[PATCH] platform/x86: thinkpad_acpi: Fix fan speed reporting on ThinkPad L440

[Daniel Salmun]

The L440 (BIOS J4ET93WW) reports its fan as stopped: /proc/acpi/ibm/fan
shows "status: disabled" and "speed: 0", and hwmon fan1_input is 0 under
any load. EC registers 0x2F and 0x84/0x85 always read 0 on this model.

The EC uses the 0x93/0x95 layout handled by TPACPI_FAN_NS. 0x93 reads 4
(FAN_NS_CTRL_STATUS) and 0x95 goes from 255 at idle to about 111 at full
speed. The DSDT has no fan methods.

Add model ID "J4" to fan_quirk_table. The fan then reads about 1900 RPM
at idle and 2900 RPM under load.

Tested on a ThinkPad L440 20ASS20200 with BIOS J4ET93WW and EC J4HT30WW.

Link: https://github.com/lm-sensors/lm-sensors/issues/510
Signed-off-by: Daniel Salmun <salmundani@xxxxxxxxx>
---
Manual fan control works on this EC (0x93 = 0x14, target written to
0x94) but is not part of this patch.

I have not checked FAN_RPM_CAL_CONST against a real tachometer. With it
the range is 1927-4428 RPM, which fits the 5 V blower in this machine.

The L540 uses the same EC firmware and probably needs the same entry,
but I don't have one to check its model ID.

 drivers/platform/x86/lenovo/thinkpad_acpi.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/platform/x86/lenovo/thinkpad_acpi.c b/drivers/platform/x86/lenovo/thinkpad_acpi.c
index 1661f070c..c63e54eaa 100644
--- a/drivers/platform/x86/lenovo/thinkpad_acpi.c
+++ b/drivers/platform/x86/lenovo/thinkpad_acpi.c
@@ -8846,6 +8846,7 @@ static const struct tpacpi_quirk fan_quirk_table[] __initconst = {
 	TPACPI_Q_LNV3('R', '1', 'D', TPACPI_FAN_NS),	/* 11e Gen5 GL-R */
 	TPACPI_Q_LNV3('R', '0', 'V', TPACPI_FAN_NS),	/* 11e Gen5 KL-Y */
 	TPACPI_Q_LNV('H', '3', TPACPI_FAN_NS),		/* Edge E330 */
+	TPACPI_Q_LNV('J', '4', TPACPI_FAN_NS),		/* L440 */
 	TPACPI_Q_LNV3('N', '1', 'O', TPACPI_FAN_NOFAN),	/* X1 Tablet (2nd gen) */
 	TPACPI_Q_LNV3('R', '0', 'Q', TPACPI_FAN_DECRPM),/* L480 */
 	TPACPI_Q_LNV('8', 'F', TPACPI_FAN_TPR),		/* ThinkPad x120e */

base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
-- 
2.34.1