From dde8437d06560366d8988c92b5774039ec703864 Mon Sep 17 00:00:00 2001 From: Vincent Guittot Date: Tue, 23 Oct 2012 01:21:49 +0200 Subject: [PATCH 1/4] PM / OPP: RCU reclaim synchronize_rcu() blocks the caller of opp_enable/disbale for a complete grace period. This blocking duration prevents any intensive use of the functions. Replace synchronize_rcu() by call_rcu() which will call our function for freeing the old opp element. The duration of opp_enable() and opp_disable() will be no more dependant of the grace period. Signed-off-by: Vincent Guittot Reviewed-by: Paul E. McKenney Signed-off-by: Rafael J. Wysocki --- drivers/base/power/opp.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c index d9468642fc41..1211210b15b0 100644 --- a/drivers/base/power/opp.c +++ b/drivers/base/power/opp.c @@ -65,6 +65,7 @@ struct opp { unsigned long u_volt; struct device_opp *dev_opp; + struct rcu_head head; }; /** @@ -441,6 +442,17 @@ int opp_add(struct device *dev, unsigned long freq, unsigned long u_volt) return 0; } +/** + * opp_free_rcu() - helper to clear the struct opp when grace period has + * elapsed without blocking the the caller of opp_set_availability + */ +static void opp_free_rcu(struct rcu_head *head) +{ + struct opp *opp = container_of(head, struct opp, head); + + kfree(opp); +} + /** * opp_set_availability() - helper to set the availability of an opp * @dev: device for which we do this operation @@ -512,7 +524,7 @@ static int opp_set_availability(struct device *dev, unsigned long freq, list_replace_rcu(&opp->node, &new_opp->node); mutex_unlock(&dev_opp_list_lock); - synchronize_rcu(); + call_rcu(&opp->head, opp_free_rcu); /* Notify the change of the OPP availability */ if (availability_req) @@ -522,13 +534,10 @@ static int opp_set_availability(struct device *dev, unsigned long freq, srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_DISABLE, new_opp); - /* clean up old opp */ - new_opp = opp; - goto out; + return 0; unlock: mutex_unlock(&dev_opp_list_lock); -out: kfree(new_opp); return r; } From 80126ce7aeb4e187429681ef8a7785b7dcd7a348 Mon Sep 17 00:00:00 2001 From: Liam Girdwood Date: Tue, 23 Oct 2012 01:27:44 +0200 Subject: [PATCH 2/4] PM / OPP: Export symbols for module usage. Export the OPP functions for use by driver modules. Cc: "Rafael J. Wysocki" Cc: Kevin Hilman Cc: linux-pm@vger.kernel.org Cc: linux-kernel@vger.kernel.org [nm@ti.com: expansion of functions exported] Signed-off-by: Nishanth Menon Signed-off-by: Liam Girdwood Acked-by: Kevin Hilman Signed-off-by: Rafael J. Wysocki --- drivers/base/power/opp.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c index 1211210b15b0..66888861f9eb 100644 --- a/drivers/base/power/opp.c +++ b/drivers/base/power/opp.c @@ -23,6 +23,7 @@ #include #include #include +#include /* * Internal data structure organization with the OPP layer library is as @@ -161,6 +162,7 @@ unsigned long opp_get_voltage(struct opp *opp) return v; } +EXPORT_SYMBOL(opp_get_voltage); /** * opp_get_freq() - Gets the frequency corresponding to an available opp @@ -190,6 +192,7 @@ unsigned long opp_get_freq(struct opp *opp) return f; } +EXPORT_SYMBOL(opp_get_freq); /** * opp_get_opp_count() - Get number of opps available in the opp list @@ -222,6 +225,7 @@ int opp_get_opp_count(struct device *dev) return count; } +EXPORT_SYMBOL(opp_get_opp_count); /** * opp_find_freq_exact() - search for an exact frequency @@ -269,6 +273,7 @@ struct opp *opp_find_freq_exact(struct device *dev, unsigned long freq, return opp; } +EXPORT_SYMBOL(opp_find_freq_exact); /** * opp_find_freq_ceil() - Search for an rounded ceil freq @@ -311,6 +316,7 @@ struct opp *opp_find_freq_ceil(struct device *dev, unsigned long *freq) return opp; } +EXPORT_SYMBOL(opp_find_freq_ceil); /** * opp_find_freq_floor() - Search for a rounded floor freq @@ -357,6 +363,7 @@ struct opp *opp_find_freq_floor(struct device *dev, unsigned long *freq) return opp; } +EXPORT_SYMBOL(opp_find_freq_floor); /** * opp_add() - Add an OPP table from a table definitions @@ -561,6 +568,7 @@ int opp_enable(struct device *dev, unsigned long freq) { return opp_set_availability(dev, freq, true); } +EXPORT_SYMBOL(opp_enable); /** * opp_disable() - Disable a specific OPP @@ -582,6 +590,7 @@ int opp_disable(struct device *dev, unsigned long freq) { return opp_set_availability(dev, freq, false); } +EXPORT_SYMBOL(opp_disable); #ifdef CONFIG_CPU_FREQ /** From 0779726cc265805d0f7c7dd1d791fa4076b31a9a Mon Sep 17 00:00:00 2001 From: Nishanth Menon Date: Wed, 24 Oct 2012 22:00:12 +0200 Subject: [PATCH 3/4] PM / OPP: predictable fail results for opp_find* functions, v2 Currently the opp_find* functions return -ENODEV when: a) it cant find a device (e.g. request for an OPP search on device which was not registered) b) When it cant find a match for the search strategy used This makes life a little in-efficient for users such as devfreq to make reasonable judgement before switching search strategies. So, standardize the return results as following: -EINVAL for bad pointer parameters -ENODEV when device cannot be found -ERANGE when search fails This has the following benefit for devfreq implementation: The search fails when an unregistered device pointer is provided. This is a trigger to change the search direction and search for a better fit, however, if we cannot differentiate between a valid search range failure Vs an unregistered device, second search goes through the same fail return condition. This can be avoided by appropriate handling of error return code. With this change, we also fix devfreq for the improved search strategy with updated error code. Signed-off-by: Nishanth Menon Reviewed-by: Kevin Hilman Acked-by: MyungJoo Ham Signed-off-by: Rafael J. Wysocki --- drivers/base/power/opp.c | 27 +++++++++++++++++++-------- drivers/devfreq/devfreq.c | 4 ++-- 2 files changed, 21 insertions(+), 10 deletions(-) diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c index 66888861f9eb..c8a908b099c0 100644 --- a/drivers/base/power/opp.c +++ b/drivers/base/power/opp.c @@ -235,7 +235,10 @@ EXPORT_SYMBOL(opp_get_opp_count); * * Searches for exact match in the opp list and returns pointer to the matching * opp if found, else returns ERR_PTR in case of error and should be handled - * using IS_ERR. + * using IS_ERR. Error return values can be: + * EINVAL: for bad pointer + * ERANGE: no match found for search + * ENODEV: if device not found in list of registered devices * * Note: available is a modifier for the search. if available=true, then the * match is for exact matching frequency and is available in the stored OPP @@ -254,7 +257,7 @@ struct opp *opp_find_freq_exact(struct device *dev, unsigned long freq, bool available) { struct device_opp *dev_opp; - struct opp *temp_opp, *opp = ERR_PTR(-ENODEV); + struct opp *temp_opp, *opp = ERR_PTR(-ERANGE); dev_opp = find_device_opp(dev); if (IS_ERR(dev_opp)) { @@ -284,7 +287,11 @@ EXPORT_SYMBOL(opp_find_freq_exact); * for a device. * * Returns matching *opp and refreshes *freq accordingly, else returns - * ERR_PTR in case of error and should be handled using IS_ERR. + * ERR_PTR in case of error and should be handled using IS_ERR. Error return + * values can be: + * EINVAL: for bad pointer + * ERANGE: no match found for search + * ENODEV: if device not found in list of registered devices * * Locking: This function must be called under rcu_read_lock(). opp is a rcu * protected pointer. The reason for the same is that the opp pointer which is @@ -295,7 +302,7 @@ EXPORT_SYMBOL(opp_find_freq_exact); struct opp *opp_find_freq_ceil(struct device *dev, unsigned long *freq) { struct device_opp *dev_opp; - struct opp *temp_opp, *opp = ERR_PTR(-ENODEV); + struct