Re: [PATCH V3 1/2] PM / OPP: Parse 'opp-supported-hw' binding

[Lee Jones <lee.jones@linaro.org>]

On 9 December 2015 at 02:31, Viresh Kumar <viresh.kumar@linaro.org> wrote:
> OPP bindings allow a platform to enable OPPs based on the version of the
> hardware they are used for.
>
> Add support to the OPP-core to parse these bindings, by introducing
> dev_pm_opp_{set|put}_supported_hw() APIs.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>  drivers/base/power/opp/core.c | 148 ++++++++++++++++++++++++++++++++++++++++++
>  drivers/base/power/opp/opp.h  |   5 ++
>  include/linux/pm_opp.h        |  13 ++++
>  3 files changed, 166 insertions(+)

Tested-by: Lee Jones <lee.jones@linaro.org>

> diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
> index 6aa172be6e8e..55cf1a99b532 100644
> --- a/drivers/base/power/opp/core.c
> +++ b/drivers/base/power/opp/core.c
> @@ -559,6 +559,9 @@ static void _remove_device_opp(struct device_opp *dev_opp)
>         if (!list_empty(&dev_opp->opp_list))
>                 return;
>
> +       if (dev_opp->supported_hw)
> +               return;
> +
>         list_dev = list_first_entry(&dev_opp->dev_list, struct device_list_opp,
>                                     node);
>
> @@ -834,6 +837,145 @@ static int opp_parse_supplies(struct dev_pm_opp *opp, struct device *dev)
>  }
>
>  /**
> + * dev_pm_opp_set_supported_hw() - Set supported platforms
> + * @dev: Device for which supported-hw has to be set.
> + * @versions: Array of hierarchy of versions to match.
> + * @count: Number of elements in the array.
> + *
> + * This is required only for the V2 bindings, and it enables a platform to
> + * specify the hierarchy of versions it supports. OPP layer will then enable
> + * OPPs, which are available for those versions, based on its 'opp-supported-hw'
> + * property.
> + *
> + * Locking: The internal device_opp and opp structures are RCU protected.
> + * Hence this function internally uses RCU updater strategy with mutex locks
> + * to keep the integrity of the internal data structures. Callers should ensure
> + * that this function is *NOT* called under RCU protection or in contexts where
> + * mutex cannot be locked.
> + */
> +int dev_pm_opp_set_supported_hw(struct device *dev, const u32 *versions,
> +                               unsigned int count)
> +{
> +       struct device_opp *dev_opp;
> +       int ret = 0;
> +
> +       /* Hold our list modification lock here */
> +       mutex_lock(&dev_opp_list_lock);
> +
> +       dev_opp = _add_device_opp(dev);
> +       if (!dev_opp) {
> +               ret = -ENOMEM;
> +               goto unlock;
> +       }
> +
> +       /* Make sure there are no concurrent readers while updating dev_opp */
> +       WARN_ON(!list_empty(&dev_opp->opp_list));
> +
> +       /* Do we already have a version hierarchy associated with dev_opp? */
> +       if (dev_opp->supported_hw) {
> +               dev_err(dev, "%s: Already have supported hardware list\n",
> +                       __func__);
> +               ret = -EBUSY;
> +               goto err;
> +       }
> +
> +       dev_opp->supported_hw = kmemdup(versions, count * sizeof(*versions),
> +                                       GFP_KERNEL);
> +       if (!dev_opp->supported_hw) {
> +               ret = -ENOMEM;
> +               goto err;
> +       }
> +
> +       dev_opp->supported_hw_count = count;
> +       mutex_unlock(&dev_opp_list_lock);
> +       return 0;
> +
> +err:
> +       _remove_device_opp(dev_opp);
> +unlock:
> +       mutex_unlock(&dev_opp_list_lock);
> +
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_opp_set_supported_hw);
> +
> +/**
> + * dev_pm_opp_put_supported_hw() - Releases resources blocked for supported hw
> + * @dev: Device for which supported-hw has to be set.
> + *
> + * This is required only for the V2 bindings, and is called for a matching
> + * dev_pm_opp_set_supported_hw(). Until this is called, the device_opp structure
> + * will not be freed.
> + *
> + * Locking: The internal device_opp and opp structures are RCU protected.
> + * Hence this function internally uses RCU updater strategy with mutex locks
> + * to keep the integrity of the internal data structures. Callers should ensure
> + * that this function is *NOT* called under RCU protection or in contexts where
> + * mutex cannot be locked.
> + */
> +void dev_pm_opp_put_supported_hw(struct device *dev)
> +{
> +       struct device_opp *dev_opp;
> +
> +       /* Hold our list modification lock here */
> +       mutex_lock(&dev_opp_list_lock);
> +
> +       /* Check for existing list for 'dev' first */
> +       dev_opp = _find_device_opp(dev);
> +       if (IS_ERR(dev_opp)) {
> +               dev_err(dev, "Failed to find dev_opp: %ld\n", PTR_ERR(dev_opp));
> +               goto unlock;
> +       }
> +
