• Ohad Ben-Cohen's avatar
    hwspinlock/core/omap: fix id issues on multiple hwspinlock devices · c3c1250e
    Ohad Ben-Cohen authored
    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: 's avatarArnd Bergmann <arnd@arndb.de>
    Signed-off-by: 's avatarOhad Ben-Cohen <ohad@wizery.com>
    Acked-by: 's avatarTony Lindgren <tony@atomide.com>
    c3c1250e
hwspinlock.h 10.9 KB