applesmc-t2: fan support on T2 Macs

T2 Macs changed the fan values from shorts to
floats, and changed the fan manual override
setting from a bitmask to a per-fan boolean
named F0Md (thanks to @kleuter for mentioning
it).

A minimal soft-float implementation has been
written for convert floats to integers (and vice
versa).

Signed-off-by: Aun-Ali Zaidi <admin@kodeit.net>

Author: Paul Pawlowski

drivers/hwmon/applesmc-t2.c

@@ -87,6 +87,7 @@
 #define FAN_ID_FMT		"F%dID" /* r-o char[16] */
 
 #define TEMP_SENSOR_TYPE	"sp78"
+#define FLOAT_TYPE		"flt "
 
 /* List of keys used to read/write fan speeds */
 static const char *const fan_speed_fmt[] = {
@@ -96,6 +97,7 @@ static const char *const fan_speed_fmt[] = {
 	"F%dSf",		/* safe speed - not all models */
 	"F%dTg",		/* target speed (manual: rw) */
 };
+#define FAN_MANUAL_FMT "F%dMd"
 
 #define INIT_TIMEOUT_MSECS	5000	/* wait up to 5s for device init ... */
 #define INIT_WAIT_MSECS		50	/* ... in 50ms increments */
@@ -734,6 +736,42 @@ static int applesmc_read_s16(struct applesmc_device *smc,
 	return 0;
 }
 
+/**
+ * applesmc_float_to_u32 - Retrieve the integral part of a float.
+ * This is needed because Apple made fans use float values in the T2.
+ * The fractional point is not significantly useful though, and the integral
+ * part can be easily extracted.
+ */
+static inline u32 applesmc_float_to_u32(u32 d)
+{
+	u8 sign = (u8) ((d >> 31) & 1);
+	s32 exp = (s32) ((d >> 23) & 0xff) - 0x7f;
+	u32 fr = d & ((1u << 23) - 1);
+
+	if (sign || exp < 0)
+		return 0;
+
+	return (u32) ((1u << exp) + (fr >> (23 - exp)));
+}
+
+/**
+ * applesmc_u32_to_float - Convert an u32 into a float.
+ * See applesmc_float_to_u32 for a rationale.
+ */
+static inline u32 applesmc_u32_to_float(u32 d)
+{
+	u32 dc = d, bc = 0, exp;
+
+	if (!d)
+		return 0;
+
+	while (dc >>= 1)
+		++bc;
+	exp = 0x7f + bc;
+
+	return (u32) ((exp << 23) |
+		((d << (23 - (exp - 0x7f))) & ((1u << 23) - 1)));
+}
 /*
  * applesmc_device_init - initialize the accelerometer.  Can sleep.
  */
@@ -1241,6 +1279,7 @@ static ssize_t applesmc_show_fan_speed(struct device *dev,
 				struct device_attribute *attr, char *sysfsbuf)
 {
 	struct applesmc_device *smc = dev_get_drvdata(dev);
+	const struct applesmc_entry *entry;
 	int ret;
 	unsigned int speed = 0;
 	char newkey[5];
@@ -1249,11 +1288,21 @@ static ssize_t applesmc_show_fan_speed(struct device *dev,
 	scnprintf(newkey, sizeof(newkey), fan_speed_fmt[to_option(attr)],
 		  to_index(attr));
 
-	ret = applesmc_read_key(smc, newkey, buffer, 2);
+	entry = applesmc_get_entry_by_key(smc, newkey);
+	if (IS_ERR(entry))
+		return PTR_ERR(entry);
+
+	if (!strcmp(entry->type, FLOAT_TYPE)) {
+		ret = applesmc_read_entry(smc, entry, (u8 *) &speed, 4);
+		speed = applesmc_float_to_u32(speed);
+	} else {
+		ret = applesmc_read_entry(smc, entry, buffer, 2);
+		speed = ((buffer[0] << 8 | buffer[1]) >> 2);
+	}
+
 	if (ret)
 		return ret;
 
-	speed = ((buffer[0] << 8 | buffer[1]) >> 2);
 	return sysfs_emit(sysfsbuf, "%u\n", speed);
 }
 
