diff mbox series

[V3,02/20] OPP: Make dev_pm_opp_set_regulators() accept NULL terminated list

Message ID 9730e011004b7526e79c6f409f5147fb235b414a.1656935522.git.viresh.kumar@linaro.org (mailing list archive)
State New
Headers show
Series OPP: Add new configuration interface: dev_pm_opp_set_config() | expand

Commit Message

Viresh Kumar July 4, 2022, 12:07 p.m. UTC
Make dev_pm_opp_set_regulators() accept a NULL terminated list of names
instead of making the callers keep the two parameters in sync, which
creates an opportunity for bugs to get in.

Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/cpufreq/cpufreq-dt.c                |  9 ++++-----
 drivers/cpufreq/ti-cpufreq.c                |  7 +++----
 drivers/devfreq/exynos-bus.c                |  4 ++--
 drivers/gpu/drm/lima/lima_devfreq.c         |  3 ++-
 drivers/gpu/drm/panfrost/panfrost_devfreq.c |  4 ++--
 drivers/opp/core.c                          | 18 ++++++++++++------
 drivers/soc/tegra/pmc.c                     |  4 ++--
 include/linux/pm_opp.h                      |  9 ++++-----
 8 files changed, 31 insertions(+), 27 deletions(-)

Comments

Steven Price July 4, 2022, 2:35 p.m. UTC | #1
On 04/07/2022 13:07, Viresh Kumar wrote:
> Make dev_pm_opp_set_regulators() accept a NULL terminated list of names
> instead of making the callers keep the two parameters in sync, which
> creates an opportunity for bugs to get in.
> 
> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>  drivers/cpufreq/cpufreq-dt.c                |  9 ++++-----
>  drivers/cpufreq/ti-cpufreq.c                |  7 +++----
>  drivers/devfreq/exynos-bus.c                |  4 ++--
>  drivers/gpu/drm/lima/lima_devfreq.c         |  3 ++-
>  drivers/gpu/drm/panfrost/panfrost_devfreq.c |  4 ++--
>  drivers/opp/core.c                          | 18 ++++++++++++------
>  drivers/soc/tegra/pmc.c                     |  4 ++--
>  include/linux/pm_opp.h                      |  9 ++++-----
>  8 files changed, 31 insertions(+), 27 deletions(-)
> 
[...]
> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> index 194af7f607a6..12784f349550 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> @@ -91,6 +91,7 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
>  	struct devfreq *devfreq;
>  	struct thermal_cooling_device *cooling;
>  	struct panfrost_devfreq *pfdevfreq = &pfdev->pfdevfreq;
> +	const char *supplies[] = { pfdev->comp->supply_names[0], NULL };
>  
>  	if (pfdev->comp->num_supplies > 1) {
>  		/*
> @@ -101,8 +102,7 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
>  		return 0;
>  	}
>  
> -	ret = devm_pm_opp_set_regulators(dev, pfdev->comp->supply_names,
> -					 pfdev->comp->num_supplies);
> +	ret = devm_pm_opp_set_regulators(dev, supplies);
>  	if (ret) {
>  		/* Continue if the optional regulator is missing */
>  		if (ret != -ENODEV) {

I have to say the 'new improved' list ending with NULL approach doesn't
work out so well for Panfrost. We already have to have a separate
'num_supplies' variable for devm_regulator_bulk_get() /
regulator_bulk_{en,dis}able(), so the keeping everything in sync
argument is lost here.

I would suggest added the NULL on the end of the lists in panfrost_drv.c
but then it would break the use of ARRAY_SIZE() to automagically keep
the length correct...

For now the approach isn't too bad because Panfrost doesn't yet support
enabling devfreq with more than one supply. But that array isn't going
to work so nicely when that restriction is removed.

The only sane way I can see of handling this in Panfrost would be
replicating the loop to count the supplies in the Panfrost code which
would allow dropping num_supplies from struct panfrost_compatible and
then supply_names in the same struct could be NULL terminated ready for
devm_pm_opp_set_regulators().

