linux-kernel - Re: [PATCH] mfd: intel-lpss: Fix Intel Cannon Lake LPSS I2C input clock

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Message-ID: <20180518104638.GF15419@lahna.fi.intel.com>
Date:   Fri, 18 May 2018 13:46:38 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Jarkko Nikula <jarkko.nikula@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-i2c@...r.kernel.org, linux-input@...r.kernel.org,
        Jian-Hong Pan <jian-hong@...lessm.com>,
        Chris Chiu <chiu@...lessm.com>,
        Daniel Drake <drake@...lessm.com>, stable@...r.kernel.org
Subject: Re: [PATCH] mfd: intel-lpss: Fix Intel Cannon Lake LPSS I2C input
 clock

On Fri, May 18, 2018 at 11:38:27AM +0300, Jarkko Nikula wrote:
> Intel Cannon Lake PCH has much higher 216 MHz input clock to LPSS I2C
> than Sunrisepoint which uses 120 MHz. Preliminary information was that
> both share the same clock rate but actual silicon implements elevated
> rate for better support for 3.4 MHz high-speed I2C.
> 
> This incorrect input clock rate results too high I2C bus clock in case
> ACPI doesn't provide tuned I2C timing parameters since I2C host
> controller driver calculates them from input clock rate.
> 
> Fix this by using the correct rate. We still share the same 230 ns SDA
> hold time value than Sunrisepoint.
> 
> Cc: stable@...r.kernel.org
> Fixes: b418bbff36dd ("mfd: intel-lpss: Add Intel Cannonlake PCI IDs")
> Reported-by: Jian-Hong Pan <jian-hong@...lessm.com>
> Reported-by: Chris Chiu <chiu@...lessm.com>
> Reported-by: Daniel Drake <drake@...lessm.com>
> Signed-off-by: Jarkko Nikula <jarkko.nikula@...ux.intel.com>

Acked-by: Mika Westerberg <mika.westerberg@...ux.intel.com>