Re: [PATCH v6 02/12] clk: Introduce Kunit Tests for the framework

[Stephen Boyd <sboyd@kernel.org>]

Quoting Maxime Ripard (2022-02-25 06:26:06)
> Hi Stephen,
> 
> 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> wrote:
> > > 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)
> > > 
> > > Missing lines are drivers/clk/clk.c:2397-8, i.e. this part of the diff:
> > > +       if (ret) {
> > > +               /* rollback the changes */
> > > +               clk->min_rate = old_min; <- 2397
> > > +               clk->max_rate = old_max; <- 2398
> > > 
> > > These are from before and were just moved around.
> > 
> > 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.
> 
> I tried to do that, and it turns out we can't, since we ignore the
> set_rate return code:
> 
> https://elixir.bootlin.com/linux/latest/source/drivers/clk/clk.c#L2107
> 
> 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.
> 

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.