Re: [PATCH V2 1/2] opp: Allow dev_pm_opp_get_opp_table() to return -EPROBE_DEFER

[Ulf Hansson]

On Mon, 24 Aug 2020 at 11:09, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
>
> From: Stephan Gerhold <stephan@xxxxxxxxxxx>
>
> The OPP core manages various resources, e.g. clocks or interconnect paths.
> These resources are looked up when the OPP table is allocated once
> dev_pm_opp_get_opp_table() is called the first time (either directly
> or indirectly through one of the many helper functions).
>
> At this point, the resources may not be available yet, i.e. looking them
> up will result in -EPROBE_DEFER. Unfortunately, dev_pm_opp_get_opp_table()
> is currently unable to propagate this error code since it only returns
> the allocated OPP table or NULL.
>
> This means that all consumers of the OPP core are required to make sure
> that all necessary resources are available. Usually this happens by
> requesting them, checking the result and releasing them immediately after.
>
> For example, we have added "dev_pm_opp_of_find_icc_paths(dev, NULL)" to
> several drivers now just to make sure the interconnect providers are
> ready before the OPP table is allocated. If this call is missing,
> the OPP core will only warn about this and then attempt to continue
> without interconnect. This will eventually fail horribly, e.g.:
>
>     cpu cpu0: _allocate_opp_table: Error finding interconnect paths: -517
>     ... later ...
>     of: _read_bw: Mismatch between opp-peak-kBps and paths (1 0)
>     cpu cpu0: _opp_add_static_v2: opp key field not found
>     cpu cpu0: _of_add_opp_table_v2: Failed to add OPP, -22
>
> This example happens when trying to use interconnects for a CPU OPP
> table together with qcom-cpufreq-nvmem.c. qcom-cpufreq-nvmem calls
> dev_pm_opp_set_supported_hw(), which ends up allocating the OPP table
> early. To fix the problem with the current approach we would need to add
> yet another call to dev_pm_opp_of_find_icc_paths(dev, NULL).
> But actually qcom-cpufreq-nvmem.c has nothing to do with interconnects...
>
> This commit attempts to make this more robust by allowing
> dev_pm_opp_get_opp_table() to return an error pointer. Fixing all
> the usages is trivial because the function is usually used indirectly
> through another helper (e.g. dev_pm_opp_set_supported_hw() above).
> These other helpers already return an error pointer.
>
> The example above then works correctly because set_supported_hw() will
> return -EPROBE_DEFER, and qcom-cpufreq-nvmem.c already propagates that
> error. It should also be possible to remove the remaining usages of
> "dev_pm_opp_of_find_icc_paths(dev, NULL)" from other drivers as well.
>
> Note that this commit currently only handles -EPROBE_DEFER for the
> clock/interconnects within _allocate_opp_table(). Other errors are just
> ignored as before. Eventually those should be propagated as well.
>
> Signed-off-by: Stephan Gerhold <stephan@xxxxxxxxxxx>

