From: Jarkko Nikula <jarkko.nikula@linux.intel.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Zhuo-hao Lee <zhuo-hao.lee@intel.com>,
mika.westerberg@linux.intel.com, wsa@the-dreams.de,
linux-i2c@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1] i2c: designware: save the preset value of DW_IC_SDA_HOLD
Date: Mon, 29 Aug 2016 09:17:26 +0300 [thread overview]
Message-ID: <70696be2-bead-9241-508d-dd1b02181766@linux.intel.com> (raw)
In-Reply-To: <1472387502.4887.321.camel@linux.intel.com>
On 08/28/2016 03:31 PM, Andy Shevchenko wrote:
> On Sat, 2016-08-27 at 15:39 +0800, Zhuo-hao Lee wrote:
>> There are several ways to set the SDA hold time for i2c controller,
>> including: Device Tree, built-in device properties and ACPI. However,
>> if the SDA hold time is not specified by above method, we should
>> read the value, where it is preset by firmware, and save it to
>> sda_hold_time. This is needed because when i2c controller enters
>> runtime suspend, the DW_IC_SDA_HOLD value will be reset to chipset
>> default value. And during runtime resume, i2c_dw_init will be called
>> to reconfigure i2c controller. If sda_hold_time is zero, the chipset
>> default hold time will be used, that will be too short for some
>> platforms. Therefore, to have a better tolerance, the DW_IC_SDA_HOLD
>> value should be kept by sda_hold_time.
>
> Looks good to me.
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
next prev parent reply other threads:[~2016-08-29 6:17 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-27 7:39 [PATCH v1] i2c: designware: save the preset value of DW_IC_SDA_HOLD Zhuo-hao Lee
2016-08-28 12:31 ` Andy Shevchenko
2016-08-29 6:17 ` Jarkko Nikula [this message]
2016-08-30 20:59 ` Wolfram Sang
2016-08-31 0:24 ` Lee, Zhuo-hao
2016-09-08 20:18 ` Wolfram Sang
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