[PATCH] platform/x86: thinkpad_acpi: Fix Embedded Controller access on X380 Yoga

[Daniel Bertalan <dani@danielbertalan.dev>]

On the X380 Yoga, the `ECRD` and `ECWR` ACPI objects cannot be used for
accessing the Embedded Controller: instead of a method that reads from
the EC's memory, `ECRD` is the name of a location in high memory. This
meant that trying to call them would fail with the following message:

  ACPI: \_SB.PCI0.LPCB.EC.ECRD: 1 arguments were passed to a non-method
  ACPI object (RegionField)

With this commit, it is now possible to access the EC and read
temperature and fan speed information. Note that while writes to the
HFSP register do go through (as indicated by subsequent reads showing
the new value), the fan does not actually change its speed.

Signed-off-by: Daniel Bertalan <dani@danielbertalan.dev>
---
 drivers/platform/x86/thinkpad_acpi.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index 7191ff2625b1..6fe82f805ea8 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -11699,6 +11699,7 @@ static int __init thinkpad_acpi_module_init(void)
 {
 	const struct dmi_system_id *dmi_id;
 	int ret, i;
+	acpi_object_type obj_type;
 
 	tpacpi_lifecycle = TPACPI_LIFE_INIT;
 
@@ -11724,6 +11725,21 @@ static int __init thinkpad_acpi_module_init(void)
 	TPACPI_ACPIHANDLE_INIT(ecrd);
 	TPACPI_ACPIHANDLE_INIT(ecwr);
 
+	/*
+	 * Quirk: in some models (e.g. X380 Yoga), an object named ECRD
+	 * exists, but it is a register, not a method.
+	 */
+	if (ecrd_handle) {
+		acpi_get_type(ecrd_handle, &obj_type);
+		if (obj_type != ACPI_TYPE_METHOD)
+			ecrd_handle = NULL;
+	}
+	if (ecwr_handle) {
+		acpi_get_type(ecwr_handle, &obj_type);
+		if (obj_type != ACPI_TYPE_METHOD)
+			ecwr_handle = NULL;
+	}
+
 	tpacpi_wq = create_singlethread_workqueue(TPACPI_WORKQUEUE_NAME);
 	if (!tpacpi_wq) {
 		thinkpad_acpi_module_exit();
-- 
2.40.0