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SubjectRe: [RFC PATCH 1/2] opp: Allow dev_pm_opp_get_opp_table() to return -EPROBE_DEFER
On Mon, 27 Jul 2020 at 11:31, Stephan Gerhold <stephan@gerhold.net> wrote:
>
> 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@gerhold.net>
> ---
> I wasn't sure if the changes in drivers/base/power/domain.c
> should be made in a separate commit, but they need to be made together
> with the other changes.

I would suggest to move the changes in drivers/base/power/domain.c
into a separate patch, still part of the series, but let it preceed
$subject patch.

>
> Also note that this is RFC because this is just something I got really
> frustrated about. There might be situations where this won't work correctly...?
> ---
> drivers/base/power/domain.c | 28 ++++++++++++++++++-----

The above changes look good to me.

For the below, at a quick look I have no objections, but I am
deferring to Viresh to have a closer look.

Kind regards
Uffe

> drivers/opp/core.c | 45 ++++++++++++++++++++++---------------
> drivers/opp/of.c | 8 +++----
> 3 files changed, 53 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 2cb5e04cf86c..c50f2de952c4 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 +2055,14 @@ 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);
> + if (IS_ERR(genpd->opp_table)) {
> + if (PTR_ERR(genpd->opp_table) != -EPROBE_DEFER)
> + dev_err(&genpd->dev, "Failed to get OPP table: %pe\n",
> + genpd->opp_table);
> +
> + dev_pm_opp_of_remove_table(&genpd->dev);
> + goto unlock;
> + }
> }
>
> ret = genpd_add_provider(np, genpd_xlate_simple, genpd);
> @@ -2111,8 +2119,9 @@ 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 +2130,14 @@ 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);
> + if (IS_ERR(genpd->opp_table)) {
> + if (PTR_ERR(genpd->opp_table) != -EPROBE_DEFER)
> + dev_err(&genpd->dev, "Failed to get OPP table: %pe\n",
> + genpd->opp_table);
> +
> + dev_pm_opp_of_remove_table(&genpd->dev);
> + goto error;
> + }
> }
>
> genpd->provider = &np->fwnode;
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index 9d7fb45b1786..45d24de75e0e 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -1063,7 +1063,7 @@ 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);
> @@ -1074,8 +1074,8 @@ 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);
> @@ -1087,13 +1087,18 @@ static struct opp_table *_allocate_opp_table(struct device *dev, int index)
> if (ret != -EPROBE_DEFER)
> dev_dbg(dev, "%s: Couldn't find clock: %d\n", __func__,
> ret);
> + else
> + goto err;
> }
>
> /* 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);
> @@ -1102,6 +1107,10 @@ 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)
> @@ -1568,8 +1577,8 @@ 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));
> @@ -1627,8 +1636,8 @@ 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));
> @@ -1720,8 +1729,8 @@ 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))) {
> @@ -1830,8 +1839,8 @@ 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))) {
> @@ -1898,8 +1907,8 @@ 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))) {
> @@ -1979,8 +1988,8 @@ 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
> @@ -2150,8 +2159,8 @@ 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 0430290670ab..d8b623cc015a 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)
> --
> 2.27.0
>

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