Re: [PATCH] opp: Reinitialize the list_kref before adding the static OPPs again

From: Viresh Kumar
Date: Mon Nov 11 2019 - 06:31:28 EST


On 11-11-19, 13:51, Viresh Kumar wrote:
> On 30-10-19, 07:33, Stephen Boyd wrote:
> > I agree a simple refcount_t makes more sense here instead of using a
> > kref. That would be clearer.
>
> I was using kref as I wanted to call the cleanup routine when kref
> reaches 0. A refcount_t will have the same problem as the warning in
> this came from refcount mechanism only (which is used by kref). You
> can't increment a refcount_t if it is zero :)
>
> Any other suggestions other than local counting ?

i.e. something like this, untested.

---
drivers/opp/core.c | 26 ++++++++------------------
drivers/opp/of.c | 14 +++++---------
drivers/opp/opp.h | 6 ++----
3 files changed, 15 insertions(+), 31 deletions(-)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 467b2348a289..ea1d89177511 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -988,7 +988,6 @@ static struct opp_table *_allocate_opp_table(struct device *dev, int index)
BLOCKING_INIT_NOTIFIER_HEAD(&opp_table->head);
INIT_LIST_HEAD(&opp_table->opp_list);
kref_init(&opp_table->kref);
- kref_init(&opp_table->list_kref);

/* Secure the device table modification */
list_add(&opp_table->node, &opp_tables);
@@ -1076,27 +1075,18 @@ static void _opp_remove_all_static(struct opp_table *opp_table)
{
struct dev_pm_opp *opp, *tmp;

+ mutex_lock(&opp_table->lock);
+
+ if (!opp_table->parsed_static_opps || --opp_table->parsed_static_opps)
+ goto unlock;
+
list_for_each_entry_safe(opp, tmp, &opp_table->opp_list, node) {
if (!opp->dynamic)
dev_pm_opp_put(opp);
}

- opp_table->parsed_static_opps = false;
-}
-
-static void _opp_table_list_kref_release(struct kref *kref)
-{
- struct opp_table *opp_table = container_of(kref, struct opp_table,
- list_kref);
-
- _opp_remove_all_static(opp_table);
- mutex_unlock(&opp_table_lock);
-}
-
-void _put_opp_list_kref(struct opp_table *opp_table)
-{
- kref_put_mutex(&opp_table->list_kref, _opp_table_list_kref_release,
- &opp_table_lock);
+unlock:
+ mutex_unlock(&opp_table->lock);
}

void dev_pm_opp_put_opp_table(struct opp_table *opp_table)
@@ -2276,7 +2266,7 @@ void _dev_pm_opp_find_and_remove_table(struct device *dev)
return;
}

- _put_opp_list_kref(opp_table);
+ _opp_remove_all_static(opp_table);

/* Drop reference taken by _find_opp_table() */
dev_pm_opp_put_opp_table(opp_table);
diff --git a/drivers/opp/of.c b/drivers/opp/of.c
index 1cbb58240b80..2c433e9f9223 100644
--- a/drivers/opp/of.c
+++ b/drivers/opp/of.c
@@ -658,17 +658,15 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
struct dev_pm_opp *opp;

/* OPP table is already initialized for the device */
+ mutex_lock(&opp_table->lock);
if (opp_table->parsed_static_opps) {
- kref_get(&opp_table->list_kref);
+ opp_table->parsed_static_opps++;
+ mutex_unlock(&opp_table->lock);
return 0;
}

- /*
- * Re-initialize list_kref every time we add static OPPs to the OPP
- * table as the reference count may be 0 after the last tie static OPPs
- * were removed.
- */
- kref_init(&opp_table->list_kref);
+ opp_table->parsed_static_opps = 1;
+ mutex_unlock(&opp_table->lock);

/* We have opp-table node now, iterate over it and add OPPs */
for_each_available_child_of_node(opp_table->np, np) {
@@ -701,8 +699,6 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
if (pstate_count)
opp_table->genpd_performance_state = true;

- opp_table->parsed_static_opps = true;
-
return 0;
}

diff --git a/drivers/opp/opp.h b/drivers/opp/opp.h
index 51ad942d1b6b..4e69b855a6a0 100644
--- a/drivers/opp/opp.h
+++ b/drivers/opp/opp.h
@@ -127,11 +127,10 @@ enum opp_table_access {
* @dev_list: list of devices that share these OPPs
* @opp_list: table of opps
* @kref: for reference count of the table.
- * @list_kref: for reference count of the OPP list.
* @lock: mutex protecting the opp_list and dev_list.
* @np: struct device_node pointer for opp's DT node.
* @clock_latency_ns_max: Max clock latency in nanoseconds.
- * @parsed_static_opps: True if OPPs are initialized from DT.
+ * @parsed_static_opps: Count of devices for which OPPs are initialized from DT.
* @shared_opp: OPP is shared between multiple devices.
* @suspend_opp: Pointer to OPP to be used during device suspend.
* @genpd_virt_dev_lock: Mutex protecting the genpd virtual device pointers.
@@ -167,7 +166,6 @@ struct opp_table {
struct list_head dev_list;
struct list_head opp_list;
struct kref kref;
- struct kref list_kref;
struct mutex lock;

struct device_node *np;
@@ -176,7 +174,7 @@ struct opp_table {
/* For backward compatibility with v1 bindings */
unsigned int voltage_tolerance_v1;

- bool parsed_static_opps;
+ unsigned int parsed_static_opps;
enum opp_table_access shared_opp;
struct dev_pm_opp *suspend_opp;

--
viresh