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OMAP2+: hwmod: upgrade per-hwmod mutex to a spinlock
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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
8482402 - 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>
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Paul Walmsley committed Dec 22, 2010
1 parent bd36179 commit dc6d1cd
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Showing 3 changed files with 64 additions and 56 deletions.
105 changes: 59 additions & 46 deletions arch/arm/mach-omap2/omap_hwmod.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -135,6 +135,7 @@
#include <linux/err.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>

#include <plat/common.h>
#include <plat/cpu.h>
Expand Down Expand Up @@ -1192,17 +1193,14 @@ static int _reset(struct omap_hwmod *oh)
}

/**
* _omap_hwmod_enable - enable an omap_hwmod
* _enable - enable an omap_hwmod
* @oh: struct omap_hwmod *
*
* Enables an omap_hwmod @oh such that the MPU can access the hwmod's
* register target. (This function has a full name --
* _omap_hwmod_enable() rather than simply _enable() -- because it is
* currently required by the pm34xx.c idle loop.) Returns -EINVAL if
* the hwmod is in the wrong state or passes along the return value of
* _wait_target_ready().
* register target. Returns -EINVAL if the hwmod is in the wrong
* state or passes along the return value of _wait_target_ready().
*/
int _omap_hwmod_enable(struct omap_hwmod *oh)
static int _enable(struct omap_hwmod *oh)
{
int r;

Expand Down Expand Up @@ -1249,16 +1247,14 @@ int _omap_hwmod_enable(struct omap_hwmod *oh)
}

/**
* _omap_hwmod_idle - idle an omap_hwmod
* _idle - idle an omap_hwmod
* @oh: struct omap_hwmod *
*
* Idles an omap_hwmod @oh. This should be called once the hwmod has
* no further work. (This function has a full name --
* _omap_hwmod_idle() rather than simply _idle() -- because it is
* currently required by the pm34xx.c idle loop.) Returns -EINVAL if
* the hwmod is in the wrong state or returns 0.
* no further work. Returns -EINVAL if the hwmod is in the wrong
* state or returns 0.
*/
int _omap_hwmod_idle(struct omap_hwmod *oh)
static int _idle(struct omap_hwmod *oh)
{
if (oh->_state != _HWMOD_STATE_ENABLED) {
WARN(1, "omap_hwmod: %s: idle state can only be entered from "
Expand Down Expand Up @@ -1304,11 +1300,11 @@ static int _shutdown(struct omap_hwmod *oh)
if (oh->class->pre_shutdown) {
prev_state = oh->_state;
if (oh->_state == _HWMOD_STATE_IDLE)
_omap_hwmod_enable(oh);
_enable(oh);
ret = oh->class->pre_shutdown(oh);
if (ret) {
if (prev_state == _HWMOD_STATE_IDLE)
_omap_hwmod_idle(oh);
_idle(oh);
return ret;
}
}
Expand Down Expand Up @@ -1381,7 +1377,7 @@ static int _setup(struct omap_hwmod *oh, void *data)
if ((oh->flags & HWMOD_INIT_NO_RESET) && oh->rst_lines_cnt == 1)
return 0;

r = _omap_hwmod_enable(oh);
r = _enable(oh);
if (r) {
pr_warning("omap_hwmod: %s: cannot be enabled (%d)\n",
oh->name, oh->_state);
Expand All @@ -1393,7 +1389,7 @@ static int _setup(struct omap_hwmod *oh, void *data)

/*
* OCP_SYSCONFIG bits need to be reprogrammed after a softreset.
* The _omap_hwmod_enable() function should be split to
* The _enable() function should be split to
* avoid the rewrite of the OCP_SYSCONFIG register.
*/
if (oh->class->sysc) {
Expand All @@ -1415,7 +1411,7 @@ static int _setup(struct omap_hwmod *oh, void *data)
postsetup_state = _HWMOD_STATE_ENABLED;

if (postsetup_state == _HWMOD_STATE_IDLE)
_omap_hwmod_idle(oh);
_idle(oh);
else if (postsetup_state == _HWMOD_STATE_DISABLED)
_shutdown(oh);
else if (postsetup_state != _HWMOD_STATE_ENABLED)
Expand Down Expand Up @@ -1521,7 +1517,7 @@ int omap_hwmod_register(struct omap_hwmod *oh)

list_add_tail(&oh->node, &omap_hwmod_list);

mutex_init(&oh->_mutex);
spin_lock_init(&oh->_lock);

oh->_state = _HWMOD_STATE_REGISTERED;

