[PATCH v2 0/5] r8152: Avoid writing garbage to the adapter's registers

[PATCH v2 0/5] r8152: Avoid writing garbage to the adapter's registers

[Douglas Anderson]

This series is the result of a cooperative debug effort between
Realtek and the ChromeOS team. On ChromeOS, we've noticed that Realtek
Ethernet adapters can sometimes get so wedged that even a reboot of
the host can't get them to enumerate again, assuming that the adapter
was on a powered hub and din't lose power when the host rebooted. This
is sometimes seen in the ChromeOS automated testing lab. The only way
to recover adapters in this state is to manually power cycle them.

I managed to reproduce one instance of this wedging (unknown if this
is truly related to what the test lab sees) by doing this:
1. Start a flood ping from a host to the device.
2. Drop the device into kdb.
3. Wait 90 seconds.
4. Resume from kdb (the "g" command).
5. Wait another 45 seconds.

Upon analysis, Realtek realized this was happening:

1. The Linux driver was getting a "Tx timeout" after resuming from kdb
   and then trying to reset itself.
2. As part of the reset, the Linux driver was attempting to do a
   read-modify-write of the adapter's registers.
3. The read would fail (due to a timeout) and the driver pretended
   that the register contained all 0xFFs. See commit f53a7ad18959
   ("r8152: Set memory to all 0xFFs on failed reg reads")
4. The driver would take this value of all 0xFFs, modify it, and
   attempt to write it back to the adapter.
5. By this time the USB channel seemed to recover and thus we'd
   successfully write a value that was mostly 0xFFs to the adpater.
6. The adapter didn't like this and would wedge itself.

Another Engineer also managed to reproduce wedging of the Realtek
Ethernet adpater during a reboot test on an AMD Chromebook. In that
case he was sometimes seeing -EPIPE returned from the control
transfers.

This patch series fixes both issues.

Changes in v2:
- ("Check for unplug in rtl_phy_patch_request()") new for v2.
- ("Check for unplug in r8153b_ups_en() / r8153c_ups_en()") new for v2.
- ("Rename RTL8152_UNPLUG to RTL8152_INACCESSIBLE") new for v2.

Douglas Anderson (5):
  r8152: Increase USB control msg timeout to 5000ms as per spec
  r8152: Check for unplug in rtl_phy_patch_request()
  r8152: Check for unplug in r8153b_ups_en() / r8153c_ups_en()
  r8152: Rename RTL8152_UNPLUG to RTL8152_INACCESSIBLE
  r8152: Block future register access if register access fails

 drivers/net/usb/r8152.c | 268 +++++++++++++++++++++++++++++++---------
 1 file changed, 209 insertions(+), 59 deletions(-)

-- 
2.42.0.582.g8ccd20d70d-goog

[PATCH v2 1/5] r8152: Increase USB control msg timeout to 5000ms as per spec

[Douglas Anderson]

According to the comment next to USB_CTRL_GET_TIMEOUT and
USB_CTRL_SET_TIMEOUT, although sending/receiving control messages is
usually quite fast, the spec allows them to take up to 5 seconds.
Let's increase the timeout in the Realtek driver from 500ms to 5000ms
(using the #defines) to account for this.

This is not just a theoretical change. The need for the longer timeout
was seen in testing. Specifically, if you drop a sc7180-trogdor based
Chromebook into the kdb debugger and then "go" again after sitting in
the debugger for a while, the next USB control message takes a long
time. Out of ~40 tests the slowest USB control message was 4.5
seconds.

While dropping into kdb is not exactly an end-user scenario, the above
is similar to what could happen due to an temporary interrupt storm,
what could happen if there was a host controller (HW or SW) issue, or
what could happen if the Realtek device got into a confused state and
needed time to recover.

This change is fairly critical since the r8152 driver in Linux doesn't
expect register reads/writes (which are backed by USB control
messages) to fail.

