linux-kernel - Re: [PATCH v11 3/4] i2c: aspeed: added driver for Aspeed I2C

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Date:   Tue, 27 Jun 2017 01:28:31 -0700
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     Wolfram Sang <wsa@...-dreams.de>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        gregkh@...uxfoundation.org, davem@...emloft.net,
        mchehab@...nel.org, Joel Stanley <joel@....id.au>,
        martin.petersen@...cle.com,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>
Subject: Re: [PATCH v11 3/4] i2c: aspeed: added driver for Aspeed I2C

On Fri, Jun 23, 2017 at 11:43 AM, Wolfram Sang <wsa@...-dreams.de> wrote:
> On Tue, Jun 20, 2017 at 02:15:15PM -0700, Brendan Higgins wrote:
>> Added initial master support for Aspeed I2C controller. Supports
>> fourteen busses present in AST24XX and AST25XX BMC SoCs by Aspeed.
>>
>> Signed-off-by: Brendan Higgins <brendanhiggins@...gle.com>
>
> Applied to for-next, thanks for all the hard work!

Thanks for the patience!

>
> One question however which can be solved incrementally if needed:
>
>> +     if (command & ASPEED_I2CD_SDA_LINE_STS) {
>> +             /* Bus is idle: no recovery needed. */
>> +             if (command & ASPEED_I2CD_SCL_LINE_STS)
>> +                     goto out;
>> +             dev_dbg(bus->dev, "SCL hung (state %x), attempting recovery\n",
>> +                     command);
>> +
>> +             reinit_completion(&bus->cmd_complete);
>> +             writel(ASPEED_I2CD_M_STOP_CMD, bus->base + ASPEED_I2C_CMD_REG);
>
> If SCL is stuck low, how do you want to send a STOP?
>

Fair point. I should probably drop that in the future and just do a
reset, and even then, doing a
reset is probably just wishful thinking. If a slave is holding down
SCL, we are pretty screwed.