On 05/20/2014 09:17 AM, Viresh Kumar wrote:
> From: Chander Kashyap <k.chan...@samsung.com>
>
> We don't have any protection against addition of duplicate OPPs currently and
> in case some code tries to add them it will end up corrupting OPP tables.
>
> There can be many combinations in which we may end up trying duplicate OPPs:
> - both freq and volt are same, but earlier OPP may or may not be active.
> - only freq is same and volt is different.
>
> This patch tries to implement below logic for these cases:
>
> Return 0 if new OPP was duplicate of existing one (i.e. same freq and volt)
> and
> return -EEXIST if new OPP had same freq but different volt as of an existing
> OPP
> OR if both freq/volt were same but earlier OPP was disabled.
>
> Signed-off-by: Chander Kashyap <k.chan...@samsung.com>
> Signed-off-by: Inderpal Singh <inderpa...@samsung.com>
> Signed-off-by: Viresh Kumar <viresh.ku...@linrao.org>
> ---
> V3->V4:
> - handle duplicate OPPs more appropriately
> - update comment over routine and enhance commit log
>
> @Chander: I have kept your authorship as is, hope you don't mind me sending it
> on your behalf :)
>
> drivers/base/power/opp.c | 25 +++++++++++++++++++++++--
> 1 file changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
> index 2553867..cd9af42 100644
> --- a/drivers/base/power/opp.c
> +++ b/drivers/base/power/opp.c
> @@ -389,6 +389,11 @@ EXPORT_SYMBOL_GPL(dev_pm_opp_find_freq_floor);
> * The opp is made available by default and it can be controlled using
> * dev_pm_opp_enable/disable functions.
> *
> + * Duplicate OPPs are discarded. Will return 0 if new OPP was duplicate of
> + * existing one (i.e. same freq and volt) and -EEXIST would be returned if
> new
> + * OPP had same freq but different volt as of an existing OPP OR if both were
> + * same but earlier OPP was disabled.
How about we use the kernel-doc's "Return:"
Return: Returns 0 if new OPP was successfully added OR if the new OPP
was exact duplicate of existing one (i.e. same frequency and volt).
-EEXIST would be returned if new
OPP had same freq but different volt as of an existing OPP OR if both
were same but earlier OPP was disabled. -ENOMEM is returned if there
is no memory available to allocate requisite internal structures.
> + *
> * 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
> @@ -443,15 +448,31 @@ 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;
> }
>
> + /* Duplicate OPPs ? */
> + if (new_opp->rate == opp->rate) {
> + int ret = (new_opp->u_volt == opp->u_volt) && opp->available ?
> + 0 : -EEXIST;
> +
> + pr_warn("%s: duplicate OPPs detected. Existing: freq: %lu,
> volt: %lu, enabled: %d. New: freq: %lu, volt: %lu, enabled: %d\n",
dev_warn please? we already know the dev pointer. Also can we reduce
this down to 80 character limit if possible?
> + __func__, opp->rate, opp->u_volt, opp->available,
> + new_opp->rate, new_opp->u_volt, new_opp->available);
> + mutex_unlock(&dev_opp_list_lock);
> + kfree(new_opp);
> + return ret;
> + }
> +
> list_add_rcu(&new_opp->node, head);
> mutex_unlock(&dev_opp_list_lock);
>
>
Otherwise, this looks fine to me.
--
Regards,
Nishanth Menon
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