platform/x86: thinkpad_acpi: Implement tablet mode using GMMS method

Many thinkpad laptops and convertibles provide the GMMS method to
resolve how far the laptop has been opened and whether it has been
converted into tablet mode. This allows reporting a more precise tablet
mode state to userspace.

The current implementation only reports a summarized tablet mode state
which is triggered as soon as the input devices become unusable as they
are folded away from the display.

This will work on all models where the CMMD method was used previously and
it may also work in other cases.

Thanks to Peter Zhang of Lenovo for providing information on how to use the
GMMS method to query the tablet mode.

Signed-off-by: Benjamin Berg <bberg@redhat.com>
Cc: Peter FP1 Zhang <zhangfp1@lenovo.com>
Cc: Lyude Paul <lyude@redhat.com>
Acked-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/thinkpad_acpi.c

@@ -310,8 +310,7 @@ static struct {
 	enum {
 		TP_HOTKEY_TABLET_NONE = 0,
 		TP_HOTKEY_TABLET_USES_MHKG,
-		/* X1 Yoga 2016, seen on BIOS N1FET44W */
-		TP_HOTKEY_TABLET_USES_CMMD,
+		TP_HOTKEY_TABLET_USES_GMMS,
 	} hotkey_tablet;
 	u32 kbdlight:1;
 	u32 light:1;
@@ -2044,8 +2043,28 @@ static void hotkey_poll_setup(const bool may_warn);
 
 /* HKEY.MHKG() return bits */
 #define TP_HOTKEY_TABLET_MASK (1 << 3)
-/* ThinkPad X1 Yoga (2016) */
-#define TP_EC_CMMD_TABLET_MODE 0x6
+enum {
+	TP_ACPI_MULTI_MODE_INVALID	= 0,
+	TP_ACPI_MULTI_MODE_UNKNOWN	= 1 << 0,
+	TP_ACPI_MULTI_MODE_LAPTOP	= 1 << 1,
+	TP_ACPI_MULTI_MODE_TABLET	= 1 << 2,
+	TP_ACPI_MULTI_MODE_FLAT		= 1 << 3,
+	TP_ACPI_MULTI_MODE_STAND	= 1 << 4,
+	TP_ACPI_MULTI_MODE_TENT		= 1 << 5,
+	TP_ACPI_MULTI_MODE_STAND_TENT	= 1 << 6,
+};
+
+enum {
+	/* The following modes are considered tablet mode for the purpose of
+	 * reporting the status to userspace. i.e. in all these modes it makes
+	 * sense to disable the laptop input devices such as touchpad and
+	 * keyboard.
+	 */
+	TP_ACPI_MULTI_MODE_TABLET_LIKE	= TP_ACPI_MULTI_MODE_TABLET |
+					  TP_ACPI_MULTI_MODE_STAND |
+					  TP_ACPI_MULTI_MODE_TENT |
+					  TP_ACPI_MULTI_MODE_STAND_TENT,
+};
 
 static int hotkey_get_wlsw(void)
 {
@@ -2066,6 +2085,90 @@ static int hotkey_get_wlsw(void)
 	return (status) ? TPACPI_RFK_RADIO_ON : TPACPI_RFK_RADIO_OFF;
 }
 
