikos@kernel.org>,
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From: Jarkko Nikula <jarkko.nikula@linux.intel.com>
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Date: Mon, 14 May 2018 17:20:22 +0300
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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