Expand Down Expand Up @@ -1681,18 +1677,18 @@ int omap_hwmod_unregister(struct omap_hwmod *oh)
int omap_hwmod_enable(struct omap_hwmod *oh)
{
int r;
unsigned long flags;

if (!oh)
return -EINVAL;

mutex_lock(&oh->_mutex);
r = _omap_hwmod_enable(oh);
mutex_unlock(&oh->_mutex);
spin_lock_irqsave(&oh->_lock, flags);
r = _enable(oh);
spin_unlock_irqrestore(&oh->_lock, flags);

return r;
}


/**
* omap_hwmod_idle - idle an omap_hwmod
* @oh: struct omap_hwmod *
Expand All @@ -1702,12 +1698,14 @@ int omap_hwmod_enable(struct omap_hwmod *oh)
*/
int omap_hwmod_idle(struct omap_hwmod *oh)
{
unsigned long flags;

if (!oh)
return -EINVAL;

mutex_lock(&oh->_mutex);
_omap_hwmod_idle(oh);
mutex_unlock(&oh->_mutex);
spin_lock_irqsave(&oh->_lock, flags);
_idle(oh);
spin_unlock_irqrestore(&oh->_lock, flags);

return 0;
}
Expand All @@ -1722,12 +1720,14 @@ int omap_hwmod_idle(struct omap_hwmod *oh)
*/
int omap_hwmod_shutdown(struct omap_hwmod *oh)
{
unsigned long flags;

if (!oh)
return -EINVAL;

mutex_lock(&oh->_mutex);
spin_lock_irqsave(&oh->_lock, flags);
_shutdown(oh);
mutex_unlock(&oh->_mutex);
spin_unlock_irqrestore(&oh->_lock, flags);

return 0;
}
Expand All @@ -1740,9 +1740,11 @@ int omap_hwmod_shutdown(struct omap_hwmod *oh)
*/
int omap_hwmod_enable_clocks(struct omap_hwmod *oh)
{
mutex_lock(&oh->_mutex);
unsigned long flags;

spin_lock_irqsave(&oh->_lock, flags);
_enable_clocks(oh);
mutex_unlock(&oh->_mutex);
spin_unlock_irqrestore(&oh->_lock, flags);

return 0;
}
Expand All @@ -1755,9 +1757,11 @@ int omap_hwmod_enable_clocks(struct omap_hwmod *oh)
*/
int omap_hwmod_disable_clocks(struct omap_hwmod *oh)
{
mutex_lock(&oh->_mutex);
unsigned long flags;

spin_lock_irqsave(&oh->_lock, flags);
_disable_clocks(oh);
mutex_unlock(&oh->_mutex);
spin_unlock_irqrestore(&oh->_lock, flags);

return 0;
}
Expand Down Expand Up @@ -1801,13 +1805,14 @@ void omap_hwmod_ocp_barrier(struct omap_hwmod *oh)
int omap_hwmod_reset(struct omap_hwmod *oh)
{
int r;
unsigned long flags;

if (!oh)
return -EINVAL;

mutex_lock(&oh->_mutex);
spin_lock_irqsave(&oh->_lock, flags);
r = _reset(oh);
mutex_unlock(&oh->_mutex);
spin_unlock_irqrestore(&oh->_lock, flags);

return r;
}
Expand Down Expand Up @@ -2004,13 +2009,15 @@ int omap_hwmod_del_initiator_dep(struct omap_hwmod *oh,
*/
int omap_hwmod_enable_wakeup(struct omap_hwmod *oh)
{
unsigned long flags;

if (!oh->class->sysc ||
!(oh->class->sysc->sysc_flags & SYSC_HAS_ENAWAKEUP))
return -EINVAL;

mutex_lock(&oh->_mutex);
spin_lock_irqsave(&oh->_lock, flags);
_enable_wakeup(oh);
mutex_unlock(&oh->_mutex);
spin_unlock_irqrestore(&oh->_lock, flags);

