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In-Reply-To: <36de122e568dcba371d3581e5f936243b405a874.1698661048.git.viresh.kumar@linaro.org>
From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Mon, 6 Nov 2023 16:41:18 +0100
Message-ID: <CAPDyKFpsfzdarSz5h_XuyLbfXKCWPQdV5M+mOb_Q6GhhgzCXAA@mail.gmail.com>
Subject: Re: [PATCH V2 1/3] OPP: Level zero is valid
To:     Viresh Kumar <viresh.kumar@linaro.org>
Cc:     Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
        Stephen Boyd <sboyd@kernel.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>, linux-pm@vger.kernel.org,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Stephan Gerhold <stephan.gerhold@kernkonzept.com>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Mon, 30 Oct 2023 at 11:24, Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> The level zero can be used by some OPPs to drop performance state vote
> for the device. It is perfectly fine to allow the same.
>
> _set_opp_level() considers it as an invalid value currently and returns
> early.
>
> In order to support this properly, initialize the level field with
> U32_MAX, which denotes unused level field.
>
> Reported-by: Stephan Gerhold <stephan.gerhold@kernkonzept.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>

Kind regards
Uffe


> ---
>  drivers/opp/core.c     | 24 ++++++++++++++++++++----
>  drivers/opp/of.c       |  8 +++++++-
>  include/linux/pm_opp.h |  5 ++++-
>  3 files changed, 31 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index 84f345c69ea5..f2e2aa07b431 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -201,7 +201,7 @@ EXPORT_SYMBOL_GPL(dev_pm_opp_get_freq_indexed);
>   * @opp:       opp for which level value has to be returned for
>   *
>   * Return: level read from device tree corresponding to the opp, else
> - * return 0.
> + * return U32_MAX.
>   */
>  unsigned int dev_pm_opp_get_level(struct dev_pm_opp *opp)
>  {
> @@ -221,7 +221,7 @@ EXPORT_SYMBOL_GPL(dev_pm_opp_get_level);
>   * @index:     index of the required opp
>   *
>   * Return: performance state read from device tree corresponding to the
> - * required opp, else return 0.
> + * required opp, else return U32_MAX.
>   */
>  unsigned int dev_pm_opp_get_required_pstate(struct dev_pm_opp *opp,
>                                             unsigned int index)
> @@ -808,6 +808,14 @@ struct dev_pm_opp *dev_pm_opp_find_level_ceil(struct device *dev,
>         struct dev_pm_opp *opp;
>
>         opp = _find_key_ceil(dev, &temp, 0, true, _read_level, NULL);
> +
> +       /* False match */
> +       if (temp == OPP_LEVEL_UNSET) {
> +               dev_err(dev, "%s: OPP levels aren't available\n", __func__);
> +               dev_pm_opp_put(opp);
> +               return ERR_PTR(-ENODEV);
> +       }
> +
>         *level = temp;
>         return opp;
>  }
> @@ -1049,12 +1057,18 @@ static int _set_opp_bw(const struct opp_table *opp_table,
>  static int _set_performance_state(struct device *dev, struct device *pd_dev,
>                                   struct dev_pm_opp *opp, int i)
>  {
> -       unsigned int pstate = likely(opp) ? opp->required_opps[i]->level: 0;
> +       unsigned int pstate = 0;
>         int ret;
>
>         if (!pd_dev)
>                 return 0;
>
> +       if (likely(opp)) {
> +               pstate = opp->required_opps[i]->level;
> +               if (pstate == OPP_LEVEL_UNSET)
> +                       return 0;
> +       }
> +
>         ret = dev_pm_domain_set_performance_state(pd_dev, pstate);
>         if (ret) {
>                 dev_err(dev, "Failed to set performance state of %s: %d (%d)\n",
> @@ -1135,7 +1149,7 @@ static int _set_opp_level(struct device *dev, struct opp_table *opp_table,
>         int ret = 0;
>
>         if (opp) {
> -               if (!opp->level)
> +               if (opp->level == OPP_LEVEL_UNSET)
>                         return 0;
>
>                 level = opp->level;
> @@ -1867,6 +1881,8 @@ struct dev_pm_opp *_opp_allocate(struct opp_table *opp_table)
>
>         INIT_LIST_HEAD(&opp->node);
>
> +       opp->level = OPP_LEVEL_UNSET;
> +
>         return opp;
>  }
>
> diff --git a/drivers/opp/of.c b/drivers/opp/of.c
> index 81fa27599d58..85fad7ca0007 100644
> --- a/drivers/opp/of.c
> +++ b/drivers/opp/of.c
> @@ -1393,8 +1393,14 @@ int of_get_required_opp_performance_state(struct device_node *np, int index)
>
>         opp = _find_opp_of_np(opp_table, required_np);
>         if (opp) {
> -               pstate = opp->level;
> +               if (opp->level == OPP_LEVEL_UNSET) {
> +                       pr_err("%s: OPP levels aren't available for %pOF\n",
> +                              __func__, np);
> +               } else {
> +                       pstate = opp->level;
> +               }
>                 dev_pm_opp_put(opp);
> +
>         }
>
>         dev_pm_opp_put_opp_table(opp_table);
> diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
> index ccd97bcef269..af53101a1383 100644
> --- a/include/linux/pm_opp.h
> +++ b/include/linux/pm_opp.h
> @@ -92,9 +92,12 @@ struct dev_pm_opp_config {
>         struct device ***virt_devs;
>  };
>
> +#define OPP_LEVEL_UNSET                        U32_MAX
> +
>  /**
>   * struct dev_pm_opp_data - The data to use to initialize an OPP.
> - * @level: The performance level for the OPP.
> + * @level: The performance level for the OPP. Set level to OPP_LEVEL_UNSET if
> + * level field isn't used.
>   * @freq: The clock rate in Hz for the OPP.
>   * @u_volt: The voltage in uV for the OPP.
>   */
> --
> 2.31.1.272.g89b43f80a514
>