linux.git/drivers/base/power/opp/core.c, branch v4.14

PM / OPP: Call notifier without holding opp_table->lock

2017-09-25T22:44:32+00:00

The notifier callbacks may want to call some OPP helper routines which
may try to take the same opp_table->lock again and cause a deadlock. One
such usecase was reported by Chanwoo Choi, where calling
dev_pm_opp_disable() leads us to the devfreq's OPP notifier handler,
which further calls dev_pm_opp_find_freq_floor() and it deadlocks.

We don't really need the opp_table->lock to be held across the notifier
call though, all we want to make sure is that the 'opp' doesn't get
freed while being used from within the notifier chain. We can do it with
help of dev_pm_opp_get/put() as well. Let's do it.

Cc: 4.11+  # 4.11+
Fixes: 5b650b388844 "PM / OPP: Take kref from _find_opp_table()"
Reported-by: Chanwoo Choi 
Tested-by: Chanwoo Choi 
Reviewed-by: Stephen Boyd 
Reviewed-by: Chanwoo Choi 
Signed-off-by: Viresh Kumar 
Signed-off-by: Rafael J. Wysocki

PM / OPP: Add dev_pm_opp_{set|put}_clkname()

2017-06-23T23:41:55+00:00

In order to support OPP switching, OPP layer needs to get pointer to the
clock for the device. Simple cases work fine without using the routines
added by this patch (i.e.  by passing connection-id as NULL), but for a
device with multiple clocks available, the OPP core needs to know the
exact name of the clk to use.

Add a new set of APIs to get that done.

Tested-by: Rajendra Nayak 
Signed-off-by: Viresh Kumar 
Reviewed-by: Stephen Boyd 
Signed-off-by: Rafael J. Wysocki

PM / OPP: Don't create copy of regulators unnecessarily

2017-06-22T01:15:30+00:00

This code was required while the OPP core was managed with help of RCUs,
but not anymore. Get rid of unnecessary alloc/memcpy operations.

Signed-off-by: Viresh Kumar 
Reviewed-by: Stephen Boyd 
Signed-off-by: Rafael J. Wysocki

PM / OPP: Reorganize _generic_set_opp_regulator()

2017-06-22T01:15:29+00:00

The code was overly complicated here because of the limitations that we
had with RCUs (Couldn't use opp-table and OPPs outside RCU protected
section and can't call sleep-able routines from within that). But that
is long gone now.

Reorganize _generic_set_opp_regulator() in order to avoid using "struct
dev_pm_set_opp_data" and copying data into it for the case where
opp_table->set_opp is not set.

Signed-off-by: Viresh Kumar 
Reviewed-by: Stephen Boyd 
Signed-off-by: Rafael J. Wysocki

PM / OPP: fix off-by-one bug in dev_pm_opp_get_max_volt_latency loop

2017-02-23T22:00:31+00:00

Reading array at given index before checking if index is valid results in
illegal memory access.

The bug was detected using KASAN framework.

Signed-off-by: Andrzej Hajda 
Acked-by: Viresh Kumar 
Signed-off-by: Rafael J. Wysocki

PM / OPP: Make _find_opp_table_unlocked() static

2017-02-07T12:39:25+00:00

Fixes the following sparse warning:

drivers/base/power/opp/core.c:49:18: warning:
 symbol '_find_opp_table_unlocked' was not declared. Should it be static?

Signed-off-by: Wei Yongjun 
Reviewed-by: Stephen Boyd 
Acked-by: Viresh Kumar 
Signed-off-by: Rafael J. Wysocki

PM / OPP: Simplify dev_pm_opp_get_max_volt_latency()

2017-01-30T08:22:22+00:00

dev_pm_opp_get_max_volt_latency() calls _find_opp_table() two times
effectively.

Merge _get_regulator_count() into dev_pm_opp_get_max_volt_latency() to
avoid that.

Signed-off-by: Viresh Kumar 
Reviewed-by: Stephen Boyd 
Signed-off-by: Rafael J. Wysocki

PM / OPP: Simplify _opp_set_availability()

2017-01-30T08:22:22+00:00

As we don't use RCU locking anymore, there is no need to replace an
earlier OPP node with a new one. Just update the existing one.

Signed-off-by: Viresh Kumar 
Reviewed-by: Stephen Boyd 
Signed-off-by: Rafael J. Wysocki

PM / OPP: Move away from RCU locking

2017-01-30T08:22:22+00:00

The RCU locking isn't well suited for the OPP core. The RCU locking fits
better for reader heavy stuff, while the OPP core have at max one or two
readers only at a time.

Over that, it was getting very confusing the way RCU locking was used
with the OPP core. The individual OPPs are mostly well handled, i.e. for
an update a new structure was created and then that replaced the older
one. But the OPP tables were updated directly all the time from various
parts of the core. Though they were mostly used from within RCU locked
region, they didn't had much to do with RCU and were governed by the
mutex instead.

And that mixed with the 'opp_table_lock' has made the core even more
confusing.

Now that we are already managing the OPPs and the OPP tables with kernel
reference infrastructure, we can get rid of RCU locking completely and
simplify the code a lot.

Remove all RCU references from code and comments.

Acquire opp_table->lock while parsing the list of OPPs though.

Signed-off-by: Viresh Kumar 
Reviewed-by: Stephen Boyd 
Signed-off-by: Rafael J. Wysocki

PM / OPP: Take kref from _find_opp_table()

2017-01-30T08:22:22+00:00

Take reference of the OPP table from within _find_opp_table(). Also
update the callers of _find_opp_table() to call
dev_pm_opp_put_opp_table() after they have used the OPP table.

Note that _find_opp_table() increments the reference under the
opp_table_lock.

Now that the OPP table wouldn't get freed until the callers of
_find_opp_table() call dev_pm_opp_put_opp_table(), there is no need to
take the opp_table_lock or rcu_read_lock() around it. Drop them.

Signed-off-by: Viresh Kumar 
Reviewed-by: Stephen Boyd 
Signed-off-by: Rafael J. Wysocki