Re: [PATCH V5] PM/OPP: discard duplicate OPPs

From: Nishanth Menon
Date: Tue May 20 2014 - 11:19:28 EST


On 05/20/2014 09:53 AM, Viresh Kumar wrote:
> From: Chander Kashyap <k.chander@xxxxxxxxxxx>
>
> 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@xxxxxxxxxxx>
> Signed-off-by: Inderpal Singh <inderpal.s@xxxxxxxxxxx>
> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> ---
> V4->V5:
> - Mention Return values under 'Return:' clause of doc style comment.
> - s/pr_warn/dev_warn
> - s/linrao/linaro in my email id :(
>
> drivers/base/power/opp.c | 27 +++++++++++++++++++++++++--
> 1 file changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
> index 2553867..6a06d43 100644
> --- a/drivers/base/power/opp.c
> +++ b/drivers/base/power/opp.c
> @@ -394,6 +394,13 @@ EXPORT_SYMBOL_GPL(dev_pm_opp_find_freq_floor);
> * to keep the integrity of the internal data structures. Callers should ensure
> * that this function is *NOT* called under RCU protection or in contexts where
> * mutex cannot be locked.
> + *
> + * Returns:

s/Returns:/Return:/ -> sorry for being a nitpick.. scripts/kernel-doc
uses "Return:" in $section_return

> + * 0: On success OR
> + * Duplicate OPPs (both freq and volt are same) and opp->available
> + * -EEXIST: Freq are same and volt are different OR
> + * Duplicate OPPs (both freq and volt are same) and !opp->available
> + * -ENOMEM: Memory allocation failure
> */
> int dev_pm_opp_add(struct device *dev, unsigned long freq, unsigned long u_volt)
> {
> @@ -443,15 +450,31 @@ 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;
> +
> + dev_warn(dev, "%s: duplicate OPPs detected. Existing: freq: %lu, volt: %lu, enabled: %d. New: freq: %lu, volt: %lu, enabled: %d\n",
> + __func__, opp->rate, opp->u_volt, opp->available,
> + new_opp->rate, new_opp->u_volt, new_opp->available);

checkpatch --strict showed:
--- /tmp/kernel-patch-verify.22670/ptest_check-start 2014-05-20
10:07:15.736147182 -0500
+++ /tmp/kernel-patch-verify.22670/ptest_check-end 2014-05-20
10:07:15.960149013 -0500
@@ -0,0 +1,6 @@
+CHECK: Alignment should match open parenthesis
+#68: FILE: drivers/base/power/opp.c:471:
++ dev_warn(dev, "%s: duplicate OPPs detected. Existing:
freq: %lu, volt: %lu, enabled: %d. New: freq: %lu, volt: %lu, enabled:
%d\n",
++ __func__, opp->rate, opp->u_volt,
opp->available,

+If any of these errors are false positives, please report
+them to the maintainer, see CHECKPATCH in MAINTAINERS.


> + mutex_unlock(&dev_opp_list_lock);
> + kfree(new_opp);
> + return ret;
> + }
> +
> list_add_rcu(&new_opp->node, head);
> mutex_unlock(&dev_opp_list_lock);
>
>

Other than these minor fixes,
Acked-by: Nishanth Menon <nm@xxxxxx>

--
Regards,
Nishanth Menon
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