OMAP2+: hwmod: upgrade per-hwmod mutex to a spinlock

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
848240223c35fcc71c424ad51a8e8aef42d3879c - 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>

1 files changed, 3 insertions, 3 deletions

diff --git a/arch/arm/plat-omap/include/plat/omap_hwmod.h b/arch/arm/plat-omap/include/plat/omap_hwmod.h
index e4c4fd4cc1ed..b588f4779806 100644
--- a/arch/arm/plat-omap/include/plat/omap_hwmod.h
+++ b/arch/arm/plat-omap/include/plat/omap_hwmod.h
@@ -32,7 +32,7 @@
 #include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/ioport.h>
-#include <linux/mutex.h>
+#include <linux/spinlock.h>
 #include <plat/cpu.h>
 
 struct omap_device;
@@ -472,7 +472,7 @@ struct omap_hwmod_class {
  * @_postsetup_state: internal-use state to leave the hwmod in after _setup()
  * @flags: hwmod flags (documented below)
  * @omap_chip: OMAP chips this hwmod is present on
- * @_mutex: mutex serializing operations on this hwmod
+ * @_lock: spinlock serializing operations on this hwmod
  * @node: list node for hwmod list (internal use)
  *
  * @main_clk refers to this module's "main clock," which for our
@@ -502,7 +502,7 @@ struct omap_hwmod {
 	void				*dev_attr;
 	u32				_sysc_cache;
 	void __iomem			*_mpu_rt_va;
-	struct mutex			_mutex;
+	spinlock_t			_lock;
 	struct list_head		node;
 	u16				flags;
 	u8				_mpu_port_index;