Re: [PATCH V4] PM/OPP: discard duplicate OPPs

On 05/20/2014 09:17 AM, Viresh Kumar wrote:

From: Chander Kashyap k.chander@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.chander@samsung.com Signed-off-by: Inderpal Singh inderpal.s@samsung.com Signed-off-by: Viresh Kumar viresh.kumar@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.