Re: [PATCH 2/2] opp: Manage empty OPP tables with clk handle

[Viresh Kumar]

On 03-07-19, 14:41, Rajendra Nayak wrote:
> []..
> > 
> > Explain the rationale behind this code here in a comment.
> > 
> > > +	if (!_get_opp_count(opp_table)) {
> > > +		ret = _generic_set_opp_clk_only(dev, clk, freq);
> > > +		goto put_opp_table;
> > > +	}
> > > +
> > >   	temp_freq = old_freq;
> > >   	old_opp = _find_freq_ceil(opp_table, &temp_freq);
> > >   	if (IS_ERR(old_opp)) {
> > 
> > Also, rebase over the OPP branch please:
> 
> thanks, I will fix/rebase and repost,
> in the meantime while I was testing this a little more I realized I also need
> something like the change below to avoid a refcount mismatch WARN when empty OPP
> table is removed using dev_pm_opp_of_remove_table()
> 
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index fa7d4d6d37b3..20128a88baf2 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -2118,7 +2118,8 @@ void _dev_pm_opp_find_and_remove_table(struct device *dev)
>                 return;
>         }
> -       _put_opp_list_kref(opp_table);
> +       if (_get_opp_count(opp_table))
> +               _put_opp_list_kref(opp_table);
>         /* Drop reference taken by _find_opp_table() */
>         dev_pm_opp_put_opp_table(opp_table);
> 
> Does this look like a good way to fix it?

No. If an OPP table only has dynamic OPPs, this will still generate
warning. Below is the fix I would suggest. Please test it, I haven't
tested it at all :)

-- 
viresh

-------------------------8<-------------------------
From: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Date: Wed, 3 Jul 2019 15:03:14 +0530
Subject: [PATCH] opp: Don't decrement uninitialized list_kref

The list_kref was added for static OPPs and to track their users. The
kref is initialized while the static OPPs are added, but removed
unconditionally even if the static OPPs were never added. This causes
refcount mismatch warnings currently.

Fix that by always initializing the kref when the OPP table is first
initialized. The refcount is later incremented only for the second user
onwards.

Fixes: d0e8ae6c26da ("OPP: Create separate kref for static OPPs list")
Reported-by: Rajendra Nayak <rnayak@xxxxxxxxxxxxxx>
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
 drivers/opp/core.c |  1 +
 drivers/opp/of.c   | 21 ++++-----------------
 2 files changed, 5 insertions(+), 17 deletions(-)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 89ec6aa220cf..2958cc7bbb58 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -943,6 +943,7 @@ 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);
diff --git a/drivers/opp/of.c b/drivers/opp/of.c
index a637f30552a3..bf62b357437c 100644
--- a/drivers/opp/of.c
+++ b/drivers/opp/of.c
@@ -665,8 +665,6 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
 		return 0;
 	}
 
-	kref_init(&opp_table->list_kref);
-
 	/* We have opp-table node now, iterate over it and add OPPs */
 	for_each_available_child_of_node(opp_table->np, np) {
 		opp = _opp_add_static_v2(opp_table, dev, np);
@@ -675,17 +673,15 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
 			dev_err(dev, "%s: Failed to add OPP, %d\n", __func__,
 				ret);
 			of_node_put(np);
-			goto put_list_kref;
+			return ret;
 		} else if (opp) {
 			count++;
 		}
 	}
 
 	/* There should be one of more OPP defined */
-	if (WARN_ON(!count)) {
-		ret = -ENOENT;
-		goto put_list_kref;
-	}
+	if (WARN_ON(!count))
+		return -ENOENT;
 
 	list_for_each_entry(opp, &opp_table->opp_list, node)
 		pstate_count += !!opp->pstate;
@@ -694,8 +690,7 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
 	if (pstate_count && pstate_count != count) {
 		dev_err(dev, "Not all nodes have performance state set (%d: %d)\n",
 			count, pstate_count);
-		ret = -ENOENT;
-		goto put_list_kref;
+		return -ENOENT;
 	}
 
 	if (pstate_count)
@@ -704,11 +699,6 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
 	opp_table->parsed_static_opps = true;
 
 	return 0;
-
-put_list_kref:
-	_put_opp_list_kref(opp_table);
-
-	return ret;
 }
 
 /* Initializes OPP tables based on old-deprecated bindings */
@@ -734,8 +724,6 @@ static int _of_add_opp_table_v1(struct device *dev, struct opp_table *opp_table)
 		return -EINVAL;
 	}
 
-	kref_init(&opp_table->list_kref);
-
 	val = prop->value;
 	while (nr) {
 		unsigned long freq = be32_to_cpup(val++) * 1000;
@@ -745,7 +733,6 @@ static int _of_add_opp_table_v1(struct device *dev, struct opp_table *opp_table)
 		if (ret) {
 			dev_err(dev, "%s: Failed to add OPP %ld (%d)\n",
 				__func__, freq, ret);
-			_put_opp_list_kref(opp_table);
 			return ret;
 		}
 		nr -= 2;