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References: <20190724014222.110767-1-saravanak@google.com> <20190724014222.110767-4-saravanak@google.com>
 <41434f8279c7004737e19fe2fbad8f14@codeaurora.org>
In-Reply-To: <41434f8279c7004737e19fe2fbad8f14@codeaurora.org>
From:   Saravana Kannan <saravanak@google.com>
Date:   Wed, 24 Jul 2019 14:13:45 -0700
Message-ID: <CAGETcx9dGuj3dTFoJxO2xDqdA83pU041HQhMeW2qN0jvmuwA3Q@mail.gmail.com>
Subject: Re: [PATCH v4 3/5] OPP: Improve required-opps linking
To:     Sibi Sankar <sibis@codeaurora.org>
Cc:     MyungJoo Ham <myungjoo.ham@samsung.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
        Stephen Boyd <sboyd@kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Android Kernel Team <kernel-team@android.com>,
        Linux PM <linux-pm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-kernel-owner@vger.kernel.org
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Sender: linux-kernel-owner@vger.kernel.org
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:
On Wed, Jul 24, 2019 at 10:59 AM Sibi Sankar <sibis@codeaurora.org> wrote:
>
> Hey Saravana,
>
> Didn't get time to test v4 will
> give it a spin tomorrow. Just
> included some issues which should
> still remain in v4.

Thanks.

>
> On 2019-07-24 07:12, Saravana Kannan wrote:
> > Currently, the linking of required-opps fails silently if the
> > destination OPP table hasn't been added before the source OPP table is
> > added. This puts an unnecessary requirement that the destination table
> > be added before the source table is added.
> >
> > In reality, the destination table is needed only when we try to
> > translate from source OPP to destination OPP. So, instead of
> > completely failing, retry linking the tables when the translation is
> > attempted.
> >
> > Signed-off-by: Saravana Kannan <saravanak@google.com>
> > ---
> >  drivers/opp/core.c |  30 ++++++++++----
> >  drivers/opp/of.c   | 101 ++++++++++++++++++++++++---------------------
> >  drivers/opp/opp.h  |   5 +++
> >  3 files changed, 80 insertions(+), 56 deletions(-)
> >
> > diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> > index 5460b7da110e..01c71d145ec7 100644
> > --- a/drivers/opp/core.c
> > +++ b/drivers/opp/core.c
> > @@ -706,6 +706,9 @@ static int _set_required_opps(struct device *dev,
> >       if (!required_opp_tables)
> >               return 0;
> >
> > +     if (!_of_lazy_link_required_tables(opp_table))
> > +             return -EPROBE_DEFER;
> > +
> >       /* Single genpd case */
> >       if (!genpd_virt_devs && required_opp_tables[0]->is_genpd) {
> >               pstate = likely(opp) ? opp->required_opps[0]->pstate : 0;
> > @@ -726,11 +729,16 @@ static int _set_required_opps(struct device *dev,
> >       mutex_lock(&opp_table->genpd_virt_dev_lock);
> >
> >       for (i = 0; i < opp_table->required_opp_count; i++) {
> > -             pstate = likely(opp) ? opp->required_opps[i]->pstate : 0;
> > -
> >               if (!genpd_virt_devs[i])
> >                       continue;
> >
> > +             if (!opp->required_opps[i]) {
> > +                     ret = -ENODEV;
> > +                     break;
> > +             }
> > +
> > +             pstate = likely(opp) ? opp->required_opps[i]->pstate : 0;
> > +
> >               ret = dev_pm_genpd_set_performance_state(genpd_virt_devs[i],
> > pstate);
> >               if (ret) {
> >                       dev_err(dev, "Failed to set performance rate of %s: %d (%d)\n",
> > @@ -1906,8 +1914,11 @@ struct dev_pm_opp
> > *dev_pm_opp_xlate_required_opp(struct opp_table *src_table,
> >       if (!src_table || !dst_table || !src_opp)
> >               return NULL;
> >
> > +     _of_lazy_link_required_tables(src_table);
> > +
> >       for (i = 0; i < src_table->required_opp_count; i++) {
> > -             if (src_table->required_opp_tables[i]->np == dst_table->np)
> > +             if (src_table->required_opp_tables[i]
> > +                 && src_table->required_opp_tables[i]->np == dst_table->np)
> >                       break;
> >       }
> >
> > @@ -1970,6 +1981,8 @@ int dev_pm_opp_xlate_performance_state(struct
> > opp_table *src_table,
> >       if (!src_table->required_opp_count)
> >               return pstate;
> >
> > +     _of_lazy_link_required_tables(src_table);
> > +
> >       for (i = 0; i < src_table->required_opp_count; i++) {
> >               if (src_table->required_opp_tables[i]->np == dst_table->np)
> >                       break;
> > @@ -1985,15 +1998,16 @@ int dev_pm_opp_xlate_performance_state(struct
> > opp_table *src_table,
> >
> >       list_for_each_entry(opp, &src_table->opp_list, node) {
> >               if (opp->pstate == pstate) {
> > -                     dest_pstate = opp->required_opps[i]->pstate;
> > -                     goto unlock;
> > +                     if (opp->required_opps[i])
> > +                             dest_pstate = opp->required_opps[i]->pstate;
> > +                     break;
> >               }
> >       }
> >
> > -     pr_err("%s: Couldn't find matching OPP (%p: %p)\n", __func__,
> > src_table,
> > -            dst_table);
> > +     if (dest_pstate < 0)
> > +             pr_err("%s: Couldn't find matching OPP (%p: %p)\n", __func__,
> > +                    src_table, dst_table);
> >
> > -unlock:
> >       mutex_unlock(&src_table->lock);
> >
> >       return dest_pstate;
> > diff --git a/drivers/opp/of.c b/drivers/opp/of.c
> > index ff88eaf66b56..1f2860b2d6e5 100644
> > --- a/drivers/opp/of.c
> > +++ b/drivers/opp/of.c
> > @@ -145,7 +145,7 @@ static void _opp_table_free_required_tables(struct
> > opp_table *opp_table)
> >
> >       for (i = 0; i < opp_table->required_opp_count; i++) {
> >               if (IS_ERR_OR_NULL(required_opp_tables[i]))
> > -                     break;
> > +                     continue;
> >
> >               dev_pm_opp_put_opp_table(required_opp_tables[i]);
> >       }
> > @@ -165,8 +165,8 @@ static void
> > _opp_table_alloc_required_tables(struct opp_table *opp_table,
> >                                            struct device_node *opp_np)
> >  {
> >       struct opp_table **required_opp_tables;
> > -     struct device_node *required_np, *np;
> > -     int count, i;
> > +     struct device_node *np;
> > +     int count;
> >
> >       /* Traversing the first OPP node is all we need */
> >       np = of_get_next_available_child(opp_np, NULL);
> > @@ -176,35 +176,65 @@ static void
> > _opp_table_alloc_required_tables(struct opp_table *opp_table,
> >       }
> >
> >       count = of_count_phandle_with_args(np, "required-opps", NULL);
> > +     of_node_put(np);
> >       if (!count)
>
> should this be count <= 0 instead ?

