platform/x86: toshiba_acpi: Add fan RPM reading (internals)

This add the internal feature detection and reading function for fan RPM.

The approach is based on tracing ACPI calls using AMLI (a tracer/debugger
built into ACPI.sys) while using the Windows cooling self-test software.

The call used is {HCI_GET, 0x45, 0, 1, 0, 0} which returns:
{0x0, 0x45, fan_rpm, probably_max_rpm, 0x0, 0x0}

What is probably the max RPM is not currently used.
Signed-off-by: Arvid Norlander <lkml@vorpal.se>
Link: https://lore.kernel.org/r/20220902174018.1720029-2-lkml@vorpal.seReviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/toshiba_acpi.c

@@ -106,6 +106,7 @@ MODULE_LICENSE("GPL");
 #define HCI_VIDEO_OUT			0x001c
 #define HCI_HOTKEY_EVENT		0x001e
 #define HCI_LCD_BRIGHTNESS		0x002a
+#define HCI_FAN_RPM			0x0045
 #define HCI_WIRELESS			0x0056
 #define HCI_ACCELEROMETER		0x006d
 #define HCI_COOLING_METHOD		0x007f
@@ -185,6 +186,7 @@ struct toshiba_acpi_dev {
 	unsigned int illumination_supported:1;
 	unsigned int video_supported:1;
 	unsigned int fan_supported:1;
+	unsigned int fan_rpm_supported:1;
 	unsigned int system_event_supported:1;
 	unsigned int ntfy_supported:1;
 	unsigned int info_supported:1;
@@ -1611,6 +1613,29 @@ static const struct proc_ops fan_proc_ops = {
 	.proc_write	= fan_proc_write,
 };
 
+/* Fan RPM */
+static int get_fan_rpm(struct toshiba_acpi_dev *dev, u32 *rpm)
+{
+	u32 in[TCI_WORDS] = { HCI_GET, HCI_FAN_RPM, 0, 1, 0, 0 };
+	u32 out[TCI_WORDS];
+	acpi_status status = tci_raw(dev, in, out);
+
+	if (ACPI_FAILURE(status)) {
+		pr_err("ACPI call to get Fan speed failed\n");
+		return -EIO;
+	}
+
+	if (out[0] == TOS_NOT_SUPPORTED)
+		return -ENODEV;
+
+	if (out[0] == TOS_SUCCESS) {
+		*rpm = out[2];
+		return 0;
+	}
+
+	return -EIO;
+}
+
 static int keys_proc_show(struct seq_file *m, void *v)
 {
 	struct toshiba_acpi_dev *dev = m->private;
@@ -2915,6 +2940,8 @@ static void print_supported_features(struct toshiba_acpi_dev *dev)
 		pr_cont(" video-out");
 	if (dev->fan_supported)
 		pr_cont(" fan");
+	if (dev->fan_rpm_supported)
+		pr_cont(" fan-rpm");
 	if (dev->tr_backlight_supported)
 		pr_cont(" transflective-backlight");
 	if (dev->illumination_supported)
@@ -3144,6 +3171,9 @@ static int toshiba_acpi_add(struct acpi_device *acpi_dev)
 	ret = get_fan_status(dev, &dummy);
 	dev->fan_supported = !ret;
 
+	ret = get_fan_rpm(dev, &dummy);
+	dev->fan_rpm_supported = !ret;
+
 	toshiba_wwan_available(dev);
 	if (dev->wwan_supported)
 		toshiba_acpi_setup_wwan_rfkill(dev);