linux-kernel - [2nd RESEND PATCH 0/2] i2c: enable buses to save their clock frequency in adapter

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Message-ID: <20181207112939.15791-1-tudor.ambarus@microchip.com>
Date:   Fri, 7 Dec 2018 11:29:52 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <wsa@...-dreams.de>
CC:     <Nicolas.Ferre@...rochip.com>, <Ludovic.Desroches@...rochip.com>,
        <alexandre.belloni@...tlin.com>, <linux-i2c@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <Tudor.Ambarus@...rochip.com>
Subject: [2nd RESEND PATCH 0/2] i2c: enable buses to save their clock
 frequency in adapter

From: Tudor Ambarus <tudor.ambarus@...rochip.com>

The clock-frequency property is not mandatory for the i2c buses. If it's
not present in the device tree, the buses __usually__ assume it's 100kHZ
(see altera, at91, axxia, etc.). Broadcom uses a 375kHZ default
clock-frequency, so the default clock frequency varies from bus to bus.

There are i2c clients that need to know the bus clock frequency in order to
compute their wake token (see atecc508a i2c client).

The clock-frequency value has to be propagated to the i2c clients, otherwise,
if they will not find the i2c bus clock frequency in the device tree, they
will have to make their own assumption of the clock frequency.

Spare the i2c clients of making wrong assumptions of the i2c bus clock
frequency and enable the buses to save their clock frequency in adapter.

since rfc:
- reword commit messages

Tudor.Ambarus@...rochip.com (2):
  i2c: enable buses to save their clock frequency in adapter
  i2c: at91: Save the bus clock frequency in adapter

 drivers/i2c/busses/i2c-at91.c | 1 +
 include/linux/i2c.h           | 1 +
 2 files changed, 2 insertions(+)

-- 
2.9.4