linux-kernel - Re: [PATCH v1] i2c: tegra: Remove suspend-resume

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Date:   Tue, 29 May 2018 20:06:59 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Laxman Dewangan <ldewangan@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Shardar Shariff Md <smohammed@...dia.com>,
        linux-tegra@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] i2c: tegra: Remove suspend-resume


> > Our I2C driver is based on the interrupt. So we have converted the
> > suspend/resume to suspend_noirq and reseume_noirq so that we will not allow the
> > transfer when system interrupt disabled in downstream.
> >           SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(tegra_i2c_suspend, tegra_i2c_resume)
> > 
> > In shutdown path, where interrupt disabled and still need i2c, we use the
> > bit-bang method via GPIO for i2c transfer.
> In the current upstream kernel suspend/resume can't be simply moved to the
> 'noirq' stage because resume invokes tegra_i2c_init() which uses runtime PM and
> that doesn't work with the IRQ's being disabled. But things do not work even
> with the tegra_i2c_init() changed to work with the disabled IRQ's, like I wrote
> above the I2C transfer fails (due to timeout) and a "fix" for that failure was
> to remove reset_control_assert/deassert from the tegra_i2c_init(). So I'd go for
> a complete suspend/resume removal for now as it is causes problem.

Laxman, are you convinced or do you have still objections?


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