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

Kind regards
Uffe


> [ Viresh: skip checking return value of dev_pm_opp_get_opp_table() for
>           EPROBE_DEFER in domain.c, fix NULL return value and reorder
>           code a bit in core.c, and update exynos-asv.c ]
> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> ---
> Stephan, I have made some changes to the code. Please try it again and
> lemme know if it works fine.
>
>  drivers/base/power/domain.c      | 14 +++++----
>  drivers/opp/core.c               | 53 +++++++++++++++++++-------------
>  drivers/opp/of.c                 |  8 ++---
>  drivers/soc/samsung/exynos-asv.c |  2 +-
>  4 files changed, 44 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 2cb5e04cf86c..b92bb61550d3 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -2044,8 +2044,9 @@ int of_genpd_add_provider_simple(struct device_node *np,
>         if (genpd->set_performance_state) {
>                 ret = dev_pm_opp_of_add_table(&genpd->dev);
>                 if (ret) {
> -                       dev_err(&genpd->dev, "Failed to add OPP table: %d\n",
> -                               ret);
> +                       if (ret != -EPROBE_DEFER)
> +                               dev_err(&genpd->dev, "Failed to add OPP table: %d\n",
> +                                       ret);
>                         goto unlock;
>                 }
>
> @@ -2054,7 +2055,7 @@ int of_genpd_add_provider_simple(struct device_node *np,
>                  * state.
>                  */
>                 genpd->opp_table = dev_pm_opp_get_opp_table(&genpd->dev);
> -               WARN_ON(!genpd->opp_table);
> +               WARN_ON(IS_ERR(genpd->opp_table));
>         }
>
>         ret = genpd_add_provider(np, genpd_xlate_simple, genpd);
> @@ -2111,8 +2112,9 @@ int of_genpd_add_provider_onecell(struct device_node *np,
>                 if (genpd->set_performance_state) {
>                         ret = dev_pm_opp_of_add_table_indexed(&genpd->dev, i);
>                         if (ret) {
> -                               dev_err(&genpd->dev, "Failed to add OPP table for index %d: %d\n",
> -                                       i, ret);
> +                               if (ret != -EPROBE_DEFER)
> +                                       dev_err(&genpd->dev, "Failed to add OPP table for index %d: %d\n",
> +                                               i, ret);
>                                 goto error;
>                         }
>
> @@ -2121,7 +2123,7 @@ int of_genpd_add_provider_onecell(struct device_node *np,
>                          * performance state.
>                          */
>                         genpd->opp_table = dev_pm_opp_get_opp_table_indexed(&genpd->dev, i);
> -                       WARN_ON(!genpd->opp_table);
> +                       WARN_ON(IS_ERR(genpd->opp_table));
>                 }
>
>                 genpd->provider = &np->fwnode;
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index 6978b9218c6e..8c69a764d0a4 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -1068,7 +1068,7 @@ static struct opp_table *_allocate_opp_table(struct device *dev, int index)
>          */
>         opp_table = kzalloc(sizeof(*opp_table), GFP_KERNEL);
>         if (!opp_table)
> -               return NULL;
> +               return ERR_PTR(-ENOMEM);
>
>         mutex_init(&opp_table->lock);
>         mutex_init(&opp_table->genpd_virt_dev_lock);
> @@ -1079,8 +1079,8 @@ static struct opp_table *_allocate_opp_table(struct device *dev, int index)
>
>         opp_dev = _add_opp_dev(dev, opp_table);
>         if (!opp_dev) {
> -               kfree(opp_table);
> -               return NULL;
> +               ret = -ENOMEM;
> +               goto err;
>         }
>
>         _of_init_opp_table(opp_table, dev, index);
> @@ -1089,16 +1089,21 @@ static struct opp_table *_allocate_opp_table(struct device *dev, int index)
>         opp_table->clk = clk_get(dev, NULL);
>         if (IS_ERR(opp_table->clk)) {
>                 ret = PTR_ERR(opp_table->clk);
> -               if (ret != -EPROBE_DEFER)
> -                       dev_dbg(dev, "%s: Couldn't find clock: %d\n", __func__,
> -                               ret);
> +               if (ret == -EPROBE_DEFER)
> +                       goto err;
> +
> +               dev_dbg(dev, "%s: Couldn't find clock: %d\n", __func__, ret);
>         }
>
>         /* Find interconnect path(s) for the device */
>         ret = dev_pm_opp_of_find_icc_paths(dev, opp_table);
> -       if (ret)
> +       if (ret) {
> +               if (ret == -EPROBE_DEFER)
> +                       goto err;
> +
>                 dev_warn(dev, "%s: Error finding interconnect paths: %d\n",
>                          __func__, ret);
> +       }
>
>         BLOCKING_INIT_NOTIFIER_HEAD(&opp_table->head);
>         INIT_LIST_HEAD(&opp_table->opp_list);
> @@ -1107,6 +1112,10 @@ static struct opp_table *_allocate_opp_table(struct device *dev, int index)
>         /* Secure the device table modification */
>         list_add(&opp_table->node, &opp_tables);
>         return opp_table;
> +
> +err:
> +       kfree(opp_table);
