[PATCH 2/7] ARM: OMAP2+: PM: add a lock to protect the powerdomains next state

[Jean Pihet]

pwrdm_set_fpwrst, pwrdm_set_next_fpwrst and pwrdm_read_next_fpwrst
are intented to be the only API to program and request the next
state of a power domain.
This patch protects the power domain next state settings and structs
from concurrent accesses by the use of a lock.

A spinlock is used since the API functions can be called from
atomic context (.i.e) either from cpuidle path or suspend path.

[ambresh at ti.com: reported the atomic context issue and suggested
to replace the initial mutex with a spinlock]

Signed-off-by: Jean Pihet <j-pihet at ti.com>
Reported-by: Ambresh K <ambresh at ti.com>
---
 arch/arm/mach-omap2/powerdomain.c |   40 ++++++++++++++++++++++++++++++++----
 arch/arm/mach-omap2/powerdomain.h |    3 ++
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/arch/arm/mach-omap2/powerdomain.c b/arch/arm/mach-omap2/powerdomain.c
index 18c21fa..f4b219f 100644
--- a/arch/arm/mach-omap2/powerdomain.c
+++ b/arch/arm/mach-omap2/powerdomain.c
@@ -102,6 +102,7 @@ static int _pwrdm_register(struct powerdomain *pwrdm)
 	INIT_LIST_HEAD(&pwrdm->voltdm_node);
 	voltdm_add_pwrdm(voltdm, pwrdm);
 
+	spin_lock_init(&pwrdm->lock);
 	list_add(&pwrdm->node, &pwrdm_list);
 
 	/* Initialize the powerdomain's state counter */
@@ -394,6 +395,22 @@ static int _pwrdm_pwrst_to_fpwrst(struct powerdomain *pwrdm, u8 pwrst, u8 logic)
 }
 
 
+/**
+ * _pwrdm_read_next_fpwrst - get next powerdomain functional power state
+ * @pwrdm: struct powerdomain * to get power state
+ *
+ * Return the powerdomain @pwrdm's next functional power state.
+ * Returns -EINVAL if the powerdomain pointer is null or returns
+ * the next power state upon success.
+ */
+static int _pwrdm_read_next_fpwrst(struct powerdomain *pwrdm)
+{
+	int next_pwrst = pwrdm_read_next_pwrst(pwrdm);
+	int next_logic = pwrdm_read_logic_retst(pwrdm);
+
+	return _pwrdm_pwrst_to_fpwrst(pwrdm, next_pwrst, next_logic);
+}
+
 /* Public functions */
 
 /**
@@ -677,6 +694,7 @@ int pwrdm_set_fpwrst(struct powerdomain *pwrdm, enum pwrdm_func_state fpwrst)
 	int pwrst = _pwrdm_fpwrst_to_pwrst(pwrdm, fpwrst);
 	int logic = _pwrdm_fpwrst_to_logic_pwrst(pwrdm, fpwrst);
 	int sleep_switch = -1, ret = 0, hwsup = 0;
+	unsigned long flags;
 
 	if (!pwrdm || IS_ERR(pwrdm) || (pwrst < 0) || (logic < 0)) {
 		pr_debug("%s: invalid params: pwrdm=%p, fpwrst=%0x\n",
@@ -687,9 +705,11 @@ int pwrdm_set_fpwrst(struct powerdomain *pwrdm, enum pwrdm_func_state fpwrst)
 	pr_debug("%s: set fpwrst %0x to pwrdm %s\n",
 		 __func__, fpwrst, pwrdm->name);
 
-	next_fpwrst = pwrdm_read_next_fpwrst(pwrdm);
+	spin_lock_irqsave(&pwrdm->lock, flags);
+
+	next_fpwrst = _pwrdm_read_next_fpwrst(pwrdm);
 	if (next_fpwrst == fpwrst)
-		return ret;
+		goto out;
 
 	curr_pwrst = pwrdm_read_pwrst(pwrdm);
 	if (curr_pwrst < PWRDM_POWER_ON) {
@@ -725,6 +745,8 @@ int pwrdm_set_fpwrst(struct powerdomain *pwrdm, enum pwrdm_func_state fpwrst)
 		break;
 	}
 
