linux-kernel - Re: [PATCH v3 05/22] i2c: tegra: Use reset_control

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Message-ID: <07e418bb-77c1-a3bc-bb8b-b930b8c723df@gmail.com>
Date:   Thu, 3 Sep 2020 16:47:10 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        linux-tegra@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>
Subject: Re: [PATCH v3 05/22] i2c: tegra: Use reset_control_reset()

03.09.2020 14:11, Andy Shevchenko пишет:
> On Thu, Sep 3, 2020 at 3:53 AM Dmitry Osipenko <digetx@...il.com> wrote:
>>
>> Use a single reset_control_reset() instead of assert/deasset couple in
>> order to make code cleaner a tad.
> 
>> Note that the reset_control_reset()
>> uses 1 microsecond delay instead of 2 that was used previously, but this
>> shouldn't matter.
> 
> What datasheet says about this delay?

The public datasheet doesn't say anything specific about the I2C
controller reset time. IIUC, controller logic runs at 200/400 MHz, so
1us should be enough for the reset.

I'm sure that somebody from NVIDIA should know the exact answer and will
correct me if I'm wrong. I CC'd Peter De Schrijver who is a maintainer
of the Tegra's clock-and-reset driver.