cpufreq: Add per policy governor-init/exit infrastructure

Currently, there can't be multiple instances of single governor_type.
If we have a multi-package system, where we have multiple instances
of struct policy (per package), we can't have multiple instances of
same governor. i.e. We can't have multiple instances of ondemand
governor for multiple packages.

Governors directory in sysfs is created at /sys/devices/system/cpu/cpufreq/
governor-name/. Which again reflects that there can be only one
instance of a governor_type in the system.

This is a bottleneck for multicluster system, where we want different
packages to use same governor type, but with different tunables.

This patch is inclined towards providing this infrastructure. Because
we are required to allocate governor's resources dynamically now, we
must do it at policy creation and end. And so got
CPUFREQ_GOV_POLICY_INIT/EXIT.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
cpufreq: Don't call __cpufreq_governor() for drivers without target()

Some cpufreq drivers implement their own governor and so don't need
us to call generic governors interface via __cpufreq_governor(). Few
recent commits haven't obeyed this law well and we saw some
regressions.

This patch is an attempt to fix the above issue.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reported-and-tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Tested-by: Dirk Brandewie <dirk.brandewie@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
cpufreq: Issue CPUFREQ_GOV_POLICY_EXIT notifier before dropping policy refcount

We must call __cpufreq_governor(data, CPUFREQ_GOV_POLICY_EXIT) before
calling cpufreq_cpu_put(data), so that policy kobject have valid
fields. Otherwise, removing last online cpu of policy->cpus causes
this crash for ondemand/conservative governor.

 [<c00fb076>] (sysfs_find_dirent+0xe/0xa8) from [<c00fb1bd>] (sysfs_get_dirent+0x21/0x58)
 [<c00fb1bd>] (sysfs_get_dirent+0x21/0x58) from [<c00fc259>] (sysfs_remove_group+0x85/0xbc)
 [<c00fc259>] (sysfs_remove_group+0x85/0xbc) from [<c02faad9>] (cpufreq_governor_dbs+0x369/0x4a0)
 [<c02faad9>] (cpufreq_governor_dbs+0x369/0x4a0) from [<c02f66d7>] (__cpufreq_governor+0x2b/0x8c)
 [<c02f66d7>] (__cpufreq_governor+0x2b/0x8c) from [<c02f6893>] (__cpufreq_remove_dev.isra.12+0x15b/0x250)
 [<c02f6893>] (__cpufreq_remove_dev.isra.12+0x15b/0x250) from [<c03e91c7>] (cpufreq_cpu_callback+0x2f/0x3c)
 [<c03e91c7>] (cpufreq_cpu_callback+0x2f/0x3c) from [<c0036fe1>] (notifier_call_chain+0x45/0x54)
 [<c0036fe1>] (notifier_call_chain+0x45/0x54) from [<c001e611>] (__cpu_notify+0x1d/0x34)
 [<c001e611>] (__cpu_notify+0x1d/0x34) from [<c03e5833>] (_cpu_down+0x63/0x1ac)
 [<c03e5833>] (_cpu_down+0x63/0x1ac) from [<c03e5997>] (cpu_down+0x1b/0x30)
 [<c03e5997>] (cpu_down+0x1b/0x30) from [<c03e60eb>] (store_online+0x27/0x54)
 [<c03e60eb>] (store_online+0x27/0x54) from [<c0295629>] (dev_attr_store+0x11/0x18)
 [<c0295629>] (dev_attr_store+0x11/0x18) from [<c00f9edd>] (sysfs_write_file+0xed/0x114)
 [<c00f9edd>] (sysfs_write_file+0xed/0x114) from [<c00b42a9>] (vfs_write+0x65/0xd8)
 [<c00b42a9>] (vfs_write+0x65/0xd8) from [<c00b4523>] (sys_write+0x2f/0x50)
 [<c00b4523>] (sys_write+0x2f/0x50) from [<c000cdc1>] (ret_fast_syscall+0x1/0x52)

Of course this only impacted drivers which have
have_governor_per_policy set to true. i.e. big LITTLE cpufreq driver.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
cpufreq: Drop rwsem lock around CPUFREQ_GOV_POLICY_EXIT

With the rwsem lock around
__cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT), we
get circular dependency when we call sysfs_remove_group().

