Fix below build warning:

  CC      arch/arm/mach-omap2/hwspinlock.o
In file included from arch/arm/mach-omap2/hwspinlock.c:22:
include/linux/hwspinlock.h: In function '__hwspin_unlock':
include/linux/hwspinlock.h:121: warning: 'return' with a value, in function returning void
Signed-off-by: NAxel Lin <axel.lin@gmail.com>
Signed-off-by: NOhad Ben-Cohen <ohad@wizery.com>

Hardware Spinlock devices usually contain numerous locks (known
devices today support between 32 to 256 locks).

Originally hwspinlock core required drivers to register (and later,
when needed, unregister) each lock separately.

That worked, but required hwspinlocks drivers to do a bit extra work
when they were probed/removed.

This patch changes hwspin_lock_{un}register() to allow a bank of
hwspinlocks to be {un}registered in a single invocation.

A new 'struct hwspinlock_device', which contains an array of 'struct
hwspinlock's is now being passed to the core upon registration (so
instead of wrapping each struct hwspinlock, a priv member has been added
to allow drivers to piggyback their private data with each hwspinlock).

While at it, several per-lock members were moved to be per-device:
1. struct device *dev
2. struct hwspinlock_ops *ops

In addition, now that the array of locks is handled by the core,
there's no reason to maintain a per-lock 'int id' member: the id of the
lock anyway equals to its index in the bank's array plus the bank's
base_id.
Remove this per-lock id member too, and instead use a simple pointers
arithmetic to derive it.

As a result of this change, hwspinlocks drivers are now simpler and smaller
(about %20 code reduction) and the memory footprint of the hwspinlock
framework is reduced.
Signed-off-by: NOhad Ben-Cohen <ohad@wizery.com>

hwspinlock drivers must anyway select CONFIG_HWSPINLOCK,
so there's no point in having register/unregister stubs.

Removing those stubs will only make it easier for developers
to catch CONFIG_HWSPINLOCK mis-.config-urations.
Signed-off-by: NOhad Ben-Cohen <ohad@wizery.com>

hwspinlock devices provide system-wide hardware locks that are used
by remote processors that have no other way to achieve synchronization.

To achieve that, each physical lock must have a system-wide id number
that is agreed upon, otherwise remote processors can't possibly assume
they're using the same hardware lock.

Usually boards have a single hwspinlock device, which provides several
hwspinlocks, and in this case, they can be trivially numbered 0 to
(num-of-locks - 1).

In case boards have several hwspinlocks devices, a different base id
should be used for each hwspinlock device (they can't all use 0 as
a starting id!).

While this is certainly not common, it's just plain wrong to just
silently use 0 as a base id whenever the hwspinlock driver is probed.

This patch provides a hwspinlock_pdata structure, that boards can use
to set a different base id for each of the hwspinlock devices they may
have, and demonstrates how to use it with the omap hwspinlock driver.

While we're at it, make sure the hwspinlock core prints an explicit
error message in case an hwspinlock is registered with an id number
that already exists; this will help users catch such base id issues.
Reported-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NOhad Ben-Cohen <ohad@wizery.com>
Acked-by: NTony Lindgren <tony@atomide.com>

Add a platform-independent hwspinlock framework.

Hardware spinlock devices are needed, e.g., in order to access data
that is shared between remote processors, that otherwise have no
alternative mechanism to accomplish synchronization and mutual exclusion
operations.
Signed-off-by: NOhad Ben-Cohen <ohad@wizery.com>
Cc: Hari Kanigeri <h-kanigeri2@ti.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Russell King <linux@arm.linux.org.uk>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NTony Lindgren <tony@atomide.com>