sfp: add high power module support

This patch is the result of work by both Jon Nettleton and Russell King.
Jon wrote the original patch, adding support for SFP modules which
require a power level greater than '1'.

Russell's changes:
- Fix the power levels for big-endian, and make the code flow better.
- Convert to use device_property_read_u8()
- Warn for power levels exceeding host level
  SFF-8431 says:

  "To avoid exceeding system power supply limits and cooling capacity,
   all modules at power up by default shall operate with up to 1.0 W.
   Hosts supporting Power Level II or III operation may enable a Power
   Level II or III module through the 2-wire interface. Power Level II
   or III modules shall assert the power level declaration bit of
   SFF-8472."

  Print a warning for modules that exceed the host power level, and
  leave them operating in power level 1.

- Fix i2c write
  The first byte of any write after the bus address is always the
  device address.  In order to write a value to device D, address I,
  value V, we need to generate on the bus:

    S DDDDDDDD A IIIIIIII A VVVVVVVV A P

  where S = start, R = restart, A = ack, P = stop.  Splitting this
  as two:

    S DDDDDDDD A IIIIIIII A R DDDDDDDD A VVVVVVVV A P

  results in the device's address register being written first by I
  and then by V - the addressed register within the device is not
  written.

- Avoid power mode switching if 0xa2 is not implemented
  Some modules indicate that they support power level II or power level
  III, but do not implement address 0xa2, meaning that the bit to set
  them to high power mode is not accessible.

  These modules appear to have the sff8472_compliance field set to zero,
  and also do not implement diagnostics.  Detect this, but also ensure
  that the module does not require the address switching mode, which we
  do not implement.

- Use mW for power level rather than power level number.

- Fix high power mode transition
  We must not switch to SFP_MOD_PRESENT state until we have finished
  initialising, because the remaining state machines check for that
  state.  Add SFP_MOD_HPOWER as an intermediate state.

- Use definition for I2C register address rather than constant.

Signed-off-by: Jon Nettleton <jon@solid-run.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/sfp.c

@@ -42,6 +42,7 @@ enum {
 
 	SFP_MOD_EMPTY = 0,
 	SFP_MOD_PROBE,
+	SFP_MOD_HPOWER,
 	SFP_MOD_PRESENT,
 	SFP_MOD_ERROR,
 
@@ -86,6 +87,7 @@ static const enum gpiod_flags gpio_flags[] = {
  * access the I2C EEPROM.  However, Avago modules require 300ms.
  */
 #define T_PROBE_INIT	msecs_to_jiffies(300)
+#define T_HPOWER_LEVEL	msecs_to_jiffies(300)
 #define T_PROBE_RETRY	msecs_to_jiffies(100)
 
 /* SFP modules appear to always have their PHY configured for bus address
@@ -110,10 +112,12 @@ struct sfp {
 	struct sfp_bus *sfp_bus;
 	struct phy_device *mod_phy;
 	const struct sff_data *type;
+	u32 max_power_mW;
 
 	unsigned int (*get_state)(struct sfp *);
 	void (*set_state)(struct sfp *, unsigned int);
 	int (*read)(struct sfp *, bool, u8, void *, size_t);
+	int (*write)(struct sfp *, bool, u8, void *, size_t);
 
 	struct gpio_desc *gpio[GPIO_MAX];
 
@@ -201,10 +205,11 @@ static void sfp_gpio_set_state(struct sfp *sfp, unsigned int state)
 	}
 }
 
-static int sfp__i2c_read(struct i2c_adapter *i2c, u8 bus_addr, u8 dev_addr,
-			 void *buf, size_t len)
+static int sfp_i2c_read(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
+			size_t len)
 {
 	struct i2c_msg msgs[2];
+	u8 bus_addr = a2 ? 0x51 : 0x50;
 	int ret;
 
 	msgs[0].addr = bus_addr;
@@ -216,17 +221,38 @@ static int sfp__i2c_read(struct i2c_adapter *i2c, u8 bus_addr, u8 dev_addr,
 	msgs[1].len = len;
 	msgs[1].buf = buf;
 
