linux-kernel - [PATCH V3] Set sda-hold-time based on ACPI *CNT value

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Date:   Tue, 28 Mar 2017 16:48:01 +0800
From:   Tan Chin Yew <chin.yew.tan@...el.com>
To:     Wolfram Sang <wsa@...-dreams.de>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH V3] Set sda-hold-time based on ACPI *CNT value

For I2c to operate correctly under all speed mode, sda-hold-time need to
be perfectly tuned. However, sda-hold-time is precalculated according to
circuit parameter which make it platform-specific.

In order to get accurate sda-hold-time for all platforms, pretuned
sda-hold-time for particular platform is stored in ACPI table and driver
to load the sda holding time from ACPI table.

This patch read the I2c sda-hold-time from ACPI table and assigned the
suitable hold time based on the i2c clock frequency.

Tested on Intel Apollo Lake.

Changes in V3:
	- Remove null handling in function dw_i2c_acpi_params.
	- Add descriptions to commit message.

Changes in V2:
	- The code is realigned according to suggestion.
	- "case 400000:" is added on top of "default:" for readability.

Tan Chin Yew (1):
  i2c: designware: Get selected speed mode sda-hold-time via ACPI

 drivers/i2c/busses/i2c-designware-platdrv.c | 31 ++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

-- 
1.9.1