Change the per-hwmod mutex to a spinlock. (The per-hwmod lock
serializes most post-initialization hwmod operations such as enable,
idle, and shutdown.) Spinlocks are needed, because in some cases,
hwmods must be enabled from timer interrupt disabled-context, such as
an ISR. The current use-case that is driving this is the OMAP GPIO
block ISR: it can trigger interrupts even with its clocks disabled,
but these clocks are needed for register accesses in the ISR to succeed.
This patch also effectively reverts commit
848240223c - this patch makes
_omap_hwmod_enable() and _omap_hwmod_init() static, renames them back
to _enable() and _idle(), and changes their callers to call the
spinlocking versions. Previously, since omap_hwmod_{enable,init}()
attempted to take mutexes, these functions could not be called while
the timer interrupt was disabled; but now that the functions use
spinlocks and save and restore the IRQ state, it is appropriate to
call them directly.
Kevin Hilman <khilman@deeprootsystems.com> originally proposed this
patch - thanks Kevin.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>
Cc: Benoît Cousson <b-cousson@ti.com>
dc6d1cda04