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

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Message-ID: <7b93f6b0-0e09-d8e0-b48e-4ef518c3bd9f@nvidia.com>
Date:   Wed, 30 May 2018 16:29:45 +0530
From:   Laxman Dewangan <ldewangan@...dia.com>
To:     Wolfram Sang <wsa@...-dreams.de>,
        Dmitry Osipenko <digetx@...il.com>
CC:     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



On Tuesday 29 May 2018 11:36 PM, Wolfram Sang wrote:
>>> 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?
Fine with me. Please add my Ack

Acked-by: Laxman Dewangan <ldewangan@...dia.com>