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  1. 04 Apr, 2013 24 commits
  3. 03 Apr, 2013 7 commits
  5. 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
  7. 27 Mar, 2013 6 commits
  9. 26 Mar, 2013 1 commit
    • Prashant Gaikwad's avatar
      clk: Add composite clock type · ece70094
      Prashant Gaikwad authored 
      Not all clocks are required to be decomposed into basic clock
types but at the same time want to use the functionality
provided by these basic clock types instead of duplicating.

For example, Tegra SoC has ~100 clocks which can be decomposed
into Mux -> Div -> Gate clock types making the clock count to
~300. Also, parent change operation can not be performed on gate
clock which forces to use mux clock in driver if want to change
the parent.

Instead aggregate the basic clock types functionality into one
clock and just use this clock for all operations. This clock
type re-uses the functionality of basic clock types and not
limited to basic clock types but any hardware-specific
implementation.
Signed-off-by: default avatarPrashant Gaikwad <pgaikwad@nvidia.com>
Signed-off-by: default avatarMike Turquette <mturquette@linaro.org>
      ece70094
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