@@ -1262,6 +1311,7 @@ static ssize_t applesmc_store_fan_speed(struct device *dev,
 					const char *sysfsbuf, size_t count)
 {
 	struct applesmc_device *smc = dev_get_drvdata(dev);
+	const struct applesmc_entry *entry;
 	int ret;
 	unsigned long speed;
 	char newkey[5];
@@ -1273,9 +1323,18 @@ static ssize_t applesmc_store_fan_speed(struct device *dev,
 	scnprintf(newkey, sizeof(newkey), fan_speed_fmt[to_option(attr)],
 		  to_index(attr));
 
-	buffer[0] = (speed >> 6) & 0xff;
-	buffer[1] = (speed << 2) & 0xff;
-	ret = applesmc_write_key(smc, newkey, buffer, 2);
+	entry = applesmc_get_entry_by_key(smc, newkey);
+	if (IS_ERR(entry))
+		return PTR_ERR(entry);
+
+	if (!strcmp(entry->type, FLOAT_TYPE)) {
+		speed = applesmc_u32_to_float(speed);
+		ret = applesmc_write_entry(smc, entry, (u8 *) &speed, 4);
+	} else {
+		buffer[0] = (speed >> 6) & 0xff;
+		buffer[1] = (speed << 2) & 0xff;
+		ret = applesmc_write_key(smc, newkey, buffer, 2);
+	}
 
 	if (ret)
 		return ret;
@@ -1290,12 +1349,26 @@ static ssize_t applesmc_show_fan_manual(struct device *dev,
 	int ret;
 	u16 manual = 0;
 	u8 buffer[2];
+	char newkey[5];
+	bool has_newkey = false;
+
+	scnprintf(newkey, sizeof(newkey), FAN_MANUAL_FMT, to_index(attr));
+
+	ret = applesmc_has_key(smc, newkey, &has_newkey);
+	if (ret)
+		return ret;
+
+	if (has_newkey) {
+		ret = applesmc_read_key(smc, newkey, buffer, 1);
+		manual = buffer[0];
+	} else {
+		ret = applesmc_read_key(smc, FANS_MANUAL, buffer, 2);
+		manual = ((buffer[0] << 8 | buffer[1]) >> to_index(attr)) & 0x01;
+	}
 
-	ret = applesmc_read_key(smc, FANS_MANUAL, buffer, 2);
 	if (ret)
 		return ret;
 
-	manual = ((buffer[0] << 8 | buffer[1]) >> to_index(attr)) & 0x01;
 	return sysfs_emit(sysfsbuf, "%d\n", manual);
 }
 
@@ -1306,27 +1379,39 @@ static ssize_t applesmc_store_fan_manual(struct device *dev,
 	struct applesmc_device *smc = dev_get_drvdata(dev);
 	int ret;
 	u8 buffer[2];
+	char newkey[5];
+	bool has_newkey = false;
 	unsigned long input;
 	u16 val;
 
 	if (kstrtoul(sysfsbuf, 10, &input) < 0)
 		return -EINVAL;
 
-	ret = applesmc_read_key(smc, FANS_MANUAL, buffer, 2);
+	scnprintf(newkey, sizeof(newkey), FAN_MANUAL_FMT, to_index(attr));
+
+	ret = applesmc_has_key(smc, newkey, &has_newkey);
 	if (ret)
-		goto out;
+		return ret;
 
-	val = (buffer[0] << 8 | buffer[1]);
+	if (has_newkey) {
+		buffer[0] = input & 1;
+		ret = applesmc_write_key(smc, newkey, buffer, 1);
+	} else {
+		ret = applesmc_read_key(smc, FANS_MANUAL, buffer, 2);
+		val = (buffer[0] << 8 | buffer[1]);
+		if (ret)
+			goto out;
 
-	if (input)
-		val = val | (0x01 << to_index(attr));
-	else
-		val = val & ~(0x01 << to_index(attr));
+		if (input)
+			val = val | (0x01 << to_index(attr));
+		else
+			val = val & ~(0x01 << to_index(attr));
 
-	buffer[0] = (val >> 8) & 0xFF;
-	buffer[1] = val & 0xFF;
+		buffer[0] = (val >> 8) & 0xFF;
+		buffer[1] = val & 0xFF;
 
-	ret = applesmc_write_key(smc, FANS_MANUAL, buffer, 2);
+		ret = applesmc_write_key(smc, FANS_MANUAL, buffer, 2);
+	}
 
 out:
 	if (ret)