Steve

> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index e166bfe5fc90..4e4593957ec5 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -2105,13 +2105,20 @@ EXPORT_SYMBOL_GPL(dev_pm_opp_put_prop_name);
>   * This must be called before any OPPs are initialized for the device.
>   */
>  struct opp_table *dev_pm_opp_set_regulators(struct device *dev,
> -					    const char * const names[],
> -					    unsigned int count)
> +					    const char * const names[])
>  {
>  	struct dev_pm_opp_supply *supplies;
> +	const char * const *temp = names;
>  	struct opp_table *opp_table;
>  	struct regulator *reg;
> -	int ret, i;
> +	int count = 0, ret, i;
> +
> +	/* Count number of regulators */
> +	while (*temp++)
> +		count++;
> +
> +	if (!count)
> +		return ERR_PTR(-EINVAL);
>  
>  	opp_table = _add_opp_table(dev, false);
>  	if (IS_ERR(opp_table))
> @@ -2236,12 +2243,11 @@ static void devm_pm_opp_regulators_release(void *data)
>   * Return: 0 on success and errorno otherwise.
>   */
>  int devm_pm_opp_set_regulators(struct device *dev,
> -			       const char * const names[],
> -			       unsigned int count)
> +			       const char * const names[])
>  {
>  	struct opp_table *opp_table;
>  
> -	opp_table = dev_pm_opp_set_regulators(dev, names, count);
> +	opp_table = dev_pm_opp_set_regulators(dev, names);
>  	if (IS_ERR(opp_table))
>  		return PTR_ERR(opp_table);
>  
> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
> index 5611d14d3ba2..6a4b8f7e7948 100644
> --- a/drivers/soc/tegra/pmc.c
> +++ b/drivers/soc/tegra/pmc.c
> @@ -1384,7 +1384,7 @@ tegra_pmc_core_pd_opp_to_performance_state(struct generic_pm_domain *genpd,
>  static int tegra_pmc_core_pd_add(struct tegra_pmc *pmc, struct device_node *np)
>  {
>  	struct generic_pm_domain *genpd;
> -	const char *rname = "core";
> +	const char *rname[] = { "core", NULL};
>  	int err;
>  
>  	genpd = devm_kzalloc(pmc->dev, sizeof(*genpd), GFP_KERNEL);
> @@ -1395,7 +1395,7 @@ static int tegra_pmc_core_pd_add(struct tegra_pmc *pmc, struct device_node *np)
>  	genpd->set_performance_state = tegra_pmc_core_pd_set_performance_state;
>  	genpd->opp_to_performance_state = tegra_pmc_core_pd_opp_to_performance_state;
>  
> -	err = devm_pm_opp_set_regulators(pmc->dev, &rname, 1);
> +	err = devm_pm_opp_set_regulators(pmc->dev, rname);
>  	if (err)
>  		return dev_err_probe(pmc->dev, err,
>  				     "failed to set core OPP regulator\n");
> diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
> index 6708b4ec244d..4c490865d574 100644
> --- a/include/linux/pm_opp.h
> +++ b/include/linux/pm_opp.h
> @@ -159,9 +159,9 @@ void dev_pm_opp_put_supported_hw(struct opp_table *opp_table);
>  int devm_pm_opp_set_supported_hw(struct device *dev, const u32 *versions, unsigned int count);
>  struct opp_table *dev_pm_opp_set_prop_name(struct device *dev, const char *name);
>  void dev_pm_opp_put_prop_name(struct opp_table *opp_table);
> -struct opp_table *dev_pm_opp_set_regulators(struct device *dev, const char * const names[], unsigned int count);
> +struct opp_table *dev_pm_opp_set_regulators(struct device *dev, const char * const names[]);
>  void dev_pm_opp_put_regulators(struct opp_table *opp_table);
> -int devm_pm_opp_set_regulators(struct device *dev, const char * const names[], unsigned int count);
> +int devm_pm_opp_set_regulators(struct device *dev, const char * const names[]);
>  struct opp_table *dev_pm_opp_set_clkname(struct device *dev, const char *name);
>  void dev_pm_opp_put_clkname(struct opp_table *opp_table);
>  int devm_pm_opp_set_clkname(struct device *dev, const char *name);
> @@ -379,7 +379,7 @@ static inline struct opp_table *dev_pm_opp_set_prop_name(struct device *dev, con
>  
>  static inline void dev_pm_opp_put_prop_name(struct opp_table *opp_table) {}
>  
> -static inline struct opp_table *dev_pm_opp_set_regulators(struct device *dev, const char * const names[], unsigned int count)
> +static inline struct opp_table *dev_pm_opp_set_regulators(struct device *dev, const char * const names[])
>  {
>  	return ERR_PTR(-EOPNOTSUPP);
>  }
> @@ -387,8 +387,7 @@ static inline struct opp_table *dev_pm_opp_set_regulators(struct device *dev, co
>  static inline void dev_pm_opp_put_regulators(struct opp_table *opp_table) {}
>  
>  static inline int devm_pm_opp_set_regulators(struct device *dev,
> -					     const char * const names[],
> -					     unsigned int count)
> +					     const char * const names[])
>  {
>  	return -EOPNOTSUPP;
>  }
Viresh Kumar July 5, 2022, 4:34 a.m. UTC | #2
On 04-07-22, 15:35, Steven Price wrote:
> I have to say the 'new improved' list ending with NULL approach doesn't
> work out so well for Panfrost. We already have to have a separate
> 'num_supplies' variable for devm_regulator_bulk_get() /
> regulator_bulk_{en,dis}able(), so the keeping everything in sync
> argument is lost here.
> 
> I would suggest added the NULL on the end of the lists in panfrost_drv.c
> but then it would break the use of ARRAY_SIZE() to automagically keep
> the length correct...

