[PATCH v3 10/12] opp: Support set_opp() customization without requiring to use regulators

Dmitry Osipenko
2021-01-18T01:05:22Z

Support set_opp() customization without requiring to use regulators. This
is needed by drivers which want to use dev_pm_opp_set_rate() for changing
rates of a multiple clocks and don't need to touch regulator.

One example is NVIDIA Tegra30/114 SoCs which have two sibling 3D hardware
units which should be use to the same clock rate, meanwhile voltage
scaling is done using a power domain. In this case OPP table doesn't have
a regulator, causing a NULL dereference in _set_opp_custom().

Tested-by: Peter Geis <pgwipeout@gmail.com>
Tested-by: Nicolas Chauvet <kwizart@gmail.com>
Tested-by: Matt Merhar <mattmerhar@protonmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
drivers/opp/core.c | 46 +++++++++++++++++++++++++++++++++++-------
include/linux/pm_opp.h | 3 +++
2 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 49419ab9fbb4..7726c4c40b53 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -829,16 +829,21 @@ static int _set_opp_custom(const struct opp_table *opp_table,
struct dev_pm_opp_supply *new_supply)
{
struct dev_pm_set_opp_data *data;
- int size;
+ int size, count;
+
+ if (opp_table->regulators)
+ count = opp_table->regulator_count;
+ else
+ count = 0;

data = opp_table->set_opp_data;
data->regulators = opp_table->regulators;
- data->regulator_count = opp_table->regulator_count;
+ data->regulator_count = count;
data->clk = opp_table->clk;
data->dev = dev;

data->old_opp.rate = old_freq;
- size = sizeof(*old_supply) * opp_table->regulator_count;
+ size = sizeof(*old_supply) * count;
if (!old_supply)
memset(data->old_opp.supplies, 0, size);
else
@@ -1860,8 +1865,14 @@ static int _allocate_set_opp_data(struct opp_table *opp_table)
struct dev_pm_set_opp_data *data;
int len, count = opp_table->regulator_count;

- if (WARN_ON(!opp_table->regulators))
- return -EINVAL;
+ /* just bump the refcount if already allocated */
+ if (opp_table->set_opp_data) {
+ kref_get(&opp_table->set_opp_data->kref);
+ return 0;
+ }
+
+ /* allocate maximum number of regulators, for simplicity */
+ count = max(count, 1);

/* space for set_opp_data */
len = sizeof(*data);
@@ -1873,6 +1884,7 @@ static int _allocate_set_opp_data(struct opp_table *opp_table)
if (!data)
return -ENOMEM;

+ kref_init(&data->kref);
data->old_opp.supplies = (void *)(data + 1);
data->new_opp.supplies = data->old_opp.supplies + count;

@@ -1881,10 +1893,17 @@ static int _allocate_set_opp_data(struct opp_table *opp_table)
return 0;
}

+static void _release_set_opp_data(struct kref *kref)
+{
+ kfree(container_of(kref, struct dev_pm_set_opp_data, kref));
+}
+
static void _free_set_opp_data(struct opp_table *opp_table)
{
- kfree(opp_table->set_opp_data);
- opp_table->set_opp_data = NULL;
+ struct dev_pm_set_opp_data *data = opp_table->set_opp_data;
+
+ if (kref_put(&data->kref, _release_set_opp_data))
+ opp_table->set_opp_data = NULL;
}

/**
@@ -2182,6 +2201,7 @@ struct opp_table *dev_pm_opp_register_set_opp_helper(struct device *dev,
int (*set_opp)(struct dev_pm_set_opp_data *data))
{
struct opp_table *opp_table;
+ int ret;

if (!set_opp)
return ERR_PTR(-EINVAL);
@@ -2196,11 +2216,21 @@ struct opp_table *dev_pm_opp_register_set_opp_helper(struct device *dev,
return ERR_PTR(-EBUSY);
}

+ /* Allocate block to pass to set_opp() routines */
+ ret = _allocate_set_opp_data(opp_table);
+ if (ret)
+ goto err;
+
/* Another CPU that shares the OPP table has set the helper ? */
if (!opp_table->set_opp)
opp_table->set_opp = set_opp;

return opp_table;
+
+err:
+ dev_pm_opp_put_opp_table(opp_table);
+
+ return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(dev_pm_opp_register_set_opp_helper);

@@ -2219,6 +2249,8 @@ void dev_pm_opp_unregister_set_opp_helper(struct opp_table *opp_table)
/* Make sure there are no concurrent readers while updating opp_table */
WARN_ON(!list_empty(&opp_table->opp_list));

+ _free_set_opp_data(opp_table);
+
opp_table->set_opp = NULL;
dev_pm_opp_put_opp_table(opp_table);
}
diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
index eefd0b15890c..c98fd2add563 100644
--- a/include/linux/pm_opp.h
+++ b/include/linux/pm_opp.h
@@ -13,6 +13,7 @@

#include <linux/energy_model.h>
#include <linux/err.h>
+#include <linux/kref.h>
#include <linux/notifier.h>

struct clk;
@@ -74,6 +75,7 @@ struct dev_pm_opp_info {
* @regulator_count: Number of regulators
* @clk: Pointer to clk
* @dev: Pointer to the struct device
+ * @kref: Reference counter
*
* This structure contains all information required for setting an OPP.
*/
@@ -85,6 +87,7 @@ struct dev_pm_set_opp_data {
unsigned int regulator_count;
struct clk *clk;
struct device *dev;
+ struct kref kref;
};

#if defined(CONFIG_PM_OPP)
--
2.29.2