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From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Mon, 16 Oct 2023 12:11:49 +0200
Message-ID: <CAPDyKFreG1Umg3G0+MBrXYcQhHytch3AzWmUWd=xHrCNNGnULA@mail.gmail.com>
Subject: Re: [PATCH 4/5] OPP: Remove genpd_virt_dev_lock
To:     Viresh Kumar <viresh.kumar@linaro.org>
Cc:     Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
        Stephen Boyd <sboyd@kernel.org>, linux-pm@vger.kernel.org,
        Vincent Guittot <vincent.guittot@linaro.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        linux-kernel@vger.kernel.org
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Precedence: bulk

On Fri, 13 Oct 2023 at 10:49, Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> All the config operations for OPP tables share common code paths now and
> none of the other ones have such protection in place. Either all should
> have it or none.
>
> The understanding here is that user won't clear the OPP configs while
> still using them and so such a case won't happen. We can always come
> back and use a wider lock for all resource types if required.
>
> Also fix the error on failing to allocate memory.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

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

Kind regards
Uffe


> ---
>  drivers/opp/core.c | 33 +++------------------------------
>  drivers/opp/opp.h  |  2 --
>  2 files changed, 3 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index 3516e79cf743..befe46036ad5 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -1089,12 +1089,6 @@ static int _opp_set_required_opps_genpd(struct device *dev,
>                 delta = -1;
>         }
>
> -       /*
> -        * Acquire genpd_virt_dev_lock to make sure we don't use a genpd_dev
> -        * after it is freed from another thread.
> -        */
> -       mutex_lock(&opp_table->genpd_virt_dev_lock);
> -
>         while (index != target) {
>                 ret = _set_performance_state(dev, genpd_virt_devs[index], opp, index);
>                 if (ret)
> @@ -1103,8 +1097,6 @@ static int _opp_set_required_opps_genpd(struct device *dev,
>                 index += delta;
>         }
>
> -       mutex_unlock(&opp_table->genpd_virt_dev_lock);
> -
>         return 0;
>  }
>
> @@ -1474,7 +1466,6 @@ static struct opp_table *_allocate_opp_table(struct device *dev, int index)
>                 return ERR_PTR(-ENOMEM);
>
>         mutex_init(&opp_table->lock);
> -       mutex_init(&opp_table->genpd_virt_dev_lock);
>         INIT_LIST_HEAD(&opp_table->dev_list);
>         INIT_LIST_HEAD(&opp_table->lazy);
>
> @@ -1510,7 +1501,6 @@ static struct opp_table *_allocate_opp_table(struct device *dev, int index)
>  remove_opp_dev:
>         _of_clear_opp_table(opp_table);
>         _remove_opp_dev(opp_dev, opp_table);
> -       mutex_destroy(&opp_table->genpd_virt_dev_lock);
>         mutex_destroy(&opp_table->lock);
>  err:
>         kfree(opp_table);
> @@ -1678,7 +1668,6 @@ static void _opp_table_kref_release(struct kref *kref)
>         list_for_each_entry_safe(opp_dev, temp, &opp_table->dev_list, node)
>                 _remove_opp_dev(opp_dev, opp_table);
>
> -       mutex_destroy(&opp_table->genpd_virt_dev_lock);
>         mutex_destroy(&opp_table->lock);
>         kfree(opp_table);
>  }
> @@ -2395,7 +2384,7 @@ static void _opp_put_config_regulators_helper(struct opp_table *opp_table)
>                 opp_table->config_regulators = NULL;
>  }
>
> -static void _detach_genpd(struct opp_table *opp_table)
> +static void _opp_detach_genpd(struct opp_table *opp_table)
>  {
>         int index;
>
> @@ -2449,13 +2438,11 @@ static int _opp_attach_genpd(struct opp_table *opp_table, struct device *dev,
>         if (!opp_table->required_opp_count)
>                 return -EPROBE_DEFER;
>
> -       mutex_lock(&opp_table->genpd_virt_dev_lock);
> -
>         opp_table->genpd_virt_devs = kcalloc(opp_table->required_opp_count,
>                                              sizeof(*opp_table->genpd_virt_devs),
>                                              GFP_KERNEL);
>         if (!opp_table->genpd_virt_devs)
> -               goto unlock;
> +               return -ENOMEM;
>
>         while (*name) {
>                 if (index >= opp_table->required_opp_count) {
> @@ -2478,29 +2465,15 @@ static int _opp_attach_genpd(struct opp_table *opp_table, struct device *dev,
>
>         if (virt_devs)
>                 *virt_devs = opp_table->genpd_virt_devs;
> -       mutex_unlock(&opp_table->genpd_virt_dev_lock);
>
>         return 0;
>
>  err:
> -       _detach_genpd(opp_table);
> -unlock:
> -       mutex_unlock(&opp_table->genpd_virt_dev_lock);
> +       _opp_detach_genpd(opp_table);
>         return ret;
>
>  }
>
> -static void _opp_detach_genpd(struct opp_table *opp_table)
> -{
> -       /*
> -        * Acquire genpd_virt_dev_lock to make sure virt_dev isn't getting
> -        * used in parallel.
> -        */
> -       mutex_lock(&opp_table->genpd_virt_dev_lock);
> -       _detach_genpd(opp_table);
> -       mutex_unlock(&opp_table->genpd_virt_dev_lock);
> -}
> -
>  static void _opp_clear_config(struct opp_config_data *data)
>  {
>         if (data->flags & OPP_CONFIG_GENPD)
> diff --git a/drivers/opp/opp.h b/drivers/opp/opp.h
> index fefdf9845692..08366f90f16b 100644
> --- a/drivers/opp/opp.h
> +++ b/drivers/opp/opp.h
> @@ -160,7 +160,6 @@ enum opp_table_access {
>   * @rate_clk_single: Currently configured frequency for single clk.
>   * @current_opp: Currently configured OPP for the table.
>   * @suspend_opp: Pointer to OPP to be used during device suspend.
> - * @genpd_virt_dev_lock: Mutex protecting the genpd virtual device pointers.
>   * @genpd_virt_devs: List of virtual devices for multiple genpd support.
>   * @required_opp_tables: List of device OPP tables that are required by OPPs in
>   *             this table.
> @@ -212,7 +211,6 @@ struct opp_table {
>         struct dev_pm_opp *current_opp;
>         struct dev_pm_opp *suspend_opp;
>
> -       struct mutex genpd_virt_dev_lock;
>         struct device **genpd_virt_devs;
>         struct opp_table **required_opp_tables;
>         unsigned int required_opp_count;
> --
> 2.31.1.272.g89b43f80a514
>