OPP: Allow notifiers to call dev_pm_opp_get_{voltage, freq} RCU-free

We pass the dev_pm_opp structure to OPP notifiers but the users
of the notifier need to surround calls to dev_pm_opp_get_*() with
RCU read locks to avoid lockdep warnings. The notifier is already
called with the dev_opp's srcu lock held, so it should be safe to
assume the devm_pm_opp structure is already protected inside the
notifier. Update the lockdep check for this.

Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
index c43111dde387b7070e2e3e4f68c1be8a165d2c47..d2ce16bbd1cf21f04cb3c12a26084d992f00c2a8 100644 (file)
--- a/drivers/base/power/opp/core.c
+++ b/drivers/base/power/opp/core.c
@@ -31,9 +31,10 @@ static LIST_HEAD(dev_opp_list);
 /* Lock to allow exclusive modification to the device and opp lists */
 DEFINE_MUTEX(dev_opp_list_lock);
 
-#define opp_rcu_lockdep_assert()                                       \
+#define opp_rcu_lockdep_assert(s)                                      \
 do {                                                                   \
        RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&                       \
+                               !(s && srcu_read_lock_held(s)) &&       \
                                !lockdep_is_held(&dev_opp_list_lock),   \
                           "Missing rcu_read_lock() or "                \
                           "dev_opp_list_lock protection");             \
@@ -91,7 +92,7 @@ struct device_opp *_find_device_opp(struct device *dev)
 {
        struct device_opp *dev_opp;
 
-       opp_rcu_lockdep_assert();
+       opp_rcu_lockdep_assert(NULL);
 
        if (IS_ERR_OR_NULL(dev)) {
                pr_err("%s: Invalid parameters\n", __func__);
@@ -125,10 +126,11 @@ unsigned long dev_pm_opp_get_voltage(struct dev_pm_opp *opp)
        struct dev_pm_opp *tmp_opp;
        unsigned long v = 0;
 
-       opp_rcu_lockdep_assert();
+       opp_rcu_lockdep_assert(&opp->dev_opp->srcu_head.srcu);
 
-       tmp_opp = rcu_dereference(opp);
-       if (IS_ERR_OR_NULL(tmp_opp))
+       tmp_opp = srcu_dereference_check(opp, &opp->dev_opp->srcu_head.srcu,
+                                        rcu_read_lock_held());
+       if (IS_ERR_OR_NULL(tmp_opp) || !tmp_opp->available)
                pr_err("%s: Invalid parameters\n", __func__);
        else
                v = tmp_opp->u_volt;
@@ -157,9 +159,10 @@ unsigned long dev_pm_opp_get_freq(struct dev_pm_opp *opp)
        struct dev_pm_opp *tmp_opp;
        unsigned long f = 0;
 
-       opp_rcu_lockdep_assert();
+       opp_rcu_lockdep_assert(&opp->dev_opp->srcu_head.srcu);
 
-       tmp_opp = rcu_dereference(opp);
+       tmp_opp = srcu_dereference_check(opp, &opp->dev_opp->srcu_head.srcu,
+                                        rcu_read_lock_held());
        if (IS_ERR_OR_NULL(tmp_opp) || !tmp_opp->available)
                pr_err("%s: Invalid parameters\n", __func__);
        else
@@ -191,7 +194,7 @@ bool dev_pm_opp_is_turbo(struct dev_pm_opp *opp)
 {
        struct dev_pm_opp *tmp_opp;
 
-       opp_rcu_lockdep_assert();
+       opp_rcu_lockdep_assert(&opp->dev_opp->srcu_head.srcu);
 
        tmp_opp = rcu_dereference(opp);
        if (IS_ERR_OR_NULL(tmp_opp) || !tmp_opp->available) {
@@ -246,7 +249,7 @@ struct dev_pm_opp *dev_pm_opp_get_suspend_opp(struct device *dev)
 {
        struct device_opp *dev_opp;
 
-       opp_rcu_lockdep_assert();
+       opp_rcu_lockdep_assert(NULL);
 
        dev_opp = _find_device_opp(dev);
        if (IS_ERR(dev_opp) || !dev_opp->suspend_opp ||
@@ -326,7 +329,7 @@ struct dev_pm_opp *dev_pm_opp_find_freq_exact(struct device *dev,
        struct device_opp *dev_opp;
        struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);
 
-       opp_rcu_lockdep_assert();
+       opp_rcu_lockdep_assert(NULL);
 
        dev_opp = _find_device_opp(dev);
        if (IS_ERR(dev_opp)) {
@@ -374,7 +377,7 @@ struct dev_pm_opp *dev_pm_opp_find_freq_ceil(struct device *dev,
        struct device_opp *dev_opp;
        struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);
 
-       opp_rcu_lockdep_assert();
+       opp_rcu_lockdep_assert(NULL);
 
        if (!dev || !freq) {
                dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
@@ -424,7 +427,7 @@ struct dev_pm_opp *dev_pm_opp_find_freq_floor(struct device *dev,
        struct device_opp *dev_opp;
        struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);
 
-       opp_rcu_lockdep_assert();
+       opp_rcu_lockdep_assert(NULL);
 
        if (!dev || !freq) {
                dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);