Actually we can still make it work.

> For now the approach isn't too bad because Panfrost doesn't yet support
> enabling devfreq with more than one supply. But that array isn't going
> to work so nicely when that restriction is removed.
> 
> The only sane way I can see of handling this in Panfrost would be
> replicating the loop to count the supplies in the Panfrost code which
> would allow dropping num_supplies from struct panfrost_compatible and
> then supply_names in the same struct could be NULL terminated ready for
> devm_pm_opp_set_regulators().

Or doing this, which will simplify both the cases.

diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
index 7fcbc2a5b6cd..b3b55565b8ef 100644
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
@@ -625,24 +625,29 @@ static int panfrost_remove(struct platform_device *pdev)
        return 0;
 }
 
-static const char * const default_supplies[] = { "mali" };
+/*
+ * The OPP core wants the supply names to be NULL terminated, but we need the
+ * correct num_supplies value for regulator core. Hence, we NULL terminate here
+ * and then initialize num_supplies with ARRAY_SIZE - 1.
+ */
+static const char * const default_supplies[] = { "mali", NULL };
 static const struct panfrost_compatible default_data = {
-       .num_supplies = ARRAY_SIZE(default_supplies),
+       .num_supplies = ARRAY_SIZE(default_supplies) - 1,
        .supply_names = default_supplies,
        .num_pm_domains = 1, /* optional */
        .pm_domain_names = NULL,
 };
 
 static const struct panfrost_compatible amlogic_data = {
-       .num_supplies = ARRAY_SIZE(default_supplies),
+       .num_supplies = ARRAY_SIZE(default_supplies) - 1,
        .supply_names = default_supplies,
        .vendor_quirk = panfrost_gpu_amlogic_quirk,
 };
 