Fixes: ac718b69301c ("net/usb: new driver for RTL8152")
Suggested-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

(no changes since v1)

 drivers/net/usb/r8152.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 0c13d9950cd8..482957beae66 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -1212,7 +1212,7 @@ int get_registers(struct r8152 *tp, u16 value, u16 index, u16 size, void *data)
 
 	ret = usb_control_msg(tp->udev, tp->pipe_ctrl_in,
 			      RTL8152_REQ_GET_REGS, RTL8152_REQT_READ,
-			      value, index, tmp, size, 500);
+			      value, index, tmp, size, USB_CTRL_GET_TIMEOUT);
 	if (ret < 0)
 		memset(data, 0xff, size);
 	else
@@ -1235,7 +1235,7 @@ int set_registers(struct r8152 *tp, u16 value, u16 index, u16 size, void *data)
 
 	ret = usb_control_msg(tp->udev, tp->pipe_ctrl_out,
 			      RTL8152_REQ_SET_REGS, RTL8152_REQT_WRITE,
-			      value, index, tmp, size, 500);
+			      value, index, tmp, size, USB_CTRL_SET_TIMEOUT);
 
 	kfree(tmp);
 
@@ -9494,7 +9494,8 @@ static u8 __rtl_get_hw_ver(struct usb_device *udev)
 
 	ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
 			      RTL8152_REQ_GET_REGS, RTL8152_REQT_READ,
-			      PLA_TCR0, MCU_TYPE_PLA, tmp, sizeof(*tmp), 500);
+			      PLA_TCR0, MCU_TYPE_PLA, tmp, sizeof(*tmp),
+			      USB_CTRL_GET_TIMEOUT);
 	if (ret > 0)
 		ocp_data = (__le32_to_cpu(*tmp) >> 16) & VERSION_MASK;
 
-- 
2.42.0.582.g8ccd20d70d-goog

[PATCH v2 2/5] r8152: Check for unplug in rtl_phy_patch_request()

[Douglas Anderson]

If the adapter is unplugged while we're looping in
rtl_phy_patch_request() we could end up looping for 10 seconds (2 ms *
5000 loops). Add code similar to what's done in other places in the
driver to check for unplug and bail.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v2:
- ("Check for unplug in rtl_phy_patch_request()") new for v2.

 drivers/net/usb/r8152.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 482957beae66..fff2f9e67b5f 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -4046,6 +4046,9 @@ static int rtl_phy_patch_request(struct r8152 *tp, bool request, bool wait)
 	for (i = 0; wait && i < 5000; i++) {
 		u32 ocp_data;
 
+		if (test_bit(RTL8152_UNPLUG, &tp->flags))
+			break;
+
 		usleep_range(1000, 2000);
 		ocp_data = ocp_reg_read(tp, OCP_PHY_PATCH_STAT);
 		if ((ocp_data & PATCH_READY) ^ check)
-- 
2.42.0.582.g8ccd20d70d-goog

[PATCH v2 3/5] r8152: Check for unplug in r8153b_ups_en() / r8153c_ups_en()

[Douglas Anderson]

If the adapter is unplugged while we're looping in r8153b_ups_en() /
r8153c_ups_en() we could end up looping for 10 seconds (20 ms * 500
loops). Add code similar to what's done in other places in the driver
to check for unplug and bail.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v2:
- ("Check for unplug in r8153b_ups_en() / r8153c_ups_en()") new for v2.

 drivers/net/usb/r8152.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index fff2f9e67b5f..888d3884821e 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -3663,6 +3663,8 @@ static void r8153b_ups_en(struct r8152 *tp, bool enable)
 			int i;
 
 			for (i = 0; i < 500; i++) {
+				if (test_bit(RTL8152_UNPLUG, &tp->flags))
+					return;
 				if (ocp_read_word(tp, MCU_TYPE_PLA, PLA_BOOT_CTRL) &
 				    AUTOLOAD_DONE)
 					break;
@@ -3703,6 +3705,8 @@ static void r8153c_ups_en(struct r8152 *tp, bool enable)
 			int i;
 
 			for (i = 0; i < 500; i++) {
+				if (test_bit(RTL8152_UNPLUG, &tp->flags))
+					return;
 				if (ocp_read_word(tp, MCU_TYPE_PLA, PLA_BOOT_CTRL) &
 				    AUTOLOAD_DONE)
 					break;
-- 
2.42.0.582.g8ccd20d70d-goog

[PATCH v2 4/5] r8152: Rename RTL8152_UNPLUG to RTL8152_INACCESSIBLE

[Douglas Anderson]

Whenever the RTL8152_UNPLUG is set that just tells the driver that all
accesses will fail and we should just immediately bail. A future patch
will use this same concept at a time when the driver hasn't actually
been unplugged but is about to be reset. Rename the flag in
preparation for the future patch.

