linux-kernel - Re: [PATCH v4] i2c: designware: Do not require clock when SSCN and FFCN are provided

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Date:	Wed, 6 Jan 2016 23:05:14 -0600
From:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To:	Loc Ho <lho@....com>, Wolfram Sang <wsa@...-dreams.de>
CC:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	<jarkko.nikula@...ux.intel.com>,
	<andriy.shevchenko@...ux.intel.com>, Ken Xue <Ken.Xue@....com>,
	<linux-i2c@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] i2c: designware: Do not require clock when SSCN and
 FFCN are provided

Hi,

On 01/06/2016 06:31 PM, Loc Ho wrote:
> Hi All,
>
>>> The current driver uses input clock source frequency to calculate
>>> values for [SS|FS]_[HC|LC] registers. However, when booting ACPI, we do not
>>> currently have a good way to provide the frequency information.
>>> Instead, we can leverage the SSCN and FFCN ACPI methods, which can be used
>>> to directly provide these values. So, the clock information should
>>> no longer be required during probing.
>>>
>>> However, since clk can be invalid, additional checks must be done where
>>> we are making use of it.
>>>
>>> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
>>> Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
>>> Tested-by: Loc Ho <lho@....com>
>>> ---
>>>
>>> Note: This has been tested on AMD Seattle RevB for both DT and ACPI.
>>>
>>> Changes from V3 (https://lkml.org/lkml/2015/12/22/596):
>>>      * Add i2c_dw_plat_prepare_clk() per Andy's suggestion
>>>      * Add tested-by Loc Ho.
>>
>> The changes from V3 are big enough that I'd appreciate a new Tested-by
>> tag.
>
> I had tested this via this mixes of test cases:
>
> a. NO APD driver + this patch ==> HCNT/LCNT as expected
> b. with APD driver + this patch ==> HCNT/LCNT as expected
> c. with APD driver + this patch + double the frequency APD driver ==>
> HCNT/LCNT as expected
> d. with APD driver + this patch + double the frequency APD driver +
> comment out the ACPI parameter retrieve ==> HCNT/LCNT changed as
> expected
>
> Therefore, you can add my - Tested-by: Loc Ho <lho@....com>
>
> -Loc
>

Thanks Loc,

Suravee
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