[PATCH v2] hwmon: (acpi_power_meter) Ensure IPMI space handler is ready on Dell systems

[Kai-Heng Feng]

The following error can be observed at boot:
[    3.717920] ACPI Error: No handler for Region [SYSI] (00000000ab9e62c5) [IPMI] (20230628/evregion-130)
[    3.717928] ACPI Error: Region IPMI (ID=7) has no handler (20230628/exfldio-261)

[    3.717936] No Local Variables are initialized for Method [_GHL]

[    3.717938] No Arguments are initialized for method [_GHL]

[    3.717940] ACPI Error: Aborting method \_SB.PMI0._GHL due to previous error (AE_NOT_EXIST) (20230628/psparse-529)
[    3.717949] ACPI Error: Aborting method \_SB.PMI0._PMC due to previous error (AE_NOT_EXIST) (20230628/psparse-529)
[    3.717957] ACPI: \_SB_.PMI0: _PMC evaluation failed: AE_NOT_EXIST

On Dell systems several methods of acpi_power_meter access variables in
IPMI region [0], so wait until IPMI space handler is installed by
acpi_ipmi and also wait until SMI is selected to make the space handler
fully functional.

[0] https://www.dell.com/support/manuals/en-us/redhat-enterprise-linux-v8.0/rhel8_rn_pub/advanced-configuration-and-power-interface-acpi-error-messages-displayed-in-dmesg?guid=guid-0d5ae482-1977-42cf-b417-3ed5c3f5ee62

Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
---
v2:
 - Use completion instead of request_module().

 drivers/acpi/acpi_ipmi.c         | 13 ++++++++++++-
 drivers/hwmon/acpi_power_meter.c |  4 ++++
 include/acpi/acpi_bus.h          |  4 ++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/acpi_ipmi.c b/drivers/acpi/acpi_ipmi.c
index 0555f68c2dfd..2ea8b7e6cebf 100644
--- a/drivers/acpi/acpi_ipmi.c
+++ b/drivers/acpi/acpi_ipmi.c
@@ -23,6 +23,8 @@ MODULE_LICENSE("GPL");
 #define IPMI_TIMEOUT			(5000)
 #define ACPI_IPMI_MAX_MSG_LENGTH	64
 
+static struct completion smi_selected;
+
 struct acpi_ipmi_device {
 	/* the device list attached to driver_data.ipmi_devices */
 	struct list_head head;
@@ -463,8 +465,10 @@ static void ipmi_register_bmc(int iface, struct device *dev)
 		if (temp->handle == handle)
 			goto err_lock;
 	}
-	if (!driver_data.selected_smi)
+	if (!driver_data.selected_smi) {
 		driver_data.selected_smi = ipmi_device;
+		complete(&smi_selected);
+	}
 	list_add_tail(&ipmi_device->head, &driver_data.ipmi_devices);
 	mutex_unlock(&driver_data.ipmi_lock);
 
@@ -578,10 +582,17 @@ acpi_ipmi_space_handler(u32 function, acpi_physical_address address,
 	return status;
 }
 
+void wait_for_acpi_ipmi(void)
+{
+	wait_for_completion_interruptible_timeout(&smi_selected, 2 * HZ);
+}
+EXPORT_SYMBOL_GPL(wait_for_acpi_ipmi);
+
 static int __init acpi_ipmi_init(void)
 {
 	int result;
 	acpi_status status;
+	init_completion(&smi_selected);
 
 	if (acpi_disabled)
 		return 0;
diff --git a/drivers/hwmon/acpi_power_meter.c b/drivers/hwmon/acpi_power_meter.c
index 703666b95bf4..acaf1ae68dc8 100644
--- a/drivers/hwmon/acpi_power_meter.c
+++ b/drivers/hwmon/acpi_power_meter.c
@@ -883,6 +883,10 @@ static int acpi_power_meter_add(struct acpi_device *device)
 	strcpy(acpi_device_class(device), ACPI_POWER_METER_CLASS);
 	device->driver_data = resource;
 
+	if (dmi_match(DMI_SYS_VENDOR, "Dell Inc.") &&
+	    acpi_dev_get_first_match_dev("IPI0001", NULL, -1))
+		wait_for_acpi_ipmi();
+
 	res = read_capabilities(resource);
 	if (res)
 		goto exit_free;
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 1216d72c650f..ed59fb89721e 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -655,6 +655,7 @@ bool acpi_device_override_status(struct acpi_device *adev, unsigned long long *s
 bool acpi_quirk_skip_acpi_ac_and_battery(void);
 int acpi_install_cmos_rtc_space_handler(acpi_handle handle);
 void acpi_remove_cmos_rtc_space_handler(acpi_handle handle);
+void wait_for_acpi_ipmi(void);
 #else
 static inline bool acpi_device_override_status(struct acpi_device *adev,
 					       unsigned long long *status)
@@ -672,6 +673,9 @@ static inline int acpi_install_cmos_rtc_space_handler(acpi_handle handle)
 static inline void acpi_remove_cmos_rtc_space_handler(acpi_handle handle)
 {
 }
+static inline void wait_for_acpi_ipmi(void)
+{
+}
 #endif
 
 #if IS_ENABLED(CONFIG_X86_ANDROID_TABLETS)
-- 
2.34.1