This is a no-op change and just a search and replace.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v2:
- ("Rename RTL8152_UNPLUG to RTL8152_INACCESSIBLE") new for v2.

 drivers/net/usb/r8152.c | 96 ++++++++++++++++++++---------------------
 1 file changed, 48 insertions(+), 48 deletions(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 888d3884821e..151c3c383080 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -764,7 +764,7 @@ enum rtl_register_content {
 
 /* rtl8152 flags */
 enum rtl8152_flags {
-	RTL8152_UNPLUG = 0,
+	RTL8152_INACCESSIBLE = 0,
 	RTL8152_SET_RX_MODE,
 	WORK_ENABLE,
 	RTL8152_LINK_CHG,
@@ -1245,7 +1245,7 @@ int set_registers(struct r8152 *tp, u16 value, u16 index, u16 size, void *data)
 static void rtl_set_unplug(struct r8152 *tp)
 {
 	if (tp->udev->state == USB_STATE_NOTATTACHED) {
-		set_bit(RTL8152_UNPLUG, &tp->flags);
+		set_bit(RTL8152_INACCESSIBLE, &tp->flags);
 		smp_mb__after_atomic();
 	}
 }
@@ -1256,7 +1256,7 @@ static int generic_ocp_read(struct r8152 *tp, u16 index, u16 size,
 	u16 limit = 64;
 	int ret = 0;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return -ENODEV;
 
 	/* both size and indix must be 4 bytes align */
@@ -1300,7 +1300,7 @@ static int generic_ocp_write(struct r8152 *tp, u16 index, u16 byteen,
 	u16 byteen_start, byteen_end, byen;
 	u16 limit = 512;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return -ENODEV;
 
 	/* both size and indix must be 4 bytes align */
@@ -1537,7 +1537,7 @@ static int read_mii_word(struct net_device *netdev, int phy_id, int reg)
 	struct r8152 *tp = netdev_priv(netdev);
 	int ret;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return -ENODEV;
 
 	if (phy_id != R8152_PHY_ID)
@@ -1553,7 +1553,7 @@ void write_mii_word(struct net_device *netdev, int phy_id, int reg, int val)
 {
 	struct r8152 *tp = netdev_priv(netdev);
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	if (phy_id != R8152_PHY_ID)
@@ -1758,7 +1758,7 @@ static void read_bulk_callback(struct urb *urb)
 	if (!tp)
 		return;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	if (!test_bit(WORK_ENABLE, &tp->flags))
@@ -1850,7 +1850,7 @@ static void write_bulk_callback(struct urb *urb)
 	if (!test_bit(WORK_ENABLE, &tp->flags))
 		return;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	if (!skb_queue_empty(&tp->tx_queue))
@@ -1871,7 +1871,7 @@ static void intr_callback(struct urb *urb)
 	if (!test_bit(WORK_ENABLE, &tp->flags))
 		return;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	switch (status) {
@@ -2615,7 +2615,7 @@ static void bottom_half(struct tasklet_struct *t)
 {
 	struct r8152 *tp = from_tasklet(tp, t, tx_tl);
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	if (!test_bit(WORK_ENABLE, &tp->flags))
@@ -2658,7 +2658,7 @@ int r8152_submit_rx(struct r8152 *tp, struct rx_agg *agg, gfp_t mem_flags)
 	int ret;
 
 	/* The rx would be stopped, so skip submitting */
-	if (test_bit(RTL8152_UNPLUG, &tp->flags) ||
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags) ||
 	    !test_bit(WORK_ENABLE, &tp->flags) || !netif_carrier_ok(tp->netdev))
 		return 0;
 
