[PATCH v5 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.

Since the dependency is inside BIOS's ASL code and it's not
discoverable, so use this fixup is a hack to workaround BIOS issue.

[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>
---
v5:
 - Check CONFIG_ACPI_IPMI to fix link error.
 - Use acpi_dev_put() to balance reference count.
 - Wording.
 - Add comment to explain the rationale.

v4:
 - No change.

v3:
 - Use helper.
 - Use return value to print warning message.

v2:
 - Use completion instead of request_module().

 drivers/hwmon/acpi_power_meter.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/hwmon/acpi_power_meter.c b/drivers/hwmon/acpi_power_meter.c
index 703666b95bf4..b34cb57f2a0e 100644
--- a/drivers/hwmon/acpi_power_meter.c
+++ b/drivers/hwmon/acpi_power_meter.c
@@ -868,6 +868,9 @@ static int acpi_power_meter_add(struct acpi_device *device)
 {
 	int res;
 	struct acpi_power_meter_resource *resource;
+#if IS_REACHABLE(CONFIG_ACPI_IPMI)
+	struct acpi_device *ipi_device;
+#endif
 
 	if (!device)
 		return -EINVAL;
@@ -883,6 +886,24 @@ static int acpi_power_meter_add(struct acpi_device *device)
 	strcpy(acpi_device_class(device), ACPI_POWER_METER_CLASS);
 	device->driver_data = resource;
 
+#if IS_REACHABLE(CONFIG_ACPI_IPMI)
+	/*
+	 * On Dell systems several methods of acpi_power_meter access
+	 * variables in IPMI region, 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.
+	 */
+	if (dmi_match(DMI_SYS_VENDOR, "Dell Inc.")) {
+		ipi_device = acpi_dev_get_first_match_dev("IPI0001", NULL, -1);
+
+		if (ipi_device) {
+			if (acpi_wait_for_acpi_ipmi())
+				dev_warn(&device->dev, "Waiting for ACPI IPMI timeout");
+			acpi_dev_put(ipi_device);
+		}
+	}
+#endif
+
 	res = read_capabilities(resource);
 	if (res)
 		goto exit_free;
-- 
2.34.1