+static int hotkey_gmms_get_tablet_mode(int s, int *has_tablet_mode)
+{
+	int type = (s >> 16) & 0xffff;
+	int value = s & 0xffff;
+	int mode = TP_ACPI_MULTI_MODE_INVALID;
+	int valid_modes = 0;
+
+	if (has_tablet_mode)
+		*has_tablet_mode = 0;
+
+	switch (type) {
+	case 1:
+		valid_modes = TP_ACPI_MULTI_MODE_LAPTOP |
+			      TP_ACPI_MULTI_MODE_TABLET |
+			      TP_ACPI_MULTI_MODE_STAND_TENT;
+		break;
+	case 2:
+		valid_modes = TP_ACPI_MULTI_MODE_LAPTOP |
+			      TP_ACPI_MULTI_MODE_FLAT |
+			      TP_ACPI_MULTI_MODE_TABLET |
+			      TP_ACPI_MULTI_MODE_STAND |
+			      TP_ACPI_MULTI_MODE_TENT;
+		break;
+	case 3:
+		valid_modes = TP_ACPI_MULTI_MODE_LAPTOP |
+			      TP_ACPI_MULTI_MODE_FLAT;
+		break;
+	case 4:
+		valid_modes = TP_ACPI_MULTI_MODE_LAPTOP |
+			      TP_ACPI_MULTI_MODE_TABLET |
+			      TP_ACPI_MULTI_MODE_STAND |
+			      TP_ACPI_MULTI_MODE_TENT;
+		break;
+	case 5:
+		valid_modes = TP_ACPI_MULTI_MODE_LAPTOP |
+			      TP_ACPI_MULTI_MODE_FLAT |
+			      TP_ACPI_MULTI_MODE_TABLET |
+			      TP_ACPI_MULTI_MODE_STAND |
+			      TP_ACPI_MULTI_MODE_TENT;
+		break;
+	default:
+		pr_err("Unknown multi mode status type %d with value 0x%04X, please report this to %s\n",
+		       type, value, TPACPI_MAIL);
+		return 0;
+	}
+
+	if (has_tablet_mode && (valid_modes & TP_ACPI_MULTI_MODE_TABLET_LIKE))
+		*has_tablet_mode = 1;
+
+	switch (value) {
+	case 1:
+		mode = TP_ACPI_MULTI_MODE_LAPTOP;
+		break;
+	case 2:
+		mode = TP_ACPI_MULTI_MODE_FLAT;
+		break;
+	case 3:
+		mode = TP_ACPI_MULTI_MODE_TABLET;
+		break;
+	case 4:
+		if (type == 1)
+			mode = TP_ACPI_MULTI_MODE_STAND_TENT;
+		else
+			mode = TP_ACPI_MULTI_MODE_STAND;
+		break;
+	case 5:
+		mode = TP_ACPI_MULTI_MODE_TENT;
+		break;
+	default:
+		if (type == 5 && value == 0xffff) {
+			pr_warn("Multi mode status is undetected, assuming laptop\n");
+			return 0;
+		}
+	}
+
+	if (!(mode & valid_modes)) {
+		pr_err("Unknown/reserved multi mode value 0x%04X for type %d, please report this to %s\n",
+		       value, type, TPACPI_MAIL);
+		return 0;
+	}
+
+	return !!(mode & TP_ACPI_MULTI_MODE_TABLET_LIKE);
+}
+
 static int hotkey_get_tablet_mode(int *status)
 {
 	int s;
@@ -2077,11 +2180,11 @@ static int hotkey_get_tablet_mode(int *status)
 
 		*status = ((s & TP_HOTKEY_TABLET_MASK) != 0);
 		break;
-	case TP_HOTKEY_TABLET_USES_CMMD:
-		if (!acpi_evalf(ec_handle, &s, "CMMD", "d"))
+	case TP_HOTKEY_TABLET_USES_GMMS:
+		if (!acpi_evalf(hkey_handle, &s, "GMMS", "dd", 0))
 			return -EIO;
 
-		*status = (s == TP_EC_CMMD_TABLET_MODE);
+		*status = hotkey_gmms_get_tablet_mode(s, NULL);
 		break;
 	default:
 		break;
@@ -3113,16 +3216,19 @@ static int hotkey_init_tablet_mode(void)
 	int in_tablet_mode = 0, res;
 	char *type = NULL;
 
-	if (acpi_evalf(hkey_handle, &res, "MHKG", "qd")) {
+	if (acpi_evalf(hkey_handle, &res, "GMMS", "qdd", 0)) {
+		int has_tablet_mode;
+
+		in_tablet_mode = hotkey_gmms_get_tablet_mode(res,
+							     &has_tablet_mode);
+		if (has_tablet_mode)
+			tp_features.hotkey_tablet = TP_HOTKEY_TABLET_USES_GMMS;
+		type = "GMMS";
+	} else if (acpi_evalf(hkey_handle, &res, "MHKG", "qd")) {
 		/* For X41t, X60t, X61t Tablets... */
 		tp_features.hotkey_tablet = TP_HOTKEY_TABLET_USES_MHKG;
 		in_tablet_mode = !!(res & TP_HOTKEY_TABLET_MASK);
 		type = "MHKG";
-	} else if (acpi_evalf(ec_handle, &res, "CMMD", "qd")) {
-		/* For X1 Yoga (2016) */
-		tp_features.hotkey_tablet = TP_HOTKEY_TABLET_USES_CMMD;
-		in_tablet_mode = res == TP_EC_CMMD_TABLET_MODE;
-		type = "CMMD";
 	}
 
 	if (!tp_features.hotkey_tablet)