@@ -3058,7 +3058,7 @@ static int rtl_enable(struct r8152 *tp)
 
 static int rtl8152_enable(struct r8152 *tp)
 {
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return -ENODEV;
 
 	set_tx_qlen(tp);
@@ -3145,7 +3145,7 @@ static int rtl8153_enable(struct r8152 *tp)
 {
 	u32 ocp_data;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return -ENODEV;
 
 	set_tx_qlen(tp);
@@ -3177,7 +3177,7 @@ static void rtl_disable(struct r8152 *tp)
 	u32 ocp_data;
 	int i;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags)) {
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags)) {
 		rtl_drop_queued_tx(tp);
 		return;
 	}
@@ -3631,7 +3631,7 @@ static u16 r8153_phy_status(struct r8152 *tp, u16 desired)
 		}
 
 		msleep(20);
-		if (test_bit(RTL8152_UNPLUG, &tp->flags))
+		if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 			break;
 	}
 
@@ -3663,7 +3663,7 @@ static void r8153b_ups_en(struct r8152 *tp, bool enable)
 			int i;
 
 			for (i = 0; i < 500; i++) {
-				if (test_bit(RTL8152_UNPLUG, &tp->flags))
+				if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 					return;
 				if (ocp_read_word(tp, MCU_TYPE_PLA, PLA_BOOT_CTRL) &
 				    AUTOLOAD_DONE)
@@ -3705,7 +3705,7 @@ static void r8153c_ups_en(struct r8152 *tp, bool enable)
 			int i;
 
 			for (i = 0; i < 500; i++) {
-				if (test_bit(RTL8152_UNPLUG, &tp->flags))
+				if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 					return;
 				if (ocp_read_word(tp, MCU_TYPE_PLA, PLA_BOOT_CTRL) &
 				    AUTOLOAD_DONE)
@@ -4050,8 +4050,8 @@ static int rtl_phy_patch_request(struct r8152 *tp, bool request, bool wait)
 	for (i = 0; wait && i < 5000; i++) {
 		u32 ocp_data;
 
-		if (test_bit(RTL8152_UNPLUG, &tp->flags))
-			break;
+		if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
+			return -ENODEV;
 
 		usleep_range(1000, 2000);
 		ocp_data = ocp_reg_read(tp, OCP_PHY_PATCH_STAT);
@@ -6009,7 +6009,7 @@ static int rtl8156_enable(struct r8152 *tp)
 	u32 ocp_data;
 	u16 speed;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return -ENODEV;
 
 	r8156_fc_parameter(tp);
@@ -6067,7 +6067,7 @@ static int rtl8156b_enable(struct r8152 *tp)
 	u32 ocp_data;
 	u16 speed;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return -ENODEV;
 
 	set_tx_qlen(tp);
@@ -6253,7 +6253,7 @@ static int rtl8152_set_speed(struct r8152 *tp, u8 autoneg, u32 speed, u8 duplex,
 
 static void rtl8152_up(struct r8152 *tp)
 {
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	r8152_aldps_en(tp, false);
@@ -6263,7 +6263,7 @@ static void rtl8152_up(struct r8152 *tp)
 