-static const char * const mediatek_mt8183_supplies[] = { "mali", "sram" };
+static const char * const mediatek_mt8183_supplies[] = { "mali", "sram", NULL };
 static const char * const mediatek_mt8183_pm_domains[] = { "core0", "core1", "core2" };
 static const struct panfrost_compatible mediatek_mt8183_data = {
-       .num_supplies = ARRAY_SIZE(mediatek_mt8183_supplies),
+       .num_supplies = ARRAY_SIZE(mediatek_mt8183_supplies) - 1,
        .supply_names = mediatek_mt8183_supplies,
        .num_pm_domains = ARRAY_SIZE(mediatek_mt8183_pm_domains),
        .pm_domain_names = mediatek_mt8183_pm_domains,
Steven Price July 6, 2022, 8:09 a.m. UTC | #3
On 05/07/2022 05:34, Viresh Kumar wrote:
> On 04-07-22, 15:35, Steven Price wrote:
>> I have to say the 'new improved' list ending with NULL approach doesn't
>> work out so well for Panfrost. We already have to have a separate
>> 'num_supplies' variable for devm_regulator_bulk_get() /
>> regulator_bulk_{en,dis}able(), so the keeping everything in sync
>> argument is lost here.
>>
>> I would suggest added the NULL on the end of the lists in panfrost_drv.c
>> but then it would break the use of ARRAY_SIZE() to automagically keep
>> the length correct...
> 
> Actually we can still make it work.
> 
>> For now the approach isn't too bad because Panfrost doesn't yet support
>> enabling devfreq with more than one supply. But that array isn't going
>> to work so nicely when that restriction is removed.
>>
>> The only sane way I can see of handling this in Panfrost would be
>> replicating the loop to count the supplies in the Panfrost code which
>> would allow dropping num_supplies from struct panfrost_compatible and
>> then supply_names in the same struct could be NULL terminated ready for
>> devm_pm_opp_set_regulators().
> 
> Or doing this, which will simplify both the cases.

Yes the below works, it's just a bit ugly having the "- 1", and
potentially easy to forgot when adding another. However I don't suppose
it would get far in that case so I think it would be spotted quickly
when adding a new compatible.

It's probably the best solution at the moment.