+out:
+	spin_unlock_irqrestore(&pwrdm->lock, flags);
 	return ret;
 }
 
@@ -741,6 +763,7 @@ int pwrdm_set_next_fpwrst(struct powerdomain *pwrdm,
 	int pwrst = _pwrdm_fpwrst_to_pwrst(pwrdm, fpwrst);
 	int logic = _pwrdm_fpwrst_to_logic_pwrst(pwrdm, fpwrst);
 	int ret = 0;
+	unsigned long flags;
 
 	if (!pwrdm || IS_ERR(pwrdm) || (pwrst < 0) || (logic < 0)) {
 		pr_debug("%s: invalid params: pwrdm=%p, fpwrst=%0x\n",
@@ -751,6 +774,8 @@ int pwrdm_set_next_fpwrst(struct powerdomain *pwrdm,
 	pr_debug("%s: set fpwrst %0x to pwrdm %s\n",
 		 __func__, fpwrst, pwrdm->name);
 
+	spin_lock_irqsave(&pwrdm->lock, flags);
+
 	ret = pwrdm_set_logic_retst(pwrdm, logic);
 	if (ret)
 		pr_err("%s: unable to set logic state %0x of powerdomain: %s\n",
@@ -761,6 +786,7 @@ int pwrdm_set_next_fpwrst(struct powerdomain *pwrdm,
 		pr_err("%s: unable to set power state %0x of powerdomain: %s\n",
 		       __func__, pwrst, pwrdm->name);
 
+	spin_unlock_irqrestore(&pwrdm->lock, flags);
 	return ret;
 };
 
@@ -837,10 +863,14 @@ int pwrdm_read_next_pwrst(struct powerdomain *pwrdm)
  */
 int pwrdm_read_next_fpwrst(struct powerdomain *pwrdm)
 {
-	int next_pwrst = pwrdm_read_next_pwrst(pwrdm);
-	int next_logic = pwrdm_read_logic_retst(pwrdm);
+	int ret;
+	unsigned long flags;
 
-	return _pwrdm_pwrst_to_fpwrst(pwrdm, next_pwrst, next_logic);
+	spin_lock_irqsave(&pwrdm->lock, flags);
+	ret = _pwrdm_read_next_fpwrst(pwrdm);
+	spin_unlock_irqrestore(&pwrdm->lock, flags);
+
+	return ret;
 }
 
 /**
diff --git a/arch/arm/mach-omap2/powerdomain.h b/arch/arm/mach-omap2/powerdomain.h
index aa5de4f..c3dc363 100644
--- a/arch/arm/mach-omap2/powerdomain.h
+++ b/arch/arm/mach-omap2/powerdomain.h
@@ -17,6 +17,7 @@
 #include <linux/types.h>
 #include <linux/list.h>
 
+#include <linux/spinlock.h>
 #include <linux/atomic.h>
 
 #include <plat/cpu.h>
@@ -109,6 +110,7 @@ struct powerdomain;
  * @pwrdm_clkdms: Clockdomains in this powerdomain
  * @node: list_head linking all powerdomains
  * @voltdm_node: list_head linking all powerdomains in a voltagedomain
+ * @lock: powerdomain next state registers protection lock
  * @pwrstctrl_offs: (AM33XX only) XXX_PWRSTCTRL reg offset from prcm_offs
  * @pwrstst_offs: (AM33XX only) XXX_PWRSTST reg offset from prcm_offs
  * @logicretstate_mask: (AM33XX only) mask for logic retention bitfield
@@ -142,6 +144,7 @@ struct powerdomain {
 	struct clockdomain *pwrdm_clkdms[PWRDM_MAX_CLKDMS];
 	struct list_head node;
 	struct list_head voltdm_node;
+	spinlock_t lock;
 	int state;
 	unsigned state_counter[PWRDM_MAX_PWRSTS];
 	unsigned ret_logic_off_counter;
-- 
1.7.7.6