 static void rtl8152_down(struct r8152 *tp)
 {
-	if (test_bit(RTL8152_UNPLUG, &tp->flags)) {
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags)) {
 		rtl_drop_queued_tx(tp);
 		return;
 	}
@@ -6278,7 +6278,7 @@ static void rtl8153_up(struct r8152 *tp)
 {
 	u32 ocp_data;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	r8153_u1u2en(tp, false);
@@ -6318,7 +6318,7 @@ static void rtl8153_down(struct r8152 *tp)
 {
 	u32 ocp_data;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags)) {
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags)) {
 		rtl_drop_queued_tx(tp);
 		return;
 	}
@@ -6339,7 +6339,7 @@ static void rtl8153b_up(struct r8152 *tp)
 {
 	u32 ocp_data;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	r8153b_u1u2en(tp, false);
@@ -6363,7 +6363,7 @@ static void rtl8153b_down(struct r8152 *tp)
 {
 	u32 ocp_data;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags)) {
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags)) {
 		rtl_drop_queued_tx(tp);
 		return;
 	}
@@ -6400,7 +6400,7 @@ static void rtl8153c_up(struct r8152 *tp)
 {
 	u32 ocp_data;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	r8153b_u1u2en(tp, false);
@@ -6481,7 +6481,7 @@ static void rtl8156_up(struct r8152 *tp)
 {
 	u32 ocp_data;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	r8153b_u1u2en(tp, false);
@@ -6554,7 +6554,7 @@ static void rtl8156_down(struct r8152 *tp)
 {
 	u32 ocp_data;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags)) {
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags)) {
 		rtl_drop_queued_tx(tp);
 		return;
 	}
@@ -6692,7 +6692,7 @@ static void rtl_work_func_t(struct work_struct *work)
 	/* If the device is unplugged or !netif_running(), the workqueue
 	 * doesn't need to wake the device, and could return directly.
 	 */
-	if (test_bit(RTL8152_UNPLUG, &tp->flags) || !netif_running(tp->netdev))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags) || !netif_running(tp->netdev))
 		return;
 
 	if (usb_autopm_get_interface(tp->intf) < 0)
@@ -6731,7 +6731,7 @@ static void rtl_hw_phy_work_func_t(struct work_struct *work)
 {
 	struct r8152 *tp = container_of(work, struct r8152, hw_phy_work.work);
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	if (usb_autopm_get_interface(tp->intf) < 0)
@@ -6858,7 +6858,7 @@ static int rtl8152_close(struct net_device *netdev)
 	netif_stop_queue(netdev);
 
 	res = usb_autopm_get_interface(tp->intf);
-	if (res < 0 || test_bit(RTL8152_UNPLUG, &tp->flags)) {
+	if (res < 0 || test_bit(RTL8152_INACCESSIBLE, &tp->flags)) {
 		rtl_drop_queued_tx(tp);
 		rtl_stop_rx(tp);
 	} else {
@@ -6891,7 +6891,7 @@ static void r8152b_init(struct r8152 *tp)
 	u32 ocp_data;
 	u16 data;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	data = r8152_mdio_read(tp, MII_BMCR);
@@ -6935,7 +6935,7 @@ static void r8153_init(struct r8152 *tp)
 	u16 data;
 	int i;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	r8153_u1u2en(tp, false);
@@ -6946,7 +6946,7 @@ static void r8153_init(struct r8152 *tp)
 			break;
 
 		msleep(20);
-		if (test_bit(RTL8152_UNPLUG, &tp->flags))
+		if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 			break;
 	}
 
@@ -7075,7 +7075,7 @@ static void r8153b_init(struct r8152 *tp)
 	u16 data;
 	int i;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	r8153b_u1u2en(tp, false);
@@ -7086,7 +7086,7 @@ static void r8153b_init(struct r8152 *tp)
 			break;
 
 		msleep(20);
-		if (test_bit(RTL8152_UNPLUG, &tp->flags))
+		if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 			break;
 	}
 
@@ -7157,7 +7157,7 @@ static void r8153c_init(struct r8152 *tp)
 	u16 data;
 	int i;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	r8153b_u1u2en(tp, false);
@@ -7177,7 +7177,7 @@ static void r8153c_init(struct r8152 *tp)
 			break;
 
 		msleep(20);
-		if (test_bit(RTL8152_UNPLUG, &tp->flags))
+		if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 			return;
 	}
 
@@ -8006,7 +8006,7 @@ static void r8156_init(struct r8152 *tp)
 	u16 data;
 	int i;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	ocp_data = ocp_read_byte(tp, MCU_TYPE_USB, USB_ECM_OP);
@@ -8027,7 +8027,7 @@ static void r8156_init(struct r8152 *tp)
 			break;
 
 		msleep(20);
-		if (test_bit(RTL8152_UNPLUG, &tp->flags))
+		if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 			return;
 	}
 