> +       /* Make sure there are no concurrent readers while updating dev_opp */
> +       WARN_ON(!list_empty(&dev_opp->opp_list));
> +
> +       if (!dev_opp->supported_hw) {
> +               dev_err(dev, "%s: Doesn't have supported hardware list\n",
> +                       __func__);
> +               goto unlock;
> +       }
> +
> +       kfree(dev_opp->supported_hw);
> +       dev_opp->supported_hw = NULL;
> +       dev_opp->supported_hw_count = 0;
> +
> +       /* Try freeing device_opp if this was the last blocking resource */
> +       _remove_device_opp(dev_opp);
> +
> +unlock:
> +       mutex_unlock(&dev_opp_list_lock);
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_opp_put_supported_hw);
> +
> +static bool _opp_is_supported(struct device *dev, struct device_opp *dev_opp,
> +                             struct device_node *np)
> +{
> +       unsigned int count = dev_opp->supported_hw_count;
> +       u32 version;
> +       int ret;
> +
> +       if (!dev_opp->supported_hw)
> +               return true;
> +
> +       while (count--) {
> +               ret = of_property_read_u32_index(np, "opp-supported-hw", count,
> +                                                &version);
> +               if (ret) {
> +                       dev_warn(dev, "%s: failed to read opp-supported-hw property at index %d: %d\n",
> +                                __func__, count, ret);
> +                       return false;
> +               }
> +
> +               /* Both of these are bitwise masks of the versions */
> +               if (!(version & dev_opp->supported_hw[count]))
> +                       return false;
> +       }
> +
> +       return true;
> +}
> +
> +/**
>   * _opp_add_static_v2() - Allocate static OPPs (As per 'v2' DT bindings)
>   * @dev:       device for which we do this operation
>   * @np:                device node
> @@ -879,6 +1021,12 @@ static int _opp_add_static_v2(struct device *dev, struct device_node *np)
>                 goto free_opp;
>         }
>
> +       /* Check if the OPP supports hardware's hierarchy of versions or not */
> +       if (!_opp_is_supported(dev, dev_opp, np)) {
> +               dev_dbg(dev, "OPP not supported by hardware: %llu\n", rate);
> +               goto free_opp;
> +       }
> +
>         /*
>          * Rate is defined as an unsigned long in clk API, and so casting
>          * explicitly to its type. Must be fixed once rate is 64 bit
> diff --git a/drivers/base/power/opp/opp.h b/drivers/base/power/opp/opp.h
> index b8880c7f8be1..70f4564a6ab9 100644
> --- a/drivers/base/power/opp/opp.h
> +++ b/drivers/base/power/opp/opp.h
> @@ -129,6 +129,8 @@ struct device_list_opp {
>   * @clock_latency_ns_max: Max clock latency in nanoseconds.
>   * @shared_opp: OPP is shared between multiple devices.
>   * @suspend_opp: Pointer to OPP to be used during device suspend.
> + * @supported_hw: Array of version number to support.
> + * @supported_hw_count: Number of elements in supported_hw array.
>   * @dentry:    debugfs dentry pointer of the real device directory (not links).
>   * @dentry_name: Name of the real dentry.
>   *
> @@ -153,6 +155,9 @@ struct device_opp {
>         bool shared_opp;
>         struct dev_pm_opp *suspend_opp;
>
> +       unsigned int *supported_hw;
> +       unsigned int supported_hw_count;
> +
>  #ifdef CONFIG_DEBUG_FS
>         struct dentry *dentry;
>         char dentry_name[NAME_MAX];
> diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
> index 9a2e50337af9..3a85110242f0 100644
> --- a/include/linux/pm_opp.h
> +++ b/include/linux/pm_opp.h
> @@ -55,6 +55,9 @@ int dev_pm_opp_enable(struct device *dev, unsigned long freq);
>  int dev_pm_opp_disable(struct device *dev, unsigned long freq);
>
>  struct srcu_notifier_head *dev_pm_opp_get_notifier(struct device *dev);
> +int dev_pm_opp_set_supported_hw(struct device *dev, const u32 *versions,
> +                               unsigned int count);
> +void dev_pm_opp_put_supported_hw(struct device *dev);
>  #else
>  static inline unsigned long dev_pm_opp_get_voltage(struct dev_pm_opp *opp)
>  {
> @@ -129,6 +132,16 @@ static inline struct srcu_notifier_head *dev_pm_opp_get_notifier(
>  {
>         return ERR_PTR(-EINVAL);
>  }
> +
> +static inline int dev_pm_opp_set_supported_hw(struct device *dev,
> +                                             const u32 *versions,
> +                                             unsigned int count)
> +{
> +       return -EINVAL;
> +}
> +
> +static inline void dev_pm_opp_put_supported_hw(struct device *dev) {}
> +
>  #endif         /* CONFIG_PM_OPP */
>
>  #if defined(CONFIG_PM_OPP) && defined(CONFIG_OF)
> --
> 2.6.2.198.g614a2ac
>
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-- 
Lee Jones
Linaro ST Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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