linux-kernel - Re: [PATCH] i2c: imx: add slave support. v2

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Message-ID: <56D96C22.8030104@dev.rtsoft.ru>
Date:	Fri, 4 Mar 2016 14:06:10 +0300
From:	Maxim Syrchin <syrchin@....rtsoft.ru>
To:	Wolfram Sang <wsa@...-dreams.de>,
	Dmitriy Baranov <dbaranov@....rtsoft.ru>
Cc:	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: imx: add slave support. v2

Hi Wolfram,
I'm now working on creating new driver version. I think I'll be able to 
sent it soon.

04.03.2016 0:35, Wolfram Sang пишет:
>> There are might be race conditions.
> Can you name them
Most of races are fixed already. There were some issues with interrupt 
latencies  - sometimes slave interrupt appears in process of starting 
master xfer.
>> +enum imx_i2c_slave_state {
>> +	I2C_IMX_SLAVE_IDLE,
>> +	I2C_IMX_SLAVE_IRQ,
>> +	I2C_IMX_SLAVE_POLLING
> Highlevel question first: Why do you have polling? Why would anyone not
> want to use interrupts here?
Since imx doesn't generate interrupt on "bus stop" condition we'd had to 
implement polling scheme. Interrupts are used for starting polling and 
for  waking polling loop on new slave request. Without polling we can't 
handle "end-of-packet" event correctly.

In current version states are:

	I2C_IMX_SLAVE_IDLE // default state. slave process is waiting for interrupt
	I2C_IMX_SLAVE_POLLING // slave transfer is in process.
	I2C_IMX_MASTER   // master transfer is in process.