1. 04 Apr, 2013 31 commits
  2. 03 Apr, 2013 7 commits
  3. 02 Apr, 2013 2 commits
    • Mike Turquette's avatar
      clk: allow reentrant calls into the clk framework · 533ddeb1
      Mike Turquette authored
      Reentrancy into the clock framework is necessary for clock operations
      that result in nested calls to the clk api.  A common example is a clock
      that is prepared via an i2c transaction, such as a clock inside of a
      discrete audio chip or a power management IC.  The i2c subsystem itself
      will use the clk api resulting in a deadlock:
      
      clk_prepare(audio_clk)
      	i2c_transfer(..)
      		clk_prepare(i2c_controller_clk)
      
      The ability to reenter the clock framework prevents this deadlock.
      
      Other use cases exist such as allowing .set_rate callbacks to call
      clk_set_parent to achieve the best rate, or to save power in certain
      configurations.  Yet another example is performing pinctrl operations
      from a clk_ops callback.  Calls into the pinctrl subsystem may call
      clk_{un}prepare on an unrelated clock.  Allowing for nested calls to
      reenter the clock framework enables both of these use cases.
      
      Reentrancy is implemented by two global pointers that track the owner
      currently holding a global lock.  One pointer tracks the owner during
      sleepable, mutex-protected operations and the other one tracks the owner
      during non-interruptible, spinlock-protected operations.
      
      When the clk framework is entered we try to hold the global lock.  If it
      is held we compare the current task against the current owner; a match
      implies a nested call and we reenter.  If the values do not match then
      we block on the lock until it is released.
      Signed-off-by: default avatarMike Turquette <mturquette@linaro.org>
      Cc: Rajagopal Venkat <rajagopal.venkat@linaro.org>
      Cc: David Brown <davidb@codeaurora.org>
      Tested-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
      Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
      533ddeb1
    • Mike Turquette's avatar
      clk: abstract locking out into helper functions · eab89f69
      Mike Turquette authored
      Create locking helpers for the global mutex and global spinlock.  The
      definitions of these helpers will be expanded upon in the next patch
      which introduces reentrancy into the locking scheme.
      Signed-off-by: default avatarMike Turquette <mturquette@linaro.org>
      Cc: Rajagopal Venkat <rajagopal.venkat@linaro.org>
      Cc: David Brown <davidb@codeaurora.org>
      Tested-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
      Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
      eab89f69