-	ret = i2c_transfer(i2c, msgs, ARRAY_SIZE(msgs));
+	ret = i2c_transfer(sfp->i2c, msgs, ARRAY_SIZE(msgs));
 	if (ret < 0)
 		return ret;
 
 	return ret == ARRAY_SIZE(msgs) ? len : 0;
 }
 
-static int sfp_i2c_read(struct sfp *sfp, bool a2, u8 addr, void *buf,
-			size_t len)
+static int sfp_i2c_write(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
+	size_t len)
 {
-	return sfp__i2c_read(sfp->i2c, a2 ? 0x51 : 0x50, addr, buf, len);
+	struct i2c_msg msgs[1];
+	u8 bus_addr = a2 ? 0x51 : 0x50;
+	int ret;
+
+	msgs[0].addr = bus_addr;
+	msgs[0].flags = 0;
+	msgs[0].len = 1 + len;
+	msgs[0].buf = kmalloc(1 + len, GFP_KERNEL);
+	if (!msgs[0].buf)
+		return -ENOMEM;
+
+	msgs[0].buf[0] = dev_addr;
+	memcpy(&msgs[0].buf[1], buf, len);
+
+	ret = i2c_transfer(sfp->i2c, msgs, ARRAY_SIZE(msgs));
+
+	kfree(msgs[0].buf);
+
+	if (ret < 0)
+		return ret;
+
+	return ret == ARRAY_SIZE(msgs) ? len : 0;
 }
 
 static int sfp_i2c_configure(struct sfp *sfp, struct i2c_adapter *i2c)
@@ -239,6 +265,7 @@ static int sfp_i2c_configure(struct sfp *sfp, struct i2c_adapter *i2c)
 
 	sfp->i2c = i2c;
 	sfp->read = sfp_i2c_read;
+	sfp->write = sfp_i2c_write;
 
 	i2c_mii = mdio_i2c_alloc(sfp->dev, i2c);
 	if (IS_ERR(i2c_mii))
@@ -274,6 +301,11 @@ static int sfp_read(struct sfp *sfp, bool a2, u8 addr, void *buf, size_t len)
 	return sfp->read(sfp, a2, addr, buf, len);
 }
 
+static int sfp_write(struct sfp *sfp, bool a2, u8 addr, void *buf, size_t len)
+{
+	return sfp->write(sfp, a2, addr, buf, len);
+}
+
 static unsigned int sfp_check(void *buf, size_t len)
 {
 	u8 *p, check;
@@ -462,21 +494,83 @@ static void sfp_sm_mod_init(struct sfp *sfp)
 		sfp_sm_probe_phy(sfp);
 }
 
+static int sfp_sm_mod_hpower(struct sfp *sfp)
+{
+	u32 power;
+	u8 val;
+	int err;
+
+	power = 1000;
+	if (sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_POWER_DECL))
+		power = 1500;
+	if (sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_HIGH_POWER_LEVEL))
+		power = 2000;
+
+	if (sfp->id.ext.sff8472_compliance == SFP_SFF8472_COMPLIANCE_NONE &&
+	    (sfp->id.ext.diagmon & (SFP_DIAGMON_DDM | SFP_DIAGMON_ADDRMODE)) !=
+	    SFP_DIAGMON_DDM) {
+		/* The module appears not to implement bus address 0xa2,
+		 * or requires an address change sequence, so assume that
+		 * the module powers up in the indicated power mode.
+		 */
+		if (power > sfp->max_power_mW) {
+			dev_err(sfp->dev,
+				"Host does not support %u.%uW modules\n",
+				power / 1000, (power / 100) % 10);
+			return -EINVAL;
+		}
+		return 0;
+	}
+
+	if (power > sfp->max_power_mW) {
+		dev_warn(sfp->dev,
+			 "Host does not support %u.%uW modules, module left in power mode 1\n",
+			 power / 1000, (power / 100) % 10);
+		return 0;
+	}
+
+	if (power <= 1000)
+		return 0;
+
+	err = sfp_read(sfp, true, SFP_EXT_STATUS, &val, sizeof(val));
+	if (err != sizeof(val)) {
+		dev_err(sfp->dev, "Failed to read EEPROM: %d\n", err);
+		err = -EAGAIN;
+		goto err;
+	}
+
+	val |= BIT(0);
+
+	err = sfp_write(sfp, true, SFP_EXT_STATUS, &val, sizeof(val));
+	if (err != sizeof(val)) {
+		dev_err(sfp->dev, "Failed to write EEPROM: %d\n", err);
+		err = -EAGAIN;
+		goto err;
+	}
+
+	dev_info(sfp->dev, "Module switched to %u.%uW power level\n",
+		 power / 1000, (power / 100) % 10);
+	return T_HPOWER_LEVEL;
+
+err:
+	return err;
+}
+
 static int sfp_sm_mod_probe(struct sfp *sfp)
 {
 	/* SFP module inserted - read I2C data */
 	struct sfp_eeprom_id id;
 	u8 check;
-	int err;
+	int ret;
 