Looks like in the current implementation of
of_count_phandle_with_args() returns 0 if the required-opps property
doesn't exist. It can return errors only if the phandles are invalid
(hopefully DTC would catch that) or if the "cells" param is listed by
the DT node doesn't have it. The later is not a problem here since
cells is NULL.

But I think what you suggested would be safer if the other error cases
aren't caught by the DTC. But this is existing code and I don't want
to fix unrelated stuff in this patch.

> > -             goto put_np;
> > +             return;
> >
> >       required_opp_tables = kcalloc(count, sizeof(*required_opp_tables),
> >                                     GFP_KERNEL);
> >       if (!required_opp_tables)
> > -             goto put_np;
> > +             return;
> >
> >       opp_table->required_opp_tables = required_opp_tables;
> >       opp_table->required_opp_count = count;
>
> error values could be assigned to
> unsigned int member required_opp_count

That's assuming a ~4GB kernel malloc succeeds :) Still a valid point,
but don't want to fix that in this patch series.

> > +}
> > +
> > +/*
> > + * Try to link all required tables and return true if all of them have
> > been
> > + * linked. Otherwise, return false.
> > + */
> > +bool _of_lazy_link_required_tables(struct opp_table *src)
> > +{
> > +     struct dev_pm_opp *src_opp, *tmp_opp;
> > +     struct opp_table *req_table;
> > +     struct device_node *req_np;
> > +     int i, num_linked = 0;
> >
> > -     for (i = 0; i < count; i++) {
> > -             required_np = of_parse_required_opp(np, i);
> > -             if (!required_np)
> > -                     goto free_required_tables;
> > +     mutex_lock(&src->lock);
> >
> > -             required_opp_tables[i] = _find_table_of_opp_np(required_np);
> > -             of_node_put(required_np);
> > +     if (list_empty(&src->opp_list))
> > +             goto out;
> >
> > -             if (IS_ERR(required_opp_tables[i]))
> > -                     goto free_required_tables;
> > -     }
> > +     src_opp = list_first_entry(&src->opp_list, struct dev_pm_opp, node);
> >
> > -     goto put_np;
> > +     for (i = 0; i < src->required_opp_count; i++) {
> > +             if (src->required_opp_tables[i]) {
> > +                     num_linked++;
> > +                     continue;
> > +             }
> >
> > -free_required_tables:
> > -     _opp_table_free_required_tables(opp_table);
> > -put_np:
> > -     of_node_put(np);
> > +             req_np = of_parse_required_opp(src_opp->np, i);
> > +             if (!req_np)
> > +                     continue;
> > +
> > +             req_table = _find_table_of_opp_np(req_np);
> > +             of_node_put(req_np);
> > +             if (!req_table)
>
> should be IS_ERR instead since
> req_table could be ERR_PTR(-ENODEV)

Will fix in the next version.