 ======================================================
 [ INFO: possible circular locking dependency detected ]
 3.9.0-rc7+ #15 Not tainted
 -------------------------------------------------------
 cat/2387 is trying to acquire lock:
  (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [<c02f6179>] lock_policy_rwsem_read+0x25/0x34

 but task is already holding lock:
  (s_active#41){++++.+}, at: [<c00f9bf7>] sysfs_read_file+0x4f/0xcc

 which lock already depends on the new lock.

 the existing dependency chain (in reverse order) is:

-> #1 (s_active#41){++++.+}:
        [<c0055a79>] lock_acquire+0x61/0xbc
        [<c00fabf1>] sysfs_addrm_finish+0xc1/0x128
        [<c00f9819>] sysfs_hash_and_remove+0x35/0x64
        [<c00fbe6f>] remove_files.isra.0+0x1b/0x24
        [<c00fbea5>] sysfs_remove_group+0x2d/0xa8
        [<c02f9a0b>] cpufreq_governor_interactive+0x13b/0x35c
        [<c02f61df>] __cpufreq_governor+0x2b/0x8c
        [<c02f6579>] __cpufreq_set_policy+0xa9/0xf8
        [<c02f6b75>] store_scaling_governor+0x61/0x100
        [<c02f6f4d>] store+0x39/0x60
        [<c00f9b81>] sysfs_write_file+0xed/0x114
        [<c00b3fd1>] vfs_write+0x65/0xd8
        [<c00b424b>] sys_write+0x2f/0x50
        [<c000cdc1>] ret_fast_syscall+0x1/0x52

-> #0 (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}:
        [<c0055253>] __lock_acquire+0xef3/0x13dc
        [<c0055a79>] lock_acquire+0x61/0xbc
        [<c03ee1f5>] down_read+0x25/0x30
        [<c02f6179>] lock_policy_rwsem_read+0x25/0x34
        [<c02f6edd>] show+0x21/0x58
        [<c00f9c0f>] sysfs_read_file+0x67/0xcc
        [<c00b40a7>] vfs_read+0x63/0xd8
        [<c00b41fb>] sys_read+0x2f/0x50
        [<c000cdc1>] ret_fast_syscall+0x1/0x52

 other info that might help us debug this:

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(s_active#41);
                                lock(&per_cpu(cpu_policy_rwsem, cpu));
                                lock(s_active#41);
   lock(&per_cpu(cpu_policy_rwsem, cpu));

  *** DEADLOCK ***

 2 locks held by cat/2387:
  #0:  (&buffer->mutex){+.+.+.}, at: [<c00f9bcd>] sysfs_read_file+0x25/0xcc
  #1:  (s_active#41){++++.+}, at: [<c00f9bf7>] sysfs_read_file+0x4f/0xcc

 stack backtrace:
 [<c0011d55>] (unwind_backtrace+0x1/0x9c) from [<c03e9a09>] (print_circular_bug+0x19d/0x1e8)
 [<c03e9a09>] (print_circular_bug+0x19d/0x1e8) from [<c0055253>] (__lock_acquire+0xef3/0x13dc)
 [<c0055253>] (__lock_acquire+0xef3/0x13dc) from [<c0055a79>] (lock_acquire+0x61/0xbc)
 [<c0055a79>] (lock_acquire+0x61/0xbc) from [<c03ee1f5>] (down_read+0x25/0x30)
 [<c03ee1f5>] (down_read+0x25/0x30) from [<c02f6179>] (lock_policy_rwsem_read+0x25/0x34)
 [<c02f6179>] (lock_policy_rwsem_read+0x25/0x34) from [<c02f6edd>] (show+0x21/0x58)
 [<c02f6edd>] (show+0x21/0x58) from [<c00f9c0f>] (sysfs_read_file+0x67/0xcc)
 [<c00f9c0f>] (sysfs_read_file+0x67/0xcc) from [<c00b40a7>] (vfs_read+0x63/0xd8)
 [<c00b40a7>] (vfs_read+0x63/0xd8) from [<c00b41fb>] (sys_read+0x2f/0x50)
 [<c00b41fb>] (sys_read+0x2f/0x50) from [<c000cdc1>] (ret_fast_syscall+0x1/0x52)

This lock isn't required while calling __cpufreq_governor(policy,
CPUFREQ_GOV_POLICY_EXIT). Remove it.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>