return 0;
}
Expand All @@ -2029,13 +2036,15 @@ int omap_hwmod_enable_wakeup(struct omap_hwmod *oh)
*/
int omap_hwmod_disable_wakeup(struct omap_hwmod *oh)
{
unsigned long flags;

if (!oh->class->sysc ||
!(oh->class->sysc->sysc_flags & SYSC_HAS_ENAWAKEUP))
return -EINVAL;

mutex_lock(&oh->_mutex);
spin_lock_irqsave(&oh->_lock, flags);
_disable_wakeup(oh);
mutex_unlock(&oh->_mutex);
spin_unlock_irqrestore(&oh->_lock, flags);

return 0;
}
Expand All @@ -2055,13 +2064,14 @@ int omap_hwmod_disable_wakeup(struct omap_hwmod *oh)
int omap_hwmod_assert_hardreset(struct omap_hwmod *oh, const char *name)
{
int ret;
unsigned long flags;

if (!oh)
return -EINVAL;

mutex_lock(&oh->_mutex);
spin_lock_irqsave(&oh->_lock, flags);
ret = _assert_hardreset(oh, name);
mutex_unlock(&oh->_mutex);
spin_unlock_irqrestore(&oh->_lock, flags);

return ret;
}
Expand All @@ -2081,13 +2091,14 @@ int omap_hwmod_assert_hardreset(struct omap_hwmod *oh, const char *name)
int omap_hwmod_deassert_hardreset(struct omap_hwmod *oh, const char *name)
{
int ret;
unsigned long flags;

if (!oh)
return -EINVAL;

mutex_lock(&oh->_mutex);
spin_lock_irqsave(&oh->_lock, flags);
ret = _deassert_hardreset(oh, name);
mutex_unlock(&oh->_mutex);
spin_unlock_irqrestore(&oh->_lock, flags);

return ret;
}
Expand All @@ -2106,13 +2117,14 @@ int omap_hwmod_deassert_hardreset(struct omap_hwmod *oh, const char *name)
int omap_hwmod_read_hardreset(struct omap_hwmod *oh, const char *name)
{
int ret;
unsigned long flags;

if (!oh)
return -EINVAL;

mutex_lock(&oh->_mutex);
spin_lock_irqsave(&oh->_lock, flags);
ret = _read_hardreset(oh, name);
mutex_unlock(&oh->_mutex);
spin_unlock_irqrestore(&oh->_lock, flags);

return ret;
}
Expand Down Expand Up @@ -2180,6 +2192,7 @@ int omap_hwmod_for_each_by_class(const char *classname,
int omap_hwmod_set_postsetup_state(struct omap_hwmod *oh, u8 state)
{
int ret;
unsigned long flags;

if (!oh)
return -EINVAL;
Expand All @@ -2189,7 +2202,7 @@ int omap_hwmod_set_postsetup_state(struct omap_hwmod *oh, u8 state)
state != _HWMOD_STATE_IDLE)
return -EINVAL;

mutex_lock(&oh->_mutex);
spin_lock_irqsave(&oh->_lock, flags);

if (oh->_state != _HWMOD_STATE_REGISTERED) {
ret = -EINVAL;
Expand All @@ -2200,7 +2213,7 @@ int omap_hwmod_set_postsetup_state(struct omap_hwmod *oh, u8 state)
ret = 0;

ohsps_unlock:
mutex_unlock(&oh->_mutex);
spin_unlock_irqrestore(&oh->_lock, flags);

return ret;
}
9 changes: 2 additions & 7 deletions arch/arm/mach-omap2/serial.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -106,21 +106,16 @@ struct omap_uart_state {
static LIST_HEAD(uart_list);
static u8 num_uarts;

/*
* Since these idle/enable hooks are used in the idle path itself
* which has interrupts disabled, use the non-locking versions of
* the hwmod enable/disable functions.
*/
static int uart_idle_hwmod(struct omap_device *od)
{
_omap_hwmod_idle(od->hwmods[0]);
omap_hwmod_idle(od->hwmods[0]);

return 0;
}

static int uart_enable_hwmod(struct omap_device *od)
{
_omap_hwmod_enable(od->hwmods[0]);
omap_hwmod_enable(od->hwmods[0]);

return 0;
}
Expand Down
6 changes: 3 additions & 3 deletions arch/arm/plat-omap/include/plat/omap_hwmod.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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;
Expand Down

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