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

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Message-ID: <0f7d5f1c-5889-27f3-f4e0-fc79960b8bf2@mentor.com>
Date:   Mon, 31 Oct 2016 11:14:08 +0900
From:   "Frkuska, Joshua" <joshua_frkuska@...tor.com>
To:     Maxim Syrchin <syrchin@....rtsoft.ru>, <linux-i2c@...r.kernel.org>
CC:     <wsa@...-dreams.de>, <peda@...ntia.se>, <Jiada_Wang@...tor.com>,
        <linux-kernel@...r.kernel.org>,
        "Zapolskiy, Vladimir" <vladimir_zapolskiy@...tor.com>,
        "Baxter, Jim" <Jim_Baxter@...tor.com>
Subject: Re: [PATCH] i2c: imx: add slave support. v2 status

Hello Maxim,

Thank you very much for the intermediate patch. I am in the process of 
reviewing it. Please let me clarify a few questions I have.

1. What alternative to "bus busy/bus free/IBB" polling do you have in 
mind? This seems like a reasonable approach to me.
2. What are the major points you consider in need of refactoring?
3. You mention race conditions being fixed in this version relating to 
bus-locking by the slave and breaking slave transactions by the master. 
Does this mean mixed slave/master mode works to your satisfaction? If 
not, what work still needs to be done here?
4. You mention the need for a slave locking test and a work-around 
(checking IMX_I2C_I2DR and IBB) being in-place. Why is this work-around 
not sufficient?

Thanks again,

Joshua

On 10/28/2016 04:38 AM, Maxim Syrchin wrote:
> Hi,
> Sorry for huge delay in answering. Unfortunately we don't have enough 
> resources now to prepare clean enough patch to be accepted by community.
> Please find the latest version attached.  Driver has passed stress 
> tests, but looks like it need seriuos refactoring (it is unnecessarily 
> complicated).
> We still have polling in slave code. Since imx doesn't generate 
> interrupt on "bus busy"/"bus free" events we have to test IBB bit in 
> polling loop.
> Comparing to v2 version several race conditions were fixed (bus 
> locking by slave, breaking slave transaction by starting master xfer). 
> v2 is working pretty good in slave-only or master-only mode. It is 
> reasonable to add  slave locking test  - sometimes imx6 hw doesn't 
> release data line. As workaround we use dummy reading of IMX_I2C_I2DR 
> if driver is in  slave mode and IBB bit is set for a long time.
>
> Thanks,
> Maxim Syrchin
>
>
> 27.10.2016 10:31, Frkuska, Joshua пишет:
>> Hi Maxim, Dmitriy, Wolfram,
>>
>> If there is no immediate plan for a third release of the below patch 
>> set, would it be possible to continue with merging v2 after 
>> addressing the remaining concerns?
>>
>>
>> Thank you and regards,
>>
>> Joshua
>>> Hi Maxim,
>>>
>>> On 2016-03-04 11:06:10 in the thread "Re: [PATCH] i2c: imx: add 
>>> slave support. v2"
>>> referenced here:   https://patchwork.ozlabs.org/patch/573353/ you said:
>>>> Hi Wolfram,
>>>> I'm now working on creating new driver version. I think I'll be 
>>>> able to
>>>> sent it soon.
>>> Do you still plan to release a driver update for an i2c imx driver 
>>> slave support?
>>>
>>> Best regards,
>>> Jim Baxter
>>>
>

-- 
_______________________________________________
Joshua Frkuska | Embedded Software Engineer
Mentor Graphics Japan Co., ltd. | +81-3-6866-7611

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