>
> > +                     continue;
> > +
> > +             src->required_opp_tables[i] = req_table;
> > +             list_for_each_entry(tmp_opp, &src->opp_list, node) {
> > +                     req_np = of_parse_required_opp(tmp_opp->np, i);
> > +                     tmp_opp->required_opps[i] = _find_opp_of_np(req_table,
> > +                                                                 req_np);
> > +                     of_node_put(req_np);
> > +             }
> > +             num_linked++;
> > +     }
> > +
> > +out:
> > +     mutex_unlock(&src->lock);
> > +     return num_linked == src->required_opp_count;
> >  }
> >
> >  void _of_init_opp_table(struct opp_table *opp_table, struct device
> > *dev,
> > @@ -267,7 +297,7 @@ void _of_opp_free_required_opps(struct opp_table
> > *opp_table,
> >
> >       for (i = 0; i < opp_table->required_opp_count; i++) {
> >               if (!required_opps[i])
> > -                     break;
> > +                     continue;
> >
> >               /* Put the reference back */
> >               dev_pm_opp_put(required_opps[i]);
> > @@ -282,9 +312,7 @@ static int _of_opp_alloc_required_opps(struct
> > opp_table *opp_table,
> >                                      struct dev_pm_opp *opp)
> >  {
> >       struct dev_pm_opp **required_opps;
> > -     struct opp_table *required_table;
> > -     struct device_node *np;
> > -     int i, ret, count = opp_table->required_opp_count;
> > +     int count = opp_table->required_opp_count;
> >
> >       if (!count)
> >               return 0;
> > @@ -295,32 +323,7 @@ static int _of_opp_alloc_required_opps(struct
> > opp_table *opp_table,
> >
> >       opp->required_opps = required_opps;
> >
> > -     for (i = 0; i < count; i++) {
> > -             required_table = opp_table->required_opp_tables[i];
> > -
> > -             np = of_parse_required_opp(opp->np, i);
> > -             if (unlikely(!np)) {
> > -                     ret = -ENODEV;
> > -                     goto free_required_opps;
> > -             }
> > -
> > -             required_opps[i] = _find_opp_of_np(required_table, np);
> > -             of_node_put(np);
> > -
> > -             if (!required_opps[i]) {
> > -                     pr_err("%s: Unable to find required OPP node: %pOF (%d)\n",
> > -                            __func__, opp->np, i);
> > -                     ret = -ENODEV;
> > -                     goto free_required_opps;
> > -             }
> > -     }
> > -
> >       return 0;
> > -
> > -free_required_opps:
> > -     _of_opp_free_required_opps(opp_table, opp);
> > -
> > -     return ret;
> >  }
> >
> >  static bool _opp_is_supported(struct device *dev, struct opp_table
> > *opp_table,
> > @@ -687,6 +690,8 @@ static int _of_add_opp_table_v2(struct device
> > *dev, struct opp_table *opp_table)
> >       if (pstate_count)
> >               opp_table->genpd_performance_state = true;
> >
> > +     _of_lazy_link_required_tables(opp_table);
> > +
> >       opp_table->parsed_static_opps = true;
> >
> >       return 0;
> > diff --git a/drivers/opp/opp.h b/drivers/opp/opp.h
> > index 01a500e2c40a..77e8394fd0fe 100644
> > --- a/drivers/opp/opp.h
> > +++ b/drivers/opp/opp.h
> > @@ -223,12 +223,17 @@ void _put_opp_list_kref(struct opp_table
> > *opp_table);
> >  void _of_init_opp_table(struct opp_table *opp_table, struct device
> > *dev, int index);
> >  void _of_clear_opp_table(struct opp_table *opp_table);
> >  struct opp_table *_managed_opp(struct device *dev, int index);
> > +bool _of_lazy_link_required_tables(struct opp_table *src);
> >  void _of_opp_free_required_opps(struct opp_table *opp_table,
> >                               struct dev_pm_opp *opp);
> >  #else
> >  static inline void _of_init_opp_table(struct opp_table *opp_table,
> > struct device *dev, int index) {}
> >  static inline void _of_clear_opp_table(struct opp_table *opp_table) {}
> >  static inline struct opp_table *_managed_opp(struct device *dev, int
> > index) { return NULL; }
> > +bool _of_lazy_link_required_tables(struct opp_table *src)
>
> should be static inline bool

Thanks. Good catch.

>
> > +{
> > +     return true;
> > +}
> >  static inline void _of_opp_free_required_opps(struct opp_table
> > *opp_table,
> >                                             struct dev_pm_opp *opp) {}
> >  #endif
>

I'll send out a v5 series after Viresh takes a look at this and
confirms this design is okay.

-Saravana