linux-kernel - Re: [PATCH v7 12/34] i2c: tegra: Use clk-bulk helpers

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Date:   Mon, 21 Sep 2020 14:15:09 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Dmitry Osipenko <digetx@...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>
Subject: Re: [PATCH v7 12/34] i2c: tegra: Use clk-bulk helpers

On Mon, Sep 21, 2020 at 2:02 PM Thierry Reding <thierry.reding@...il.com> wrote:
> On Thu, Sep 17, 2020 at 04:54:28PM +0300, Andy Shevchenko wrote:
> > On Thu, Sep 17, 2020 at 2:38 PM Thierry Reding <thierry.reding@...il.com> wrote:
> > > On Wed, Sep 09, 2020 at 01:39:44AM +0300, Dmitry Osipenko wrote:

...

> > > This is tempting from a diffstat point of view, but the downside is that
> > > we can now no longer validate that all of the necessary clocks are given
> > > in device tree.
> > >
> > > Previously the driver would fail to probe the I2C controller if any of
> > > the expected clocks were not defined in device tree, but now it's just
> > > going to continue without it and not give any indication as to what's
> > > wrong.
> >
> > You may print an error in the error path as previously. Since both
> > clocks are mandatory (as far as I understood the code) user will need
> > to check DT in any case.
>
> The problem is that the number of required clocks depends on the variant
> of the IP block that's implemented. Some require just one clock and
> others require two or three. With this patch the driver is just going to
> pick whatever clocks are given in device tree, but it removes any
> possibility of detecting whether the device trees contain the correct
> clocks. So we may very well run into a situation where the driver now
> successfully probes but then malfunctions because one or more of the
> clocks were not specified in device tree.
>
> Thierry

I still failed to get this. Are you suggesting that CCF bulk
operations are fundamentally broken?

In the above case one may add more checks. AFAICS is_vi won't be
removed, so can be easily checked.
Basically that for-loop for div_clk is questionable. I agree on that.


-- 
With Best Regards,
Andy Shevchenko