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Date: Tue, 20 May 2014 09:27:47 -0500 From: Nishanth Menon <nm@...com> To: Viresh Kumar <viresh.kumar@...aro.org>, <rjw@...ysocki.net> CC: <linaro-kernel@...ts.linaro.org>, <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <arvind.chauhan@....com>, <inderpal.s@...sung.com>, <chander.kashyap@...aro.org>, <pavel@....cz>, <len.brown@...el.com>, Chander Kashyap <k.chander@...sung.com>, Viresh Kumar <viresh.kumar@...rao.org> Subject: Re: [PATCH V4] PM/OPP: discard duplicate OPPs On 05/20/2014 09:17 AM, Viresh Kumar wrote: > From: Chander Kashyap <k.chander@...sung.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.chander@...sung.com> > Signed-off-by: Inderpal Singh <inderpal.s@...sung.com> > Signed-off-by: Viresh Kumar <viresh.kumar@...rao.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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