Thanks,

Steve

> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index 7fcbc2a5b6cd..b3b55565b8ef 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -625,24 +625,29 @@ static int panfrost_remove(struct platform_device *pdev)
>         return 0;
>  }
>  
> -static const char * const default_supplies[] = { "mali" };
> +/*
> + * The OPP core wants the supply names to be NULL terminated, but we need the
> + * correct num_supplies value for regulator core. Hence, we NULL terminate here
> + * and then initialize num_supplies with ARRAY_SIZE - 1.
> + */
> +static const char * const default_supplies[] = { "mali", NULL };
>  static const struct panfrost_compatible default_data = {
> -       .num_supplies = ARRAY_SIZE(default_supplies),
> +       .num_supplies = ARRAY_SIZE(default_supplies) - 1,
>         .supply_names = default_supplies,
>         .num_pm_domains = 1, /* optional */
>         .pm_domain_names = NULL,
>  };
>  
>  static const struct panfrost_compatible amlogic_data = {
> -       .num_supplies = ARRAY_SIZE(default_supplies),
> +       .num_supplies = ARRAY_SIZE(default_supplies) - 1,
>         .supply_names = default_supplies,
>         .vendor_quirk = panfrost_gpu_amlogic_quirk,
>  };
>  
> -static const char * const mediatek_mt8183_supplies[] = { "mali", "sram" };
> +static const char * const mediatek_mt8183_supplies[] = { "mali", "sram", NULL };
>  static const char * const mediatek_mt8183_pm_domains[] = { "core0", "core1", "core2" };
>  static const struct panfrost_compatible mediatek_mt8183_data = {
> -       .num_supplies = ARRAY_SIZE(mediatek_mt8183_supplies),
> +       .num_supplies = ARRAY_SIZE(mediatek_mt8183_supplies) - 1,
>         .supply_names = mediatek_mt8183_supplies,
>         .num_pm_domains = ARRAY_SIZE(mediatek_mt8183_pm_domains),
>         .pm_domain_names = mediatek_mt8183_pm_domains,
>
Chanwoo Choi July 7, 2022, 7:04 p.m. UTC | #4
On 22. 7. 4. 21:07, Viresh Kumar wrote:
> Make dev_pm_opp_set_regulators() accept a NULL terminated list of names
> instead of making the callers keep the two parameters in sync, which
> creates an opportunity for bugs to get in.
> 
> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>  drivers/cpufreq/cpufreq-dt.c                |  9 ++++-----
>  drivers/cpufreq/ti-cpufreq.c                |  7 +++----
>  drivers/devfreq/exynos-bus.c                |  4 ++--
>  drivers/gpu/drm/lima/lima_devfreq.c         |  3 ++-
>  drivers/gpu/drm/panfrost/panfrost_devfreq.c |  4 ++--
>  drivers/opp/core.c                          | 18 ++++++++++++------
>  drivers/soc/tegra/pmc.c                     |  4 ++--
>  include/linux/pm_opp.h                      |  9 ++++-----
>  8 files changed, 31 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
> index 8fcaba541539..be0c19b3ffa5 100644
> --- a/drivers/cpufreq/cpufreq-dt.c
> +++ b/drivers/cpufreq/cpufreq-dt.c
> @@ -193,7 +193,7 @@ static int dt_cpufreq_early_init(struct device *dev, int cpu)
>  	struct private_data *priv;
>  	struct device *cpu_dev;
>  	bool fallback = false;
> -	const char *reg_name;
> +	const char *reg_name[] = { NULL, NULL };
>  	int ret;
>  
>  	/* Check if this CPU is already covered by some other policy */
> @@ -218,10 +218,9 @@ static int dt_cpufreq_early_init(struct device *dev, int cpu)
>  	 * OPP layer will be taking care of regulators now, but it needs to know
>  	 * the name of the regulator first.
>  	 */
> -	reg_name = find_supply_name(cpu_dev);
> -	if (reg_name) {
> -		priv->opp_table = dev_pm_opp_set_regulators(cpu_dev, &reg_name,
> -							    1);
> +	reg_name[0] = find_supply_name(cpu_dev);
> +	if (reg_name[0]) {
> +		priv->opp_table = dev_pm_opp_set_regulators(cpu_dev, reg_name);
>  		if (IS_ERR(priv->opp_table)) {
>  			ret = PTR_ERR(priv->opp_table);
>  			if (ret != -EPROBE_DEFER)
> diff --git a/drivers/cpufreq/ti-cpufreq.c b/drivers/cpufreq/ti-cpufreq.c
> index 8f9fdd864391..560d67a6bef1 100644
> --- a/drivers/cpufreq/ti-cpufreq.c
> +++ b/drivers/cpufreq/ti-cpufreq.c
> @@ -173,7 +173,7 @@ static struct ti_cpufreq_soc_data omap34xx_soc_data = {
>   *    seems to always read as 0).
>   */
>  
> -static const char * const omap3_reg_names[] = {"cpu0", "vbb"};
> +static const char * const omap3_reg_names[] = {"cpu0", "vbb", NULL};
>  
>  static struct ti_cpufreq_soc_data omap36xx_soc_data = {
>  	.reg_names = omap3_reg_names,
> @@ -326,7 +326,7 @@ static int ti_cpufreq_probe(struct platform_device *pdev)
>  	const struct of_device_id *match;
>  	struct opp_table *ti_opp_table;
>  	struct ti_cpufreq_data *opp_data;
> -	const char * const default_reg_names[] = {"vdd", "vbb"};
> +	const char * const default_reg_names[] = {"vdd", "vbb", NULL};
>  	int ret;
>  
>  	match = dev_get_platdata(&pdev->dev);
> @@ -387,8 +387,7 @@ static int ti_cpufreq_probe(struct platform_device *pdev)
>  		if (opp_data->soc_data->reg_names)
>  			reg_names = opp_data->soc_data->reg_names;
>  		ti_opp_table = dev_pm_opp_set_regulators(opp_data->cpu_dev,
> -							 reg_names,
> -							 ARRAY_SIZE(default_reg_names));
> +							 reg_names);
>  		if (IS_ERR(ti_opp_table)) {
>  			dev_pm_opp_put_supported_hw(opp_data->opp_table);
>  			ret =  PTR_ERR(ti_opp_table);
> diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
> index e689101abc93..541baff93ee8 100644
> --- a/drivers/devfreq/exynos-bus.c
> +++ b/drivers/devfreq/exynos-bus.c
> @@ -180,10 +180,10 @@ static int exynos_bus_parent_parse_of(struct device_node *np,
>  {
>  	struct device *dev = bus->dev;
>  	struct opp_table *opp_table;
> -	const char *vdd = "vdd";
> +	const char *supplies[] = { "vdd", NULL };
>  	int i, ret, count, size;
>  
> -	opp_table = dev_pm_opp_set_regulators(dev, &vdd, 1);
> +	opp_table = dev_pm_opp_set_regulators(dev, supplies);
>  	if (IS_ERR(opp_table)) {
>  		ret = PTR_ERR(opp_table);
>  		dev_err(dev, "failed to set regulators %d\n", ret);

Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>

(snip)
diff mbox series

Patch

diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
index 8fcaba541539..be0c19b3ffa5 100644
--- a/drivers/cpufreq/cpufreq-dt.c
+++ b/drivers/cpufreq/cpufreq-dt.c
@@ -193,7 +193,7 @@  static int dt_cpufreq_early_init(struct device *dev, int cpu)
 	struct private_data *priv;
 	struct device *cpu_dev;
 	bool fallback = false;
-	const char *reg_name;
+	const char *reg_name[] = { NULL, NULL };
 	int ret;
 
 	/* Check if this CPU is already covered by some other policy */
@@ -218,10 +218,9 @@  static int dt_cpufreq_early_init(struct device *dev, int cpu)
 	 * OPP layer will be taking care of regulators now, but it needs to know
 	 * the name of the regulator first.
 	 */
-	reg_name = find_supply_name(cpu_dev);
-	if (reg_name) {
-		priv->opp_table = dev_pm_opp_set_regulators(cpu_dev, &reg_name,
-							    1);
+	reg_name[0] = find_supply_name(cpu_dev);
+	if (reg_name[0]) {
+		priv->opp_table = dev_pm_opp_set_regulators(cpu_dev, reg_name);
 		if (IS_ERR(priv->opp_table)) {
 			ret = PTR_ERR(priv->opp_table);
 			if (ret != -EPROBE_DEFER)
diff --git a/drivers/cpufreq/ti-cpufreq.c b/drivers/cpufreq/ti-cpufreq.c
index 8f9fdd864391..560d67a6bef1 100644
--- a/drivers/cpufreq/ti-cpufreq.c
+++ b/drivers/cpufreq/ti-cpufreq.c
@@ -173,7 +173,7 @@  static struct ti_cpufreq_soc_data omap34xx_soc_data = {
  *    seems to always read as 0).
  */
 
-static const char * const omap3_reg_names[] = {"cpu0", "vbb"};
+static const char * const omap3_reg_names[] = {"cpu0", "vbb", NULL};
 
 static struct ti_cpufreq_soc_data omap36xx_soc_data = {
 	.reg_names = omap3_reg_names,
@@ -326,7 +326,7 @@  static int ti_cpufreq_probe(struct platform_device *pdev)
 	const struct of_device_id *match;
 	struct opp_table *ti_opp_table;
 	struct ti_cpufreq_data *opp_data;
-	const char * const default_reg_names[] = {"vdd", "vbb"};
+	const char * const default_reg_names[] = {"vdd", "vbb", NULL};
 	int ret;
 
