platform/x86: thinkpad_acpi: Add dual fan probe

Instead of having quirks for systems that have a second fan it would
be nice to detect this setup.
Unfortunately, confirmed by the Lenovo FW team, there is no way to
retrieve this information from the EC or BIOS. Recommendation was to
attempt to read the fan and if successful then assume a 2nd fan is
present.

The fans are also supposed to spin up on boot for some time, so in
theory we could check for a speed > 0. In testing this seems to hold
true but as I couldn't test on all platforms I've avoided implementing
this. It also breaks for the corner case where you load the module
once the fans are idle.

Tested on P1G4, P1G3, X1C9 and T14 (no fans) and it works correctly.
For the platforms with dual fans where it was confirmed to work I have
removed the quirks. Potentially this could be done for all platforms
but I've left untested platforms in for now. On these platforms the
fans will be enabled and then detected - so no impact.
Signed-off-by: Mark Pearson <markpearson@lenovo.com>
Link: https://lore.kernel.org/r/20220222185137.4325-1-markpearson@lenovo.comReviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/thinkpad_acpi.c

@@ -8698,10 +8698,7 @@ static const struct tpacpi_quirk fan_quirk_table[] __initconst = {
 	TPACPI_Q_LNV3('N', '2', 'N', TPACPI_FAN_2CTL),	/* P53 / P73 */
 	TPACPI_Q_LNV3('N', '2', 'E', TPACPI_FAN_2CTL),	/* P1 / X1 Extreme (1st gen) */
 	TPACPI_Q_LNV3('N', '2', 'O', TPACPI_FAN_2CTL),	/* P1 / X1 Extreme (2nd gen) */
-	TPACPI_Q_LNV3('N', '2', 'V', TPACPI_FAN_2CTL),	/* P1 / X1 Extreme (3nd gen) */
-	TPACPI_Q_LNV3('N', '4', '0', TPACPI_FAN_2CTL),	/* P1 / X1 Extreme (4nd gen) */
 	TPACPI_Q_LNV3('N', '3', '0', TPACPI_FAN_2CTL),	/* P15 (1st gen) / P15v (1st gen) */
-	TPACPI_Q_LNV3('N', '3', '2', TPACPI_FAN_2CTL),	/* X1 Carbon (9th gen) */
 	TPACPI_Q_LNV3('N', '3', '7', TPACPI_FAN_2CTL),  /* T15g (2nd gen) */
 	TPACPI_Q_LNV3('N', '1', 'O', TPACPI_FAN_NOFAN),	/* X1 Tablet (2nd gen) */
 };
@@ -8745,6 +8742,9 @@ static int __init fan_init(struct ibm_init_struct *iibm)
 		 * ThinkPad ECs supports the fan control register */
 		if (likely(acpi_ec_read(fan_status_offset,
 					&fan_control_initial_status))) {
+			int res;
+			unsigned int speed;
+
 			fan_status_access_mode = TPACPI_FAN_RD_TPEC;
 			if (quirks & TPACPI_FAN_Q1)
 				fan_quirk1_setup();
@@ -8757,6 +8757,15 @@ static int __init fan_init(struct ibm_init_struct *iibm)
 				tp_features.second_fan_ctl = 1;
 				pr_info("secondary fan control enabled\n");
 			}
+			/* Try and probe the 2nd fan */
+			res = fan2_get_speed(&speed);
+			if (res >= 0) {
+				/* It responded - so let's assume it's there */
+				tp_features.second_fan = 1;
+				tp_features.second_fan_ctl = 1;
+				pr_info("secondary fan control detected & enabled\n");
+			}
+
 		} else {
 			pr_err("ThinkPad ACPI EC access misbehaving, fan status and control unavailable\n");
 			return -ENODEV;