linux-kernel - Re: [RFC/RFT 00/10] i2c: move handling of suspended adapters to the core

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Message-ID: <20181211234102.GA6701@kunai>
Date:   Wed, 12 Dec 2018 00:41:03 +0100
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Wolfram Sang <wsa+renesas@...g-engineering.com>,
        linux-i2c@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com,
        linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org
Subject: Re: [RFC/RFT 00/10] i2c: move handling of suspended adapters to the
 core

Hi Hans,

thanks for testing this series!

> Note that the i2c-sprd driver changes in your patchset also get close
> to triggering this problem, but they dodge the bullet because there
> are separate system-wide and runtime suspend handlers and only the
> system-wide handlers call the new i2c_mark_adapter_suspended() function.

Yes, this what I assumed to be all around - seperate handlers for RPM
and PM. And I also assumed that they could be seperated if they aren't
already. Until I read...

> As I explain in the commit message of the first attached patch
> simply always using split handlers is not really an option because
> of adapter drivers using DPM_FLAG_SMART_PREPARE or
> DPM_FLAG_SMART_SUSPEND.

... this. I don't know what these flags do (and reading SMART in there
gives me more a 'uh-oh' feeling) but if the handlers can't be split, the
issues you were seeing are a consequence, yes.

For me, this sadly spoils the whole concept. The patches you add make
things even more complicated. Not happy about that.

Looking at the open coded version you did for the designware driver, I
wonder now if it is better to just leave it at driver level? Need to
sleep over it, though.

Thanks again,

   Wolfram

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