@@ -8102,7 +8102,7 @@ static void r8156b_init(struct r8152 *tp)
 	u16 data;
 	int i;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	ocp_data = ocp_read_byte(tp, MCU_TYPE_USB, USB_ECM_OP);
@@ -8136,7 +8136,7 @@ static void r8156b_init(struct r8152 *tp)
 			break;
 
 		msleep(20);
-		if (test_bit(RTL8152_UNPLUG, &tp->flags))
+		if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 			return;
 	}
 
@@ -9165,7 +9165,7 @@ static int rtl8152_ioctl(struct net_device *netdev, struct ifreq *rq, int cmd)
 	struct mii_ioctl_data *data = if_mii(rq);
 	int res;
 
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return -ENODEV;
 
 	res = usb_autopm_get_interface(tp->intf);
@@ -9267,7 +9267,7 @@ static const struct net_device_ops rtl8152_netdev_ops = {
 
 static void rtl8152_unload(struct r8152 *tp)
 {
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	if (tp->version != RTL_VER_01)
@@ -9276,7 +9276,7 @@ static void rtl8152_unload(struct r8152 *tp)
 
 static void rtl8153_unload(struct r8152 *tp)
 {
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	r8153_power_cut_en(tp, false);
@@ -9284,7 +9284,7 @@ static void rtl8153_unload(struct r8152 *tp)
 
 static void rtl8153b_unload(struct r8152 *tp)
 {
-	if (test_bit(RTL8152_UNPLUG, &tp->flags))
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
 
 	r8153b_power_cut_en(tp, false);
-- 
2.42.0.582.g8ccd20d70d-goog

[PATCH v2 5/5] r8152: Block future register access if register access fails

[Douglas Anderson]

Even though the functions to read/write registers can fail, most of
the places in the r8152 driver that read/write register values don't
check error codes. The lack of error code checking is problematic in
at least two ways.

The first problem is that the r8152 driver often uses code patterns
similar to this:
  x = read_register()
  x = x | SOME_BIT;
  write_register(x);

...with the above pattern, if the read_register() fails and returns
garbage then we'll end up trying to write modified garbage back to the
Realtek adapter. If the write_register() succeeds that's bad. Note
that as of commit f53a7ad18959 ("r8152: Set memory to all 0xFFs on
failed reg reads") the "garbage" returned by read_register() will at
least be consistent garbage, but it is still garbage.

It turns out that this problem is very serious. Writing garbage to
some of the hardware registers on the Ethernet adapter can put the
adapter in such a bad state that it needs to be power cycled (fully
unplugged and plugged in again) before it can enumerate again.

The second problem is that the r8152 driver generally has functions
that are long sequences of register writes. Assuming everything will
be OK if a random register write fails in the middle isn't a great
assumption.

One might wonder if the above two problems are real. You could ask if
we would really have a successful write after a failed read. It turns
out that the answer appears to be "yes, this can happen". In fact,
we've seen at least two distinct failure modes where this happens.

On a sc7180-trogdor Chromebook if you drop into kdb for a while and
then resume, you can see:
1. We get a "Tx timeout"
2. The "Tx timeout" queues up a USB reset.
3. In rtl8152_pre_reset() we try to reinit the hardware.
4. The first several (2-9) register accesses fail with a timeout, then
   things recover.

The above test case was actually fixed by the patch ("r8152: Increase
USB control msg timeout to 5000ms as per spec") but at least shows
that we really can see successful calls after failed ones.

On a different (AMD) based Chromebook with a particular adapter, we
found that during reboot tests we'd also sometimes get a transitory
failure. In this case we saw -EPIPE being returned sometimes. Retrying
worked, but retrying is not always safe for all register accesses
since reading/writing some registers might have side effects (like
registers that clear on read).

Let's fully lock out all register access if a register access fails.
When we do this, we'll try to queue up a USB reset and try to unlock
register access after the reset. This is slightly tricker than it
sounds since the r8152 driver has an optimized reset sequence that
only works reliably after probe happens. In order to handle this, we
avoid the optimized reset if probe didn't finish.

When locking out access, we'll use the existing infrastructure that
the driver was using when it detected we were unplugged. This keeps us
from getting stuck in delay loops in some parts of the driver.

