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References: <20220223105600.1132593-1-maxime@cerno.tech> <20220223105600.1132593-3-maxime@cerno.tech> <CAGS_qxqNU+rGFuALEpmqqmtD+LsTQ4R3_WWL3M70Ar-_af6OnA@mail.gmail.com> <20220224225422.98298C340E9@smtp.kernel.org> <20220225142606.6xpq4nzh7ldtkekk@houat>
Subject: Re: [PATCH v6 02/12] clk: Introduce Kunit Tests for the framework
From:   Stephen Boyd <sboyd@kernel.org>
Cc:     Daniel Latypov <dlatypov@google.com>,
        Mike Turquette <mturquette@baylibre.com>,
        linux-clk@vger.kernel.org,
        Dave Stevenson <dave.stevenson@raspberrypi.com>,
        Phil Elwell <phil@raspberrypi.com>,
        Tim Gover <tim.gover@raspberrypi.com>,
        Dom Cobley <dom@raspberrypi.com>,
        dri-devel@lists.freedesktop.org, kunit-dev@googlegroups.com
To:     Maxime Ripard <maxime@cerno.tech>
Date:   Fri, 25 Feb 2022 14:44:04 -0800
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Quoting Maxime Ripard (2022-02-25 06:26:06)
> Hi Stephen,
>=20
> On Thu, Feb 24, 2022 at 02:54:20PM -0800, Stephen Boyd wrote:
> > Quoting Daniel Latypov (2022-02-23 14:50:59)
> > > On Wed, Feb 23, 2022 at 2:56 AM Maxime Ripard <maxime@cerno.tech> wro=
te:
> > > Incremental coverage for 3/9 files in --diff_file
> > > Total incremental: 99.29% coverage (281/283 lines)
> > >   drivers/clk/clk.c: 84.62% coverage (11/13 lines)
> > >   drivers/clk/clk_test.c: 100.00% coverage (269/269 lines)
> > >   include/linux/clk.h: 100.00% coverage (1/1 lines)
> > >=20
> > > Missing lines are drivers/clk/clk.c:2397-8, i.e. this part of the dif=
f:
> > > +       if (ret) {
> > > +               /* rollback the changes */
> > > +               clk->min_rate =3D old_min; <- 2397
> > > +               clk->max_rate =3D old_max; <- 2398
> > >=20
> > > These are from before and were just moved around.
> >=20
> > We could trigger a failure in the provider when the rate is set, and
> > then we could call round_rate() again and make sure the boundaries from
> > before are maintained.
>=20
> I tried to do that, and it turns out we can't, since we ignore the
> set_rate return code:
>=20
> https://elixir.bootlin.com/linux/latest/source/drivers/clk/clk.c#L2107
>=20
> We could make determine_rate fail, but then clk_round_rate would fail as
> well and wouldn't allow us to test whether the boundaries are still in
> place.
>=20

The test could still do it at a high level right? And when/if we decide
to bubble up the set_rate failure then we would be testing these lines.
Seems like a good idea to implement it with a TODO note that clk.c is
ignoring the set_rate clk_op returning failure.