> +       return ERR_PTR(ret);
>  }
>
>  void _get_opp_table_kref(struct opp_table *opp_table)
> @@ -1129,7 +1138,7 @@ static struct opp_table *_opp_get_opp_table(struct device *dev, int index)
>         if (opp_table) {
>                 if (!_add_opp_dev_unlocked(dev, opp_table)) {
>                         dev_pm_opp_put_opp_table(opp_table);
> -                       opp_table = NULL;
> +                       opp_table = ERR_PTR(-ENOMEM);
>                 }
>                 goto unlock;
>         }
> @@ -1573,8 +1582,8 @@ struct opp_table *dev_pm_opp_set_supported_hw(struct device *dev,
>         struct opp_table *opp_table;
>
>         opp_table = dev_pm_opp_get_opp_table(dev);
> -       if (!opp_table)
> -               return ERR_PTR(-ENOMEM);
> +       if (IS_ERR(opp_table))
> +               return opp_table;
>
>         /* Make sure there are no concurrent readers while updating opp_table */
>         WARN_ON(!list_empty(&opp_table->opp_list));
> @@ -1632,8 +1641,8 @@ struct opp_table *dev_pm_opp_set_prop_name(struct device *dev, const char *name)
>         struct opp_table *opp_table;
>
>         opp_table = dev_pm_opp_get_opp_table(dev);
> -       if (!opp_table)
> -               return ERR_PTR(-ENOMEM);
> +       if (IS_ERR(opp_table))
> +               return opp_table;
>
>         /* Make sure there are no concurrent readers while updating opp_table */
>         WARN_ON(!list_empty(&opp_table->opp_list));
> @@ -1725,8 +1734,8 @@ struct opp_table *dev_pm_opp_set_regulators(struct device *dev,
>         int ret, i;
>
>         opp_table = dev_pm_opp_get_opp_table(dev);
> -       if (!opp_table)
> -               return ERR_PTR(-ENOMEM);
> +       if (IS_ERR(opp_table))
> +               return opp_table;
>
>         /* This should be called before OPPs are initialized */
>         if (WARN_ON(!list_empty(&opp_table->opp_list))) {
> @@ -1833,8 +1842,8 @@ struct opp_table *dev_pm_opp_set_clkname(struct device *dev, const char *name)
>         int ret;
>
>         opp_table = dev_pm_opp_get_opp_table(dev);
> -       if (!opp_table)
> -               return ERR_PTR(-ENOMEM);
> +       if (IS_ERR(opp_table))
> +               return opp_table;
>
>         /* This should be called before OPPs are initialized */
>         if (WARN_ON(!list_empty(&opp_table->opp_list))) {
> @@ -1901,8 +1910,8 @@ struct opp_table *dev_pm_opp_register_set_opp_helper(struct device *dev,
>                 return ERR_PTR(-EINVAL);
>
>         opp_table = dev_pm_opp_get_opp_table(dev);
> -       if (!opp_table)
> -               return ERR_PTR(-ENOMEM);
> +       if (!IS_ERR(opp_table))
> +               return opp_table;
>
>         /* This should be called before OPPs are initialized */
>         if (WARN_ON(!list_empty(&opp_table->opp_list))) {
> @@ -1982,8 +1991,8 @@ struct opp_table *dev_pm_opp_attach_genpd(struct device *dev,
>         const char **name = names;
>
>         opp_table = dev_pm_opp_get_opp_table(dev);
> -       if (!opp_table)
> -               return ERR_PTR(-ENOMEM);
> +       if (IS_ERR(opp_table))
> +               return opp_table;
>
>         /*
>          * If the genpd's OPP table isn't already initialized, parsing of the
> @@ -2153,8 +2162,8 @@ int dev_pm_opp_add(struct device *dev, unsigned long freq, unsigned long u_volt)
>         int ret;
>
>         opp_table = dev_pm_opp_get_opp_table(dev);
> -       if (!opp_table)
> -               return -ENOMEM;
> +       if (IS_ERR(opp_table))
> +               return PTR_ERR(opp_table);
>
>         /* Fix regulator count for dynamic OPPs */
>         opp_table->regulator_count = 1;
> diff --git a/drivers/opp/of.c b/drivers/opp/of.c
> index 7d9d4455a59e..e39ddcc779af 100644
> --- a/drivers/opp/of.c
> +++ b/drivers/opp/of.c
> @@ -947,8 +947,8 @@ int dev_pm_opp_of_add_table(struct device *dev)
>         int ret;
>
>         opp_table = dev_pm_opp_get_opp_table_indexed(dev, 0);
> -       if (!opp_table)
> -               return -ENOMEM;
> +       if (IS_ERR(opp_table))
> +               return PTR_ERR(opp_table);
>
>         /*
>          * OPPs have two version of bindings now. Also try the old (v1)
> @@ -1002,8 +1002,8 @@ int dev_pm_opp_of_add_table_indexed(struct device *dev, int index)
>         }
>
>         opp_table = dev_pm_opp_get_opp_table_indexed(dev, index);
> -       if (!opp_table)
> -               return -ENOMEM;
> +       if (IS_ERR(opp_table))
> +               return PTR_ERR(opp_table);
>
>         ret = _of_add_opp_table_v2(dev, opp_table);
>         if (ret)
> diff --git a/drivers/soc/samsung/exynos-asv.c b/drivers/soc/samsung/exynos-asv.c
> index 30bb7b7cc769..8abf4dfaa5c5 100644
> --- a/drivers/soc/samsung/exynos-asv.c
> +++ b/drivers/soc/samsung/exynos-asv.c
> @@ -93,7 +93,7 @@ static int exynos_asv_update_opps(struct exynos_asv *asv)
>                         continue;
>
>                 opp_table = dev_pm_opp_get_opp_table(cpu);
> -               if (IS_ERR_OR_NULL(opp_table))
> +               if (IS_ERR(opp_table))
>                         continue;
>
>                 if (!last_opp_table || opp_table != last_opp_table) {
> --
> 2.25.0.rc1.19.g042ed3e048af
>