- Reset patch no longer based on retry patch, since that was dropped.
- Reset patch should be robust even if failures happen in probe.
- Switched booleans to bits in the "flags" variable.
- Check for -ENODEV instead of "udev->state == USB_STATE_NOTATTACHED"

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
Originally when looking at this problem I thought that the obvious
solution was to "just" add better error handling to the driver. This
_sounds_ appealing, but it's a massive change and touches a
significant portion of the lines in this driver. It's also not always
obvious what the driver should be doing to handle errors.

(no changes since v1)

 drivers/net/usb/r8152.c | 176 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 159 insertions(+), 17 deletions(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 151c3c383080..ec9f4973f150 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -773,6 +773,8 @@ enum rtl8152_flags {
 	SCHEDULE_TASKLET,
 	GREEN_ETHERNET,
 	RX_EPROTO,
+	IN_PRE_RESET,
+	PROBED_WITH_NO_ERRORS,
 };
 
 #define DEVICE_ID_LENOVO_USB_C_TRAVEL_HUB		0x721e
@@ -953,6 +955,8 @@ struct r8152 {
 	u8 version;
 	u8 duplex;
 	u8 autoneg;
+
+	unsigned int reg_access_reset_count;
 };
 
 /**
@@ -1200,6 +1204,91 @@ static unsigned int agg_buf_sz = 16384;
 
 #define RTL_LIMITED_TSO_SIZE	(size_to_mtu(agg_buf_sz) - sizeof(struct tx_desc))
 
+/* If register access fails then we block access and issue a reset. If this
+ * happens too many times in a row without a successful access then we stop
+ * trying to reset and just leave access blocked.
+ */
+#define REGISTER_ACCESS_MAX_RESETS	3
+
+static void rtl_set_inaccessible(struct r8152 *tp)
+{
+	set_bit(RTL8152_INACCESSIBLE, &tp->flags);
+	smp_mb__after_atomic();
+}
+
+static void rtl_set_accessible(struct r8152 *tp)
+{
+	clear_bit(RTL8152_INACCESSIBLE, &tp->flags);
+	smp_mb__after_atomic();
+}
+
+static
+int r8152_control_msg(struct r8152 *tp, unsigned int pipe, __u8 request,
+		      __u8 requesttype, __u16 value, __u16 index, void *data,
+		      __u16 size, const char *msg_tag)
+{
+	struct usb_device *udev = tp->udev;
+	int ret;
+
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
+		return -ENODEV;
+
+	ret = usb_control_msg(udev, pipe, request, requesttype,
+			      value, index, data, size,
+			      USB_CTRL_GET_TIMEOUT);
+
+	/* No need to issue a reset report an error if the USB device got
+	 * unplugged; just return immediately.
+	 */
+	if (ret == -ENODEV)
+		return ret;
+
+	/* If the write was successful then we're done */
+	if (ret >= 0) {
+		tp->reg_access_reset_count = 0;
+		return ret;
+	}
+
+	dev_err(&udev->dev,
+		"Failed to %s %d bytes at %#06x/%#06x (%d)\n",
+		msg_tag, size, value, index, ret);
+
+	/* Block all future register access until we reset. Much of the oode
+	 * in the driver doesn't check for errors. Notably, many parts of the
+	 * driver do a read/modify/write of a register value without
+	 * confirming that the read succeeded. Writing back modified garbage
+	 * like this can fully wedge the adapter, requiring a power cycle.
+	 */
+	rtl_set_inaccessible(tp);
+
+	/* Failing to access registers in pre-reset is not surprising since we
+	 * wouldn't be resetting if things were behaving normally. The register
+	 * access we do in pre-reset isn't truly mandatory--we're just reusing
+	 * the disable() function and trying to be nice by powering the
+	 * adapter down before resetting it. Thus, if we're in pre-reset,
+	 * we'll return right away and not try to queue up yet another reset.
+	 * We know the post-reset is already coming.
+	 *
+	 * We'll also return right away if we haven't finished probe. At the
+	 * end of probe we'll queue the reset just to make sure it doesn't
+	 * timeout.
+	 */
+	if (test_bit(IN_PRE_RESET, &tp->flags) ||
+	    !test_bit(PROBED_WITH_NO_ERRORS, &tp->flags))
+		return ret;
+
+	if (tp->reg_access_reset_count < REGISTER_ACCESS_MAX_RESETS) {
+		usb_queue_reset_device(tp->intf);
+		tp->reg_access_reset_count++;
+	} else if (tp->reg_access_reset_count == REGISTER_ACCESS_MAX_RESETS) {
+		dev_err(&udev->dev,
+			"Tried to reset %d times; giving up.\n",
+			REGISTER_ACCESS_MAX_RESETS);
+	}
+
+	return ret;
+}
+
 static
 int get_registers(struct r8152 *tp, u16 value, u16 index, u16 size, void *data)
 {
@@ -1210,9 +1299,10 @@ int get_registers(struct r8152 *tp, u16 value, u16 index, u16 size, void *data)
 	if (!tmp)
 		return -ENOMEM;
 
