[PATCH net 2/2] net: usb: aqc111: Support for thermal throttling feature

[Igor Russkikh <Igor.Russkikh@aquantia.com>]

From: Dmitry Bezrukov <dmitry.bezrukov@aquantia.com>

Lab testing shows that chip may get overheated when
network link is connected on high speed (2.5G/5G).

Default hardware design uses only passive heatsink without a cooler,
and that makes things worse.

To prevent possible chip damage here we add throttling mechanism.

There is a worker that monitors the PHY's temperature via reading
PHY registers. When PHY's temperature reaches the critical threshold
(it is 106 degrees of Celsius) it changes the link speed to the lowest
regardless user/default link speed settings. It should reduce the PHY's
temperature to normal numbers.

When the PHY's temparature is back to normal (low threshold, it is
85 degrees) it restores user/default link speed settings.

Signed-off-by: Dmitry Bezrukov <dmitry.bezrukov@aquantia.com>
Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
---
 drivers/net/usb/aqc111.c | 78 ++++++++++++++++++++++++++++++++++++++++
 drivers/net/usb/aqc111.h |  8 +++++
 2 files changed, 86 insertions(+)

diff --git a/drivers/net/usb/aqc111.c b/drivers/net/usb/aqc111.c
index 8867f6a3eaa7..fa6b9dfc2a6f 100644
--- a/drivers/net/usb/aqc111.c
+++ b/drivers/net/usb/aqc111.c
@@ -17,6 +17,7 @@
 #include <linux/usb/cdc.h>
 #include <linux/usb/usbnet.h>
 #include <linux/linkmode.h>
+#include <linux/workqueue.h>
 
 #include "aqc111.h"
 
@@ -334,6 +335,9 @@ static void aqc111_set_phy_speed(struct usbnet *dev, u8 autoneg, u16 speed)
 	aqc111_data->phy_cfg |= (3 << AQ_DSH_RETRIES_SHIFT) &
 				AQ_DSH_RETRIES_MASK;
 
+	if (aqc111_data->thermal_throttling)
+		speed = SPEED_100;
+
 	if (autoneg == AUTONEG_ENABLE) {
 		switch (speed) {
 		case SPEED_5000:
@@ -714,6 +718,8 @@ static int aqc111_bind(struct usbnet *dev, struct usb_interface *intf)
 	/* store aqc111_data pointer in device data field */
 	dev->driver_priv = aqc111_data;
 
+	aqc111_data->dev = dev;
+
 	/* Init the MAC address */
 	ret = aqc111_read_perm_mac(dev);
 	if (ret)
@@ -991,6 +997,71 @@ static int aqc111_link_reset(struct usbnet *dev)
 	return 0;
 }
 
