From mboxrd@z Thu Jan  1 00:00:00 1970
From: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Subject: Re: [PATCH v2 0/2] i2c:dw: Add APM X-Gene ACPI I2C device support
Date: Tue, 15 Dec 2015 08:52:19 -0600
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To: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: linux-arm-kernel@lists.infradead.org, Al Stone <al.stone@linaro.org>, Jeff.Wu@amd.com, jcm@redhat.com, wsa@the-dreams.de, rjw@rjwysocki.net, linux-i2c@vger.kernel.org, linux-acpi@vger.kernel.org, patches@apm.com, "Duran,
 Leo" <leo.duran@amd.com>, Loc Ho <lho@apm.com>, "Hurwitz,
 Sherry" <sherry.hurwitz@amd.com>, Hanjun Guo <hanjun.guo@linaro.org>, Ken.Xue@amd.com, lenb@kernel.org
List-Id: linux-i2c@vger.kernel.org



On 12/15/2015 07:27 AM, Mika Westerberg wrote:
> On Mon, Dec 14, 2015 at 06:53:25PM -0600, Suravee Suthikulanit wrote:
>> >I'm not sure if this has been discussed earlier. But after looking at the
>> >the acpi_apd driver, all we need is just the platform-specific input clock
>> >frequency value used by the drivers/i2c/busses/i2c-designware-core.c:
>> >i2c_dw_init() to calculate the values to program into the DW_IC_SS_SCL_HCNT
>> >and DW_IC_SS_SCL_LCNT registers.
> There is a way to pass *CNT values already from ACPI to the driver -- It
> looks for method called FMCN (or SSCN) and retrieves the values from
> there if found.

Right, I also noticed this afterward. By the way, are FMCN and SSCN 
documented anywhere in the ACPI spec?  I am trying to figure out how to 
update the ACPI table to add this information for the AMD Seattle 
(ARM64) platform, and I will also submit a patch to add the new HID for 
this driver.

> The driver could be modified not to require clock if it already knows
> *CNT values.
>

Sounds good.

Thanks,
Suravee