linux-kernel - Re: I2C PM overhaul needed? (Re: [PATCH 1/2] i2c: sprd: Prevent i2c accesses after suspend is called)

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Message-ID: <20180505015458.GM13402@sirena.org.uk>
Date:   Sat, 5 May 2018 10:54:58 +0900
From:   Mark Brown <broonie@...nel.org>
To:     Wolfram Sang <wsa@...-dreams.de>
Cc:     Grygorii Strashko <grygorii.strashko@...com>,
        Baolin Wang <baolin.wang@...aro.org>,
        linux-i2c@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: I2C PM overhaul needed? (Re: [PATCH 1/2] i2c: sprd: Prevent i2c
 accesses after suspend is called)

On Fri, May 04, 2018 at 02:24:47PM +0200, Wolfram Sang wrote:

> To handle that, I imagined an additional adapter callback like
> 'master_xfer_irqless' to be used for such special I2C messages. These
> kind of special messages could be tagged with a new I2C_M_something
> flag.

> And maybe this could be used here, too? Introduce this flag for very
> late/early messages. If they have it, messages are even sent in
> suspend_noirq() phase with the master_xfer_irqless() callback, otherwise
> we will have the WARNing printed out.

It feels like it'd be more elegant to have the core select the irqless
function automatically if called after interrupts have been disabled -
otherwise we end up with the need to special case through other layers
of the stack like regmap as well which seems like it'd be error prone.
OTOH it does mean we might not notice things happening later than they
should so it's not 100% clear...

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