cpufreq: OMAP: use RCU locks around usage of OPP

OPP pointer is RCU protected, hence after finding it, de-reference
also should be protected with the same RCU context else the OPP
pointer may become invalid.

Reported-by: Alexander Holler <holler@ahsoftware.de>
Tested-by: Alexander Holler <holler@ahsoftware.de>
Acked-by: Alexander Holler <holler@ahsoftware.de>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
cpufreq: cpufreq-cpu0: use RCU locks around usage of OPP

OPP pointer is RCU protected, hence after finding it, de-reference
also should be protected with the same RCU context else the OPP
pointer may become invalid.

Reported-by: Jack Mitchell <jack@embed.me.uk>
Tested-by: Alexander Holler <holler@ahsoftware.de>
Tested-by: Jack Mitchell <jack@embed.me.uk>
Acked-by: Alexander Holler <holler@ahsoftware.de>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM / devfreq: add locking documentation for recommended_opp

OPP pointers are protected by RCU locks, the pointer validity is
permissible only under the section of rcu_read_lock to rcu_read_unlock

Add documentation to the effect.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM / devfreq: exynos4_bus: honor RCU lock usage

OPP pointers cannot be expected to be valid beyond the boundary
of rcu_read_lock and rcu_read_unlock. Unfortunately, the current
exynos4 busfreq driver does not honor the usage constraint and stores
the OPP pointer in struct busfreq_data. This could potentially
become invalid later such as: across devfreq opp change decisions,
resulting in unpredictable behavior.

To fix this, we introduce a busfreq specific busfreq_opp_info
structure which is used to handle OPP information. OPP information
is de-referenced to voltage and frequency pairs as needed into
busfreq_opp_info structure and used as needed.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
ACPI: Check MSR valid bit before using P-state frequencies

To fix incorrect P-state frequencies which can happen on
some AMD systems f594065faf4f9067c2283a34619fc0714e79a98d
   "ACPI: Add fixups for AMD P-state figures"
introduced a quirk to obtain the correct values by reading
from AMD specific MSRs.

This did cause a regression when running a kernel using that
quirk under Xen which does (currently) not pass through MSR
reads to the HW. Instead the guest gets a 0 in return.
And this seems to cause a failure to initialize the ondemand
governour (hard to say for sure as all P-states appear to run
at the same frequency).

While this should also be fixed in the hypervisor (to allow
a guest to read that MSR), this patch is intended to work
around the issue in the meantime. In discussion it turned out
that indeed real HW/BIOSes may choose to not set the valid bit
and thus mark the P-state as invalid. So this could be considered
a fix for broken BIOSes that also works around the issue on Xen.

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Cc: 3.7+ <stable@vger.kernel.org>
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
cpufreq: Add module aliases for acpi-cpufreq

The acpi core will call request_module("acpi-cpufreq") on subsystem init,
but this will fail if the module isn't available at that stage of boot.
Add some module aliases to ensure that udev can load the module on Intel
and AMD systems with the appropriate feature bits - I /think/ that this
will also work on VIA systems, but haven't verified that.

References: http://lkml.kernel.org/r/1448223.sdUJnNSRz4@vostro.rjw.lan
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Tested-by: Leonid Isaev <lisaev@umail.iu.edu>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: 3.7+ <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>