+int aqc111_get_temperature(struct usbnet *dev, u32 *temperature)
+{
+	u16 reg16 = 0;
+
+	if (aqc111_mdio_read(dev, AQ_GLB_THERMAL_STATUS2, AQ_PHY_GLOBAL_ADDR,
+			     &reg16) < 0)
+		goto err;
+
+	if (!(reg16 & AQ_THERM_ST_READY))
+		goto err;
+
+	if (aqc111_mdio_read(dev, AQ_GLB_THERMAL_STATUS1, AQ_PHY_GLOBAL_ADDR,
+			     &reg16) < 0)
+		goto err;
+
+	/*convert from 1/256 to 1/100 degrees of Celsius*/
+	*temperature = (u32)reg16 * 100 / 256;
+	return 0;
+
+err:
+	*temperature = 0;
+	return -1;
+}
+
+void aqc111_thermal_work_cb(struct work_struct *w)
+{
+	struct delayed_work *dw = to_delayed_work(w);
+	struct aqc111_data *aqc111_data = container_of(dw, struct aqc111_data,
+						       therm_work);
+	unsigned long timeout = msecs_to_jiffies(AQ_THERMAL_TIMER_MS);
+	struct usbnet *dev = aqc111_data->dev;
+	u32 temperature = 0;
+	u8 reset_speed = 0;
+
+	if (!aqc111_data->link)
+		/* poll not so frequently */
+		timeout *= 2;
+
+	if (aqc111_get_temperature(dev, &temperature) != 0)
+		goto end;
+
+	if (aqc111_data->thermal_throttling &&
+	    temperature <= AQ_NORMAL_TEMP_THRESHOLD) {
+		netdev_info(dev->net, "The temperature is back to normal(%u)",
+			    AQ_NORMAL_TEMP_THRESHOLD / 100);
+		aqc111_data->thermal_throttling = 0;
+		reset_speed = 1;
+	}
+
+	if (!aqc111_data->thermal_throttling &&
+	    temperature >= AQ_CRITICAL_TEMP_THRESHOLD) {
+		netdev_warn(dev->net, "Critical temperature(%u) is reached",
+			    AQ_CRITICAL_TEMP_THRESHOLD / 100);
+		aqc111_data->thermal_throttling = 1;
+		reset_speed = 1;
+	}
+
+	if (reset_speed)
+		aqc111_set_phy_speed(dev, aqc111_data->autoneg,
+				     aqc111_data->advertised_speed);
+
+end:
+	schedule_delayed_work(&aqc111_data->therm_work, timeout);
+}
+
 static int aqc111_reset(struct usbnet *dev)
 {
 	struct aqc111_data *aqc111_data = dev->driver_priv;
@@ -1032,6 +1103,10 @@ static int aqc111_reset(struct usbnet *dev)
 	aqc111_set_phy_speed(dev, aqc111_data->autoneg,
 			     aqc111_data->advertised_speed);
 
+	INIT_DELAYED_WORK(&aqc111_data->therm_work, &aqc111_thermal_work_cb);
+	schedule_delayed_work(&aqc111_data->therm_work,
+			      msecs_to_jiffies(AQ_THERMAL_TIMER_MS));
+
 	return 0;
 }
 
@@ -1040,6 +1115,9 @@ static int aqc111_stop(struct usbnet *dev)
 	struct aqc111_data *aqc111_data = dev->driver_priv;
 	u16 reg16 = 0;
 
+	cancel_delayed_work_sync(&aqc111_data->therm_work);
+	aqc111_data->thermal_throttling = 0;
+
 	aqc111_read16_cmd(dev, AQ_ACCESS_MAC, SFR_MEDIUM_STATUS_MODE,
 			  2, &reg16);
 	reg16 &= ~SFR_MEDIUM_RECEIVE_EN;
diff --git a/drivers/net/usb/aqc111.h b/drivers/net/usb/aqc111.h
index 359663635b49..7b50e3cd217b 100644
--- a/drivers/net/usb/aqc111.h
+++ b/drivers/net/usb/aqc111.h
@@ -35,6 +35,11 @@
 #define AQ_USB_PHY_SET_TIMEOUT		10000
 #define AQ_USB_SET_TIMEOUT		4000
 
+#define AQ_THERMAL_TIMER_MS		500
+/* Temperature thresholds in units 1/100 degree of Celsius */
+#define AQ_NORMAL_TEMP_THRESHOLD	8500
+#define AQ_CRITICAL_TEMP_THRESHOLD	10600
+
 /* Feature. ********************************************/
 #define AQ_SUPPORT_FEATURE	(NETIF_F_SG | NETIF_F_IP_CSUM |\
 				 NETIF_F_IPV6_CSUM | NETIF_F_RXCSUM |\
@@ -183,6 +188,9 @@ struct aqc111_data {
 	} fw_ver;
 	u32 phy_cfg;
 	u8 wol_flags;
+	struct delayed_work therm_work;
+	u8 thermal_throttling;
+	struct usbnet *dev;
 };
 
 #define AQ_LS_MASK		0x8000
-- 
2.17.1