x86/platform/intel/iosf_mbi: Add unlocked PMIC bus access notifier unregister

For race free unregistration drivers may need to acquire PMIC bus access
through iosf_mbi_punit_acquire() and then (un)register the notifier without
dropping the lock.

This commit adds an unlocked variant of
iosf_mbi_unregister_pmic_bus_access_notifier for this use case.

Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171019111620.26761-2-hdegoede@redhat.com

diff --git a/arch/x86/include/asm/iosf_mbi.h b/arch/x86/include/asm/iosf_mbi.h
index c313cac36f564ab0d9b57d618ff8cc7de33debef..eb959cd77994f1f3096bedf30518ff773b6ceeb8 100644 (file)
--- a/arch/x86/include/asm/iosf_mbi.h
+++ b/arch/x86/include/asm/iosf_mbi.h
@@ -145,6 +145,18 @@ int iosf_mbi_register_pmic_bus_access_notifier(struct notifier_block *nb);
  */
 int iosf_mbi_unregister_pmic_bus_access_notifier(struct notifier_block *nb);
 
+/**
+ * iosf_mbi_unregister_pmic_bus_access_notifier_unlocked - Unregister PMIC bus
+ *                                                         notifier, unlocked
+ *
+ * Like iosf_mbi_unregister_pmic_bus_access_notifier(), but for use when the
+ * caller has already called iosf_mbi_punit_acquire() itself.
+ *
+ * @nb: notifier_block to unregister
+ */
+int iosf_mbi_unregister_pmic_bus_access_notifier_unlocked(
+       struct notifier_block *nb);
+
 /**
  * iosf_mbi_call_pmic_bus_access_notifier_chain - Call PMIC bus notifier chain
  *
@@ -153,6 +165,11 @@ int iosf_mbi_unregister_pmic_bus_access_notifier(struct notifier_block *nb);
  */
 int iosf_mbi_call_pmic_bus_access_notifier_chain(unsigned long val, void *v);
 
+/**
+ * iosf_mbi_assert_punit_acquired - Assert that the P-Unit has been acquired.
+ */
+void iosf_mbi_assert_punit_acquired(void);
+
 #else /* CONFIG_IOSF_MBI is not enabled */
 static inline
 bool iosf_mbi_available(void)
@@ -196,12 +213,20 @@ int iosf_mbi_unregister_pmic_bus_access_notifier(struct notifier_block *nb)
        return 0;
 }
 
+static inline int
+iosf_mbi_unregister_pmic_bus_access_notifier_unlocked(struct notifier_block *nb)
+{
+       return 0;
+}
+
 static inline
 int iosf_mbi_call_pmic_bus_access_notifier_chain(unsigned long val, void *v)
 {
        return 0;
 }
 
+static inline void iosf_mbi_assert_punit_acquired(void) {}
+
 #endif /* CONFIG_IOSF_MBI */
 
 #endif /* IOSF_MBI_SYMS_H */

diff --git a/arch/x86/platform/intel/iosf_mbi.c b/arch/x86/platform/intel/iosf_mbi.c
index a952ac199741401a5ea085cce623325f8f52b4ec..6f37a2137a79519c7e55382bf80f1eb098931bbb 100644 (file)
--- a/arch/x86/platform/intel/iosf_mbi.c
+++ b/arch/x86/platform/intel/iosf_mbi.c
@@ -218,14 +218,23 @@ int iosf_mbi_register_pmic_bus_access_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL(iosf_mbi_register_pmic_bus_access_notifier);
 
+int iosf_mbi_unregister_pmic_bus_access_notifier_unlocked(
+       struct notifier_block *nb)
+{
+       iosf_mbi_assert_punit_acquired();
+
+       return blocking_notifier_chain_unregister(
+                               &iosf_mbi_pmic_bus_access_notifier, nb);
+}
+EXPORT_SYMBOL(iosf_mbi_unregister_pmic_bus_access_notifier_unlocked);
+
 int iosf_mbi_unregister_pmic_bus_access_notifier(struct notifier_block *nb)
 {
        int ret;
 
        /* Wait for the bus to go inactive before unregistering */
        mutex_lock(&iosf_mbi_punit_mutex);
-       ret = blocking_notifier_chain_unregister(
-                               &iosf_mbi_pmic_bus_access_notifier, nb);
+       ret = iosf_mbi_unregister_pmic_bus_access_notifier_unlocked(nb);
        mutex_unlock(&iosf_mbi_punit_mutex);
 
        return ret;
@@ -239,6 +248,12 @@ int iosf_mbi_call_pmic_bus_access_notifier_chain(unsigned long val, void *v)
 }
 EXPORT_SYMBOL(iosf_mbi_call_pmic_bus_access_notifier_chain);
 
+void iosf_mbi_assert_punit_acquired(void)
+{
+       WARN_ON(!mutex_is_locked(&iosf_mbi_punit_mutex));
+}
+EXPORT_SYMBOL(iosf_mbi_assert_punit_acquired);
+
 #ifdef CONFIG_IOSF_MBI_DEBUG
 static u32     dbg_mdr;
 static u32     dbg_mcr;