opp *temp_opp, *opp = ERR_PTR(-ERANGE); if (!dev || !freq) { dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq); @@ -304,7 +311,7 @@ struct opp *opp_find_freq_ceil(struct device *dev, unsigned long *freq) dev_opp = find_device_opp(dev); if (IS_ERR(dev_opp)) - return opp; + return ERR_CAST(dev_opp); list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) { if (temp_opp->available && temp_opp->rate >= *freq) { @@ -327,7 +334,11 @@ EXPORT_SYMBOL(opp_find_freq_ceil); * for a device. * * Returns matching *opp and refreshes *freq accordingly, else returns - * ERR_PTR in case of error and should be handled using IS_ERR. + * ERR_PTR in case of error and should be handled using IS_ERR. Error return + * values can be: + * EINVAL: for bad pointer + * ERANGE: no match found for search + * ENODEV: if device not found in list of registered devices * * Locking: This function must be called under rcu_read_lock(). opp is a rcu * protected pointer. The reason for the same is that the opp pointer which is @@ -338,7 +349,7 @@ EXPORT_SYMBOL(opp_find_freq_ceil); struct opp *opp_find_freq_floor(struct device *dev, unsigned long *freq) { struct device_opp *dev_opp; - struct opp *temp_opp, *opp = ERR_PTR(-ENODEV); + struct opp *temp_opp, *opp = ERR_PTR(-ERANGE); if (!dev || !freq) { dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq); @@ -347,7 +358,7 @@ struct opp *opp_find_freq_floor(struct device *dev, unsigned long *freq) dev_opp = find_device_opp(dev); if (IS_ERR(dev_opp)) - return opp; + return ERR_CAST(dev_opp); list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) { if (temp_opp->available) { diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c index b146d76f04cf..4fa1a22c55ea 100644 --- a/drivers/devfreq/devfreq.c +++ b/drivers/devfreq/devfreq.c @@ -656,14 +656,14 @@ struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq, opp = opp_find_freq_floor(dev, freq); /* If not available, use the closest opp */ - if (opp == ERR_PTR(-ENODEV)) + if (opp == ERR_PTR(-ERANGE)) opp = opp_find_freq_ceil(dev, freq); } else { /* The freq is an lower bound. opp should be higher */ opp = opp_find_freq_ceil(dev, freq); /* If not available, use the closest opp */ - if (opp == ERR_PTR(-ENODEV)) + if (opp == ERR_PTR(-ERANGE)) opp = opp_find_freq_floor(dev, freq); } From ea83f81b489be3be268ed7fabfe8dd94bdc45a29 Mon Sep 17 00:00:00 2001 From: Wei Yongjun Date: Wed, 31 Oct 2012 01:29:17 +0100 Subject: [PATCH 4/4] PM / OPP: using kfree_rcu() to simplify the code The callback function of call_rcu() just calls a kfree(), so we can use kfree_rcu() instead of call_rcu() + callback function. dpatch engine is used to auto generate this patch. (https://github.com/weiyj/dpatch) Signed-off-by: Wei Yongjun Signed-off-by: Rafael J. Wysocki --- drivers/base/power/opp.c | 13 +------------ 1 file changed, 1 insertion(+), 12 deletions(-) diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c index c8a908b099c0..50b2831e027d 100644 --- a/drivers/base/power/opp.c +++ b/drivers/base/power/opp.c @@ -460,17 +460,6 @@ int opp_add(struct device *dev, unsigned long freq, unsigned long u_volt) return 0; } -/** - * opp_free_rcu() - helper to clear the struct opp when grace period has - * elapsed without blocking the the caller of opp_set_availability - */ -static void opp_free_rcu(struct rcu_head *head) -{ - struct opp *opp = container_of(head, struct opp, head); - - kfree(opp); -} - /** * opp_set_availability() - helper to set the availability of an opp * @dev: device for which we do this operation @@ -542,7 +531,7 @@ static int opp_set_availability(struct device *dev, unsigned long freq, list_replace_rcu(&opp->node, &new_opp->node); mutex_unlock(&dev_opp_list_lock); - call_rcu(&opp->head, opp_free_rcu); + kfree_rcu(opp, head); /* Notify the change of the OPP availability */ if (availability_req)