Re: [PATCH 2/5] clk: notifier handler for dynamic voltage scaling

Francesco Lavra
2013-03-10T10:20:20Z

On 02/28/2013 05:49 AM, Mike Turquette wrote:
> Dynamic voltage and frequency scaling (dvfs) is a common power saving
> technique in many of today's modern processors. This patch introduces a
> common clk rate-change notifier handler which scales voltage
> appropriately whenever clk_set_rate is called on an affected clock.
>
> There are three prerequisites to using this feature:
>
> 1) the affected clocks must be using the common clk framework
> 2) voltage must be scaled using the regulator framework
> 3) clock frequency and regulator voltage values must be paired via the
> OPP library
>
> If a platform or device meets these requirements then using the notifier
> handler is straightforward. A struct device is used as the basis for
> performing initial look-ups for clocks via clk_get and regulators via
> regulator_get. This means that notifiers are subscribed on a per-device
> basis and multiple devices can have notifiers subscribed to the same
> clock. Put another way, the voltage chosen for a rail during a call to
> clk_set_rate is a function of the device, not the clock.
>
> Signed-off-by: Mike Turquette <mturquette@linaro.org>
[...]
> +struct dvfs_info *dvfs_clk_notifier_register(struct dvfs_info_init *dii)
> +{
> + struct dvfs_info *di;
> + int ret = 0;
> +
> + if (!dii)
> + return ERR_PTR(-EINVAL);
> +
> + di = kzalloc(sizeof(struct dvfs_info), GFP_KERNEL);
> + if (!di)
> + return ERR_PTR(-ENOMEM);
> +
> + di->dev = dii->dev;
> + di->clk = clk_get(di->dev, dii->con_id);
> + if (IS_ERR(di->clk)) {
> + ret = -ENOMEM;
> + goto err;
> + }
> +
> + di->reg = regulator_get(di->dev, dii->reg_id);
> + if (IS_ERR(di->reg)) {
> + ret = -ENOMEM;
> + goto err;
> + }
> +
> + di->tol = dii->tol;
> + di->nb.notifier_call = dvfs_clk_notifier_handler;
> +
> + ret = clk_notifier_register(di->clk, &di->nb);
> +
> + if (ret)
> + goto err;

Shouldn't regulator_put() and clk_put() be called in the error path?

> +
> + return di;
> +
> +err:
> + kfree(di);
> + return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(dvfs_clk_notifier_register);
> +
> +void dvfs_clk_notifier_unregister(struct dvfs_info *di)
> +{
> + clk_notifier_unregister(di->clk, &di->nb);
> + clk_put(di->clk);
> + regulator_put(di->reg);
> + kfree(di);
> +}
> +EXPORT_SYMBOL_GPL(dvfs_clk_notifier_unregister);

Regards,
Francesco