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 16:31:35 -0800
From:	Loc Ho <lho@....com>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	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 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
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