On Fri, 29 Apr 2022 at 18:08, Ansuel Smith <ansuelsmth@xxxxxxxxx> wrote:
>
> On Fri, Apr 29, 2022 at 05:53:32PM +0300, Dmitry Baryshkov wrote:
> > On 29/04/2022 15:01, Ansuel Smith wrote:
> > > Check if hw_parent is present before calculating the round_rate to
> > > prevent kernel panic. On error -EINVAL is reported.
> > >
> > > Signed-off-by: Ansuel Smith <ansuelsmth@xxxxxxxxx>
> >
> > I see that other clock drivers do not perform this check. Which path leads
> > to this oops?
> >
>
> This comes from qsdk patches so I apologize in advance about this.
Ugh. If it comes from the code authored by somebody else, it'd be
better to note this (by using the From or Co-developed-by tags).
At the very least (if the author is unknown) you can mention the
origin of the patch (qsdk) in the commit message.
>
> Anyway I'm checking the code and krait-cc is the only user of
> krait_div2_clk_ops. That user have as parent only hfpll_something that
> is declared by gcc. Now hfpll can also be declared in dts with a
> dedicated driver so I wonder if the problem is there in the case when
> hfpll is declared in dts and is probed after krait-cc. This is not the
> case for ipq8064 but I wonder if qsdk have other krait based device that
> have a configuration with hfpll declared in dts.
On msm8974 (and maybe others) the hfpll should be driven by the
separate hfpll driver.
>
> In short you are right and in our current code the check is uselss and
> I'm positive about dropping this patch but I do wonder if downstream
> there is an actual use of this. Don't know how to proceed. Any hint?
I'd say, let's drop it for now unless Stephen or Bjorn tell us that
it's a valid check.
>
> > > ---
> > > drivers/clk/qcom/clk-krait.c | 7 ++++++-
> > > 1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/clk/qcom/clk-krait.c b/drivers/clk/qcom/clk-krait.c
> > > index 90046428693c..6c367ad6506a 100644
> > > --- a/drivers/clk/qcom/clk-krait.c
> > > +++ b/drivers/clk/qcom/clk-krait.c
> > > @@ -84,7 +84,12 @@ EXPORT_SYMBOL_GPL(krait_mux_clk_ops);
> > > static long krait_div2_round_rate(struct clk_hw *hw, unsigned long rate,
> > > unsigned long *parent_rate)
> > > {
> > > - *parent_rate = clk_hw_round_rate(clk_hw_get_parent(hw), rate * 2);
> > > + struct clk_hw *hw_parent = clk_hw_get_parent(hw);
> > > +
> > > + if (!hw_parent)
> > > + return -EINVAL;
> > > +
> > > + *parent_rate = clk_hw_round_rate(hw_parent, rate * 2);
> > > return DIV_ROUND_UP(*parent_rate, 2);
> > > }
> >
> >
> > --
> > With best wishes
> > Dmitry
>
> --
> Ansuel
--
With best wishes
Dmitry
