[PATCH v3 2/2] hwmon: (acpi_power_meter) Ensure IPMI space handler is ready on Dell systems

[Kai-Heng Feng <kai.heng.feng@canonical.com>]

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@canonical.com>
---
v3:
 - Use helper.
 - Use return value to print warning message.

v2:
 - Use completion instead of request_module().

 drivers/hwmon/acpi_power_meter.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/hwmon/acpi_power_meter.c b/drivers/hwmon/acpi_power_meter.c
index 703666b95bf4..33fb9626633d 100644
--- a/drivers/hwmon/acpi_power_meter.c
+++ b/drivers/hwmon/acpi_power_meter.c
@@ -883,6 +883,12 @@ 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)) {
+		if (acpi_wait_for_acpi_ipmi())
+			dev_warn(&device->dev, "Waiting for ACPI IPMI timeout");
+	}
+
 	res = read_capabilities(resource);
 	if (res)
 		goto exit_free;
-- 
2.34.1