On Tue, May 13, 2014 at 2:41 AM, [Chander Kashyap
<chander.kash...@linaro.org> wrote:
> From: Chander Kashyap <k.chan...@samsung.com>
>
> It may be possible to unregister and re-register the cpufreq driver.
> One such example is arm big-little IKS cpufreq driver. While
> re-registering the driver, same OPPs may get added again.
>
> This patch detects the duplicacy and discards them.
Nice catch. Thanks for the same.
That said, instead of ignoring it (skipping addition), should we do
the following:
a) if we find the same OPP being added, return error
b) add a cleanup routine dev_pm_opp_remove ?
Original design required OPP entries added by platform code and used
by driver code, but things have changed over time.
>
> Signed-off-by: Chander Kashyap <k.chan...@samsung.com>
> Signed-off-by: Inderpal Singh <inderpa...@samsung.com>
> ---
> drivers/base/power/opp.c | 28 +++++++++++++++++++---------
> 1 file changed, 19 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
> index 2553867..2e803a9 100644
> --- a/drivers/base/power/opp.c
> +++ b/drivers/base/power/opp.c
> @@ -443,23 +443,33 @@ int dev_pm_opp_add(struct device *dev, unsigned long
> freq, unsigned long u_volt)
> new_opp->u_volt = u_volt;
> new_opp->available = true;
>
> - /* Insert new OPP in order of increasing frequency */
> + /*
> + * Insert new OPP in order of increasing frequency
> + * and discard if already present
> + */
> head = &dev_opp->opp_list;
> list_for_each_entry_rcu(opp, &dev_opp->opp_list, node) {
> - if (new_opp->rate < opp->rate)
> + if (new_opp->rate <= opp->rate)
> break;
> else
> head = &opp->node;
> }
>
say we do at this point:
if (new_opp->rate == opp->rate) {
dev_err(dev, "%s: attempt to add duplicate OPP entry (rate=%ld)\n",
__func__, new_opp->rate)
kfree(new_opp);
return -EINVAL;
}
we could avoid the change below, right?
> - list_add_rcu(&new_opp->node, head);
> - mutex_unlock(&dev_opp_list_lock);
> + if (new_opp->rate != opp->rate) {
> + list_add_rcu(&new_opp->node, head);
> + mutex_unlock(&dev_opp_list_lock);
> +
> + /*
> + * Notify the changes in the availability of the operable
> + * frequency/voltage list.
> + */
> + srcu_notifier_call_chain(&dev_opp->head,
> + OPP_EVENT_ADD, new_opp);
> + } else {
> + mutex_unlock(&dev_opp_list_lock);
> + kfree(new_opp);
> + }
>
> - /*
> - * Notify the changes in the availability of the operable
> - * frequency/voltage list.
> - */
> - srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_ADD, new_opp);
> return 0;
> }
> EXPORT_SYMBOL_GPL(dev_pm_opp_add);
> --
> 1.7.9.5
>
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