-	err = sfp_read(sfp, false, 0, &id, sizeof(id));
-	if (err < 0) {
-		dev_err(sfp->dev, "failed to read EEPROM: %d\n", err);
+	ret = sfp_read(sfp, false, 0, &id, sizeof(id));
+	if (ret < 0) {
+		dev_err(sfp->dev, "failed to read EEPROM: %d\n", ret);
 		return -EAGAIN;
 	}
 
-	if (err != sizeof(id)) {
-		dev_err(sfp->dev, "EEPROM short read: %d\n", err);
+	if (ret != sizeof(id)) {
+		dev_err(sfp->dev, "EEPROM short read: %d\n", ret);
 		return -EAGAIN;
 	}
 
@@ -521,7 +615,11 @@ static int sfp_sm_mod_probe(struct sfp *sfp)
 		dev_warn(sfp->dev,
 			 "module address swap to access page 0xA2 is not supported.\n");
 
-	return sfp_module_insert(sfp->sfp_bus, &sfp->id);
+	ret = sfp_module_insert(sfp->sfp_bus, &sfp->id);
+	if (ret < 0)
+		return ret;
+
+	return sfp_sm_mod_hpower(sfp);
 }
 
 static void sfp_sm_mod_remove(struct sfp *sfp)
@@ -560,17 +658,25 @@ static void sfp_sm_event(struct sfp *sfp, unsigned int event)
 		if (event == SFP_E_REMOVE) {
 			sfp_sm_ins_next(sfp, SFP_MOD_EMPTY, 0);
 		} else if (event == SFP_E_TIMEOUT) {
-			int err = sfp_sm_mod_probe(sfp);
+			int val = sfp_sm_mod_probe(sfp);
 
-			if (err == 0)
+			if (val == 0)
 				sfp_sm_ins_next(sfp, SFP_MOD_PRESENT, 0);
-			else if (err == -EAGAIN)
-				sfp_sm_set_timer(sfp, T_PROBE_RETRY);
-			else
+			else if (val > 0)
+				sfp_sm_ins_next(sfp, SFP_MOD_HPOWER, val);
+			else if (val != -EAGAIN)
 				sfp_sm_ins_next(sfp, SFP_MOD_ERROR, 0);
+			else
+				sfp_sm_set_timer(sfp, T_PROBE_RETRY);
 		}
 		break;
 
+	case SFP_MOD_HPOWER:
+		if (event == SFP_E_TIMEOUT) {
+			sfp_sm_ins_next(sfp, SFP_MOD_PRESENT, 0);
+			break;
+		}
+		/* fallthrough */
 	case SFP_MOD_PRESENT:
 	case SFP_MOD_ERROR:
 		if (event == SFP_E_REMOVE) {
@@ -889,6 +995,14 @@ static int sfp_probe(struct platform_device *pdev)
 	if (!(sfp->gpio[GPIO_MODDEF0]))
 		sfp->get_state = sff_gpio_get_state;
 
+	device_property_read_u32(&pdev->dev, "maximum-power-milliwatt",
+				 &sfp->max_power_mW);
+	if (!sfp->max_power_mW)
+		sfp->max_power_mW = 1000;
+
+	dev_info(sfp->dev, "Host maximum power %u.%uW\n",
+		 sfp->max_power_mW / 1000, (sfp->max_power_mW / 100) % 10);
+
 	sfp->sfp_bus = sfp_register_socket(sfp->dev, sfp, &sfp_module_ops);
 	if (!sfp->sfp_bus)
 		return -ENOMEM;