Merge tag 'acpi-4.20-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull more ACPI updates from Rafael Wysocki:
 "Rework the handling of the P-unit semaphore on Intel Baytrail and
  Cherrytrail systems to avoid race conditions and excessive overhead
  related to it (Hans de Goede)"

* tag 'acpi-4.20-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  ACPI / PMIC: xpower: Add depends on IOSF_MBI to Kconfig entry
  i2c: designware: Cleanup bus lock handling
  ACPI / PMIC: xpower: Block P-Unit I2C access during read-modify-write
  x86: baytrail/cherrytrail: Rework and move P-Unit PMIC bus semaphore code

1 files changed, 29 insertions, 10 deletions

diff --git a/arch/x86/include/asm/iosf_mbi.h b/arch/x86/include/asm/iosf_mbi.h
index 3de0489deade..5270ff39b9af 100644
--- a/arch/x86/include/asm/iosf_mbi.h
+++ b/arch/x86/include/asm/iosf_mbi.h
@@ -105,8 +105,10 @@ int iosf_mbi_modify(u8 port, u8 opcode, u32 offset, u32 mdr, u32 mask);
  * the PMIC bus while another driver is also accessing the PMIC bus various bad
  * things happen.
  *
- * To avoid these problems this function must be called before accessing the
- * P-Unit or the PMIC, be it through iosf_mbi* functions or through other means.
+ * Call this function before sending requests to the P-Unit which may make it
+ * access the PMIC, be it through iosf_mbi* functions or through other means.
+ * This function will block all kernel access to the PMIC I2C bus, so that the
+ * P-Unit can safely access the PMIC over the shared I2C bus.
  *
  * Note on these systems the i2c-bus driver will request a sempahore from the
  * P-Unit for exclusive access to the PMIC bus when i2c drivers are accessing
@@ -123,6 +125,31 @@ void iosf_mbi_punit_acquire(void);
 void iosf_mbi_punit_release(void);
 
 /**
+ * iosf_mbi_block_punit_i2c_access() - Block P-Unit accesses to the PMIC bus
+ *
+ * Call this function to block P-Unit access to the PMIC I2C bus, so that the
+ * kernel can safely access the PMIC over the shared I2C bus.
+ *
+ * This function acquires the P-Unit bus semaphore and notifies
+ * pmic_bus_access_notifier listeners that they may no longer access the
+ * P-Unit in a way which may cause it to access the shared I2C bus.
+ *
+ * Note this function may be called multiple times and the bus will not
+ * be released until iosf_mbi_unblock_punit_i2c_access() has been called the
+ * same amount of times.
+ *
+ * Return: Nonzero on error
+ */
+int iosf_mbi_block_punit_i2c_access(void);
+
+/*
+ * iosf_mbi_unblock_punit_i2c_access() - Release PMIC I2C bus block
+ *
+ * Release i2c access block gotten through iosf_mbi_block_punit_i2c_access().
+ */
+void iosf_mbi_unblock_punit_i2c_access(void);
+
+/**
  * iosf_mbi_register_pmic_bus_access_notifier - Register PMIC bus notifier
  *
  * This function can be used by drivers which may need to acquire P-Unit
@@ -159,14 +186,6 @@ 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
- *
- * @val: action to pass into listener's notifier_call function
- * @v: data pointer to pass into listener's notifier_call function
- */
-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);