 	match = dev_get_platdata(&pdev->dev);
@@ -387,8 +387,7 @@  static int ti_cpufreq_probe(struct platform_device *pdev)
 		if (opp_data->soc_data->reg_names)
 			reg_names = opp_data->soc_data->reg_names;
 		ti_opp_table = dev_pm_opp_set_regulators(opp_data->cpu_dev,
-							 reg_names,
-							 ARRAY_SIZE(default_reg_names));
+							 reg_names);
 		if (IS_ERR(ti_opp_table)) {
 			dev_pm_opp_put_supported_hw(opp_data->opp_table);
 			ret =  PTR_ERR(ti_opp_table);
diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
index e689101abc93..541baff93ee8 100644
--- a/drivers/devfreq/exynos-bus.c
+++ b/drivers/devfreq/exynos-bus.c
@@ -180,10 +180,10 @@  static int exynos_bus_parent_parse_of(struct device_node *np,
 {
 	struct device *dev = bus->dev;
 	struct opp_table *opp_table;
-	const char *vdd = "vdd";
+	const char *supplies[] = { "vdd", NULL };
 	int i, ret, count, size;
 
-	opp_table = dev_pm_opp_set_regulators(dev, &vdd, 1);
+	opp_table = dev_pm_opp_set_regulators(dev, supplies);
 	if (IS_ERR(opp_table)) {
 		ret = PTR_ERR(opp_table);
 		dev_err(dev, "failed to set regulators %d\n", ret);
diff --git a/drivers/gpu/drm/lima/lima_devfreq.c b/drivers/gpu/drm/lima/lima_devfreq.c
index 8989e215dfc9..dc83c5421125 100644
--- a/drivers/gpu/drm/lima/lima_devfreq.c
+++ b/drivers/gpu/drm/lima/lima_devfreq.c
@@ -111,6 +111,7 @@  int lima_devfreq_init(struct lima_device *ldev)
 	struct dev_pm_opp *opp;
 	unsigned long cur_freq;
 	int ret;
+	const char *regulator_names[] = { "mali", NULL };
 
 	if (!device_property_present(dev, "operating-points-v2"))
 		/* Optional, continue without devfreq */
@@ -122,7 +123,7 @@  int lima_devfreq_init(struct lima_device *ldev)
 	if (ret)
 		return ret;
 
-	ret = devm_pm_opp_set_regulators(dev, (const char *[]){ "mali" }, 1);
+	ret = devm_pm_opp_set_regulators(dev, regulator_names);
 	if (ret) {
 		/* Continue if the optional regulator is missing */
 		if (ret != -ENODEV)
diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
index 194af7f607a6..12784f349550 100644
--- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
+++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
@@ -91,6 +91,7 @@  int panfrost_devfreq_init(struct panfrost_device *pfdev)
 	struct devfreq *devfreq;
 	struct thermal_cooling_device *cooling;
 	struct panfrost_devfreq *pfdevfreq = &pfdev->pfdevfreq;
+	const char *supplies[] = { pfdev->comp->supply_names[0], NULL };
 
 	if (pfdev->comp->num_supplies > 1) {
 		/*
@@ -101,8 +102,7 @@  int panfrost_devfreq_init(struct panfrost_device *pfdev)
 		return 0;
 	}
 
-	ret = devm_pm_opp_set_regulators(dev, pfdev->comp->supply_names,
-					 pfdev->comp->num_supplies);
+	ret = devm_pm_opp_set_regulators(dev, supplies);
 	if (ret) {
 		/* Continue if the optional regulator is missing */
 		if (ret != -ENODEV) {
diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index e166bfe5fc90..4e4593957ec5 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -2105,13 +2105,20 @@  EXPORT_SYMBOL_GPL(dev_pm_opp_put_prop_name);
  * This must be called before any OPPs are initialized for the device.
  */
 struct opp_table *dev_pm_opp_set_regulators(struct device *dev,
-					    const char * const names[],
-					    unsigned int count)
+					    const char * const names[])
 {
 	struct dev_pm_opp_supply *supplies;
+	const char * const *temp = names;
 	struct opp_table *opp_table;
 	struct regulator *reg;
-	int ret, i;
+	int count = 0, ret, i;
+
+	/* Count number of regulators */
+	while (*temp++)
+		count++;
+
+	if (!count)
+		return ERR_PTR(-EINVAL);
 
 	opp_table = _add_opp_table(dev, false);
 	if (IS_ERR(opp_table))
@@ -2236,12 +2243,11 @@  static void devm_pm_opp_regulators_release(void *data)
  * Return: 0 on success and errorno otherwise.
  */
 int devm_pm_opp_set_regulators(struct device *dev,
-			       const char * const names[],
-			       unsigned int count)
+			       const char * const names[])
 {
 	struct opp_table *opp_table;
 
