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:
- the affected clocks must be using the common clk framework
- voltage must be scaled using the regulator framework
- 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