On Fri, 2014-11-14 at 11:12 +0800, xudong chen wrote:

On Thu, 2014-11-13 at 19:31 +0100, Wolfram Sang wrote:

quoted

quoted

MTK I2C HW has some limitation.
1. If the i2c_msg number is more than one, STOP will be issued instead of
RS(Repeat Start) between each message.

2. Mediatek I2C controller support WRRD(write then read) mode, in WRRD
mode the Repeat Start will be issued between 2 messages.
In this driver if 2 messages is first write then read, the driver will
combine 2 messages using Write-Read mode so the RS will be issued between
the 2 messages.
Ex: W/R/R, driver will combine first W/R and then R.

3. Due to HW limitation, in this version the max transfer data length is 255
in one message.

This looks to me more like an SMBUS controller instead of I2C. Maybe you
should populate smbus_xfer rather than master_xfer?

This is the HW limitation, we will try to workaround this in the
separate patch.

Except limited RS and limited length support, our HW follow I2C protocol
spec.
The length is compatible with most I2C devices, only a few I2C devices
need transfer more than 255 bytes.
The future Mediatek IC will fix the RS and length limitation.

Thanks!

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