-	opp_table = dev_pm_opp_set_regulators(dev, names, count);
+	opp_table = dev_pm_opp_set_regulators(dev, names);
 	if (IS_ERR(opp_table))
 		return PTR_ERR(opp_table);
 
diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
index 5611d14d3ba2..6a4b8f7e7948 100644
--- a/drivers/soc/tegra/pmc.c
+++ b/drivers/soc/tegra/pmc.c
@@ -1384,7 +1384,7 @@  tegra_pmc_core_pd_opp_to_performance_state(struct generic_pm_domain *genpd,
 static int tegra_pmc_core_pd_add(struct tegra_pmc *pmc, struct device_node *np)
 {
 	struct generic_pm_domain *genpd;
-	const char *rname = "core";
+	const char *rname[] = { "core", NULL};
 	int err;
 
 	genpd = devm_kzalloc(pmc->dev, sizeof(*genpd), GFP_KERNEL);
@@ -1395,7 +1395,7 @@  static int tegra_pmc_core_pd_add(struct tegra_pmc *pmc, struct device_node *np)
 	genpd->set_performance_state = tegra_pmc_core_pd_set_performance_state;
 	genpd->opp_to_performance_state = tegra_pmc_core_pd_opp_to_performance_state;
 
-	err = devm_pm_opp_set_regulators(pmc->dev, &rname, 1);
+	err = devm_pm_opp_set_regulators(pmc->dev, rname);
 	if (err)
 		return dev_err_probe(pmc->dev, err,
 				     "failed to set core OPP regulator\n");
diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
index 6708b4ec244d..4c490865d574 100644
--- a/include/linux/pm_opp.h
+++ b/include/linux/pm_opp.h
@@ -159,9 +159,9 @@  void dev_pm_opp_put_supported_hw(struct opp_table *opp_table);
 int devm_pm_opp_set_supported_hw(struct device *dev, const u32 *versions, unsigned int count);
 struct opp_table *dev_pm_opp_set_prop_name(struct device *dev, const char *name);
 void dev_pm_opp_put_prop_name(struct opp_table *opp_table);
-struct opp_table *dev_pm_opp_set_regulators(struct device *dev, const char * const names[], unsigned int count);
+struct opp_table *dev_pm_opp_set_regulators(struct device *dev, const char * const names[]);
 void dev_pm_opp_put_regulators(struct opp_table *opp_table);
-int devm_pm_opp_set_regulators(struct device *dev, const char * const names[], unsigned int count);
+int devm_pm_opp_set_regulators(struct device *dev, const char * const names[]);
 struct opp_table *dev_pm_opp_set_clkname(struct device *dev, const char *name);
 void dev_pm_opp_put_clkname(struct opp_table *opp_table);
 int devm_pm_opp_set_clkname(struct device *dev, const char *name);
@@ -379,7 +379,7 @@  static inline struct opp_table *dev_pm_opp_set_prop_name(struct device *dev, con
 
 static inline void dev_pm_opp_put_prop_name(struct opp_table *opp_table) {}
 
-static inline struct opp_table *dev_pm_opp_set_regulators(struct device *dev, const char * const names[], unsigned int count)
+static inline struct opp_table *dev_pm_opp_set_regulators(struct device *dev, const char * const names[])
 {
 	return ERR_PTR(-EOPNOTSUPP);
 }
@@ -387,8 +387,7 @@  static inline struct opp_table *dev_pm_opp_set_regulators(struct device *dev, co
 static inline void dev_pm_opp_put_regulators(struct opp_table *opp_table) {}
 
 static inline int devm_pm_opp_set_regulators(struct device *dev,
-					     const char * const names[],
-					     unsigned int count)
+					     const char * const names[])
 {
 	return -EOPNOTSUPP;
 }