linux-kernel - Re: [PATCH v3 5/6] clk: samsung: Extract parent clock enabling to common function

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Date:   Mon, 6 Mar 2023 17:47:56 -0600
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Chanho Park <chanho61.park@...sung.com>,
        David Virag <virag.david003@...il.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        linux-samsung-soc@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/6] clk: samsung: Extract parent clock enabling to
 common function

On Mon, 6 Mar 2023 at 08:35, Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 23/02/2023 05:19, Sam Protsenko wrote:
> > Extract parent clock enabling from exynos_arm64_register_cmu() to
> > dedicated function.
> >
> > Acked-by: Marek Szyprowski <m.szyprowski@...sung.com>
> > Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> > Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
> > ---
> > Changes in v3:
> >   - Rebased on top of latest soc/for-next tree
> >   - Added Marek's Acked-by tag
> >
> > Changes in v2:
> >   - Rebased on top of latest soc/for-next tree
> >   - Improved English in kernel doc comment
> >   - Added clk_prepare_enable() return value check
> >   - Added exynos_arm64_enable_bus_clk() check in
> >     exynos_arm64_register_cmu()
> >   - Changed the commit message to reflect code changes
> >
> >  drivers/clk/samsung/clk-exynos-arm64.c | 51 ++++++++++++++++++--------
> >  1 file changed, 35 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/clk/samsung/clk-exynos-arm64.c b/drivers/clk/samsung/clk-exynos-arm64.c
> > index b921b9a1134a..2aa3f0a5644e 100644
> > --- a/drivers/clk/samsung/clk-exynos-arm64.c
> > +++ b/drivers/clk/samsung/clk-exynos-arm64.c
> > @@ -56,6 +56,37 @@ static void __init exynos_arm64_init_clocks(struct device_node *np,
> >       iounmap(reg_base);
> >  }
> >
> > +/**
> > + * exynos_arm64_enable_bus_clk - Enable parent clock of specified CMU
> > + *
> > + * @dev:     Device object; may be NULL if this function is not being
> > + *           called from platform driver probe function
> > + * @np:              CMU device tree node
> > + * @cmu:     CMU data
> > + *
> > + * Keep CMU parent clock running (needed for CMU registers access).
> > + *
> > + * Return: 0 on success or a negative error code on failure.
> > + */
> > +static int __init exynos_arm64_enable_bus_clk(struct device *dev,
> > +             struct device_node *np, const struct samsung_cmu_info *cmu)
> > +{
> > +     struct clk *parent_clk;
> > +
> > +     if (!cmu->clk_name)
> > +             return 0;
> > +
> > +     if (dev)
> > +             parent_clk = clk_get(dev, cmu->clk_name);
> > +     else
> > +             parent_clk = of_clk_get_by_name(np, cmu->clk_name);
> > +
> > +     if (IS_ERR(parent_clk))
> > +             return PTR_ERR(parent_clk);
> > +
> > +     return clk_prepare_enable(parent_clk);
> > +}
> > +
> >  /**
> >   * exynos_arm64_register_cmu - Register specified Exynos CMU domain
> >   * @dev:     Device object; may be NULL if this function is not being
> > @@ -72,23 +103,11 @@ static void __init exynos_arm64_init_clocks(struct device_node *np,
> >  void __init exynos_arm64_register_cmu(struct device *dev,
> >               struct device_node *np, const struct samsung_cmu_info *cmu)
> >  {
> > -     /* Keep CMU parent clock running (needed for CMU registers access) */
> > -     if (cmu->clk_name) {
> > -             struct clk *parent_clk;
> > -
> > -             if (dev)
> > -                     parent_clk = clk_get(dev, cmu->clk_name);
> > -             else
> > -                     parent_clk = of_clk_get_by_name(np, cmu->clk_name);
> > -
> > -             if (IS_ERR(parent_clk)) {
> > -                     pr_err("%s: could not find bus clock %s; err = %ld\n",
> > -                            __func__, cmu->clk_name, PTR_ERR(parent_clk));
> > -             } else {
> > -                     clk_prepare_enable(parent_clk);
> > -             }
> > -     }
> > +     int err;
> >
> > +     err = exynos_arm64_enable_bus_clk(dev, np, cmu);
> > +     if (err)
> > +             panic("%s: could not enable bus clock\n", __func__);
>
> The error handling is changed and not equivalent. I would say that we
> could still try to boot even if this failed, so kernel should not panic.
> Maybe the parent clock is enabled by bootloader.
>

Agreed, I've probably overlooked that one when making all the
refactoring. The same stands for the patch #6. Will rework and send
out those two separately soon, as the rest of patches you already
applied.

Thanks!

> Best regards,
> Krzysztof
>