[RESEND PATCH 3/5] platform/x86: bitland-mifs-wmi: read fan tach from EC window on MIFS v2

[孙 誉铭]

The MIFS v2 firmware implements no WMI function for fan speeds (nor
for the CPU thermometer), so on these machines the hwmon device
reported zero RPM on every channel.

The fan tachometers instead live in the EC shared-memory window at
0xFE0B0300 (DSDT \_SB.PC00.LPCB.Q_EC region "ERAM") as little-endian
u16 RPM values at offsets 0x69 and 0x6B (0 = fan stopped). Map the
window on v2 systems and expose the two fans with proper labels; hide
the non-existent third fan and temperature channels.

Offsets verified by diffing the window between idle and sustained load
(tach values ramp 0 -> ~2700 RPM and back) on a Xiaomi Book Pro 14.

Signed-off-by: Yuming Sun <wolf109909@xxxxxxxxxxx>
---
 drivers/platform/x86/bitland-mifs-wmi.c | 68 +++++++++++++++++++++++--
 1 file changed, 65 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/x86/bitland-mifs-wmi.c b/drivers/platform/x86/bitland-mifs-wmi.c
index 342dd7e1..5f7c85a8 100644
--- a/drivers/platform/x86/bitland-mifs-wmi.c
+++ b/drivers/platform/x86/bitland-mifs-wmi.c
@@ -17,6 +17,7 @@
 #include <linux/err.h>
 #include <linux/hwmon.h>
 #include <linux/init.h>
+#include <linux/io.h>
 #include <linux/input-event-codes.h>
 #include <linux/input.h>
 #include <linux/input/sparse-keymap.h>
@@ -151,6 +152,16 @@ struct bitland_mifs_output {
  */
 #define MIFS_STATUS_ERROR	0xe000
 
+/*
+ * MIFS v2 EC shared-memory window (DSDT \_SB.PC00.LPCB.Q_EC region
+ * "ERAM"). The firmware exposes no WMI fan function, but the fan
+ * tachometers live here as little-endian u16 RPM (0 = fan stopped).
+ */
+#define MIFS_V2_EC_MEM_BASE	0xFE0B0300
+#define MIFS_V2_EC_MEM_SIZE	0x100
+#define MIFS_V2_EC_REG_FAN1	0x69
+#define MIFS_V2_EC_REG_FAN2	0x6B
+
 static u16 mifs_status(const struct bitland_mifs_output *out)
 {
 	return out->reserved1 | (out->operation << 8);
@@ -188,6 +199,7 @@ struct bitland_mifs_wmi_data {
 	enum platform_profile_option saved_profile;
 	bool profile_valid;
 	bool is_v2;	/* MIFS v2 firmware: QFAN perf-mode codes */
+	u8 __iomem *ec_mem;	/* v2 EC shared-memory window */
 };
 
 static int bitland_mifs_wmi_call(struct bitland_mifs_wmi_data *data,
@@ -421,6 +433,27 @@ static const char *const fan_labels[] = {
 	"SYS", /* 2 */
 };
 
+static const char *const fan_labels_v2[] = {
+	"Left Fan", /* 0 */
+	"Right Fan", /* 1 */
+};
+
+static umode_t laptop_hwmon_visible(const void *drvdata,
+				    enum hwmon_sensor_types type,
+				    u32 attr, int channel)
+{
+	const struct bitland_mifs_wmi_data *data = drvdata;
+
+	/* v2 firmware: two fans, no CPU temperature channel */
+	if (data->is_v2) {
+		if (type == hwmon_fan && channel < 2)
+			return 0444;
+		return 0;
+	}
+
+	return 0444;
+}
+
 static int laptop_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
 			     u32 attr, int channel, long *val)
 {
@@ -433,6 +466,22 @@ static int laptop_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
 	struct bitland_mifs_output res;
 	int ret;
 
+	/* v2: tachometers are u16 RPM in the EC shared-memory window */
+	if (data->is_v2) {
+		if (type != hwmon_fan || !data->ec_mem)
+			return -EINVAL;
+		switch (channel) {
+		case 0:
+			*val = get_unaligned_le16(data->ec_mem + MIFS_V2_EC_REG_FAN1);
+			return 0;
+		case 1:
+			*val = get_unaligned_le16(data->ec_mem + MIFS_V2_EC_REG_FAN2);
+			return 0;
+		default:
+			return -EINVAL;
+		}
+	}
+
 	switch (type) {
 	case hwmon_temp:
 		input.function = WMI_FN_CPU_THERMOMETER;
@@ -468,9 +517,13 @@ static int laptop_hwmon_read_string(struct device *dev,
 				    enum hwmon_sensor_types type, u32 attr,
 				    int channel, const char **str)
 {
+	struct bitland_mifs_wmi_data *data = dev_get_drvdata(dev);
+	const char *const *labels = data->is_v2 ? fan_labels_v2 : fan_labels;
+	int nlabels = data->is_v2 ? ARRAY_SIZE(fan_labels_v2) : ARRAY_SIZE(fan_labels);
+
 	if (type == hwmon_fan && attr == hwmon_fan_label) {
-		if (channel >= 0 && channel < ARRAY_SIZE(fan_labels)) {
-			*str = fan_labels[channel];
+		if (channel >= 0 && channel < nlabels) {
+			*str = labels[channel];
 			return 0;
 		}
 	}
@@ -486,7 +539,7 @@ static const struct hwmon_channel_info *laptop_hwmon_info[] = {
 };
 
 static const struct hwmon_ops laptop_hwmon_ops = {
-	.visible = 0444,
+	.is_visible = laptop_hwmon_visible,
 	.read = laptop_hwmon_read,
 	.read_string = laptop_hwmon_read_string,
 };
@@ -782,6 +835,15 @@ static int bitland_mifs_wmi_probe(struct wmi_device *wdev, const void *context)
 			dev_info(&wdev->dev,
 				 "MIFS v2 firmware detected (QFAN mode codes)\n");
 		}
+
+		if (drv_data->is_v2) {
+			drv_data->ec_mem = devm_ioremap(&wdev->dev,
+							MIFS_V2_EC_MEM_BASE,
+							MIFS_V2_EC_MEM_SIZE);
+			if (!drv_data->ec_mem)
+				dev_warn(&wdev->dev,
+					 "cannot map EC window, fan tach unavailable\n");
+		}
 	}
 
 	if (dev_type == BITLAND_WMI_EVENT) {
-- 
2.55.0