-	ret = usb_control_msg(tp->udev, tp->pipe_ctrl_in,
-			      RTL8152_REQ_GET_REGS, RTL8152_REQT_READ,
-			      value, index, tmp, size, USB_CTRL_GET_TIMEOUT);
+	ret = r8152_control_msg(tp, tp->pipe_ctrl_in,
+				RTL8152_REQ_GET_REGS, RTL8152_REQT_READ,
+				value, index, tmp, size, "read");
+
 	if (ret < 0)
 		memset(data, 0xff, size);
 	else
@@ -1233,9 +1323,9 @@ int set_registers(struct r8152 *tp, u16 value, u16 index, u16 size, void *data)
 	if (!tmp)
 		return -ENOMEM;
 
-	ret = usb_control_msg(tp->udev, tp->pipe_ctrl_out,
-			      RTL8152_REQ_SET_REGS, RTL8152_REQT_WRITE,
-			      value, index, tmp, size, USB_CTRL_SET_TIMEOUT);
+	ret = r8152_control_msg(tp, tp->pipe_ctrl_out,
+				RTL8152_REQ_SET_REGS, RTL8152_REQT_WRITE,
+				value, index, tmp, size, "write");
 
 	kfree(tmp);
 
@@ -1244,10 +1334,8 @@ int set_registers(struct r8152 *tp, u16 value, u16 index, u16 size, void *data)
 
 static void rtl_set_unplug(struct r8152 *tp)
 {
-	if (tp->udev->state == USB_STATE_NOTATTACHED) {
-		set_bit(RTL8152_INACCESSIBLE, &tp->flags);
-		smp_mb__after_atomic();
-	}
+	if (tp->udev->state == USB_STATE_NOTATTACHED)
+		rtl_set_inaccessible(tp);
 }
 
 static int generic_ocp_read(struct r8152 *tp, u16 index, u16 size,
@@ -8265,6 +8353,19 @@ static int rtl8152_pre_reset(struct usb_interface *intf)
 	if (!tp)
 		return 0;
 
+	/* We can only use the optimized reset if we made it to the end of
+	 * probe without any register access fails, which sets
+	 * `PROBED_WITH_NO_ERRORS` to true. If we didn't have that then return
+	 * an error here which tells the USB framework to fully unbind/rebind
+	 * our driver.
+	 */
+	mutex_lock(&tp->control);
+	if (!test_bit(PROBED_WITH_NO_ERRORS, &tp->flags)) {
+		mutex_unlock(&tp->control);
+		return -EIO;
+	}
+	mutex_unlock(&tp->control);
+
 	netdev = tp->netdev;
 	if (!netif_running(netdev))
 		return 0;
@@ -8277,7 +8378,9 @@ static int rtl8152_pre_reset(struct usb_interface *intf)
 	napi_disable(&tp->napi);
 	if (netif_carrier_ok(netdev)) {
 		mutex_lock(&tp->control);
+		set_bit(IN_PRE_RESET, &tp->flags);
 		tp->rtl_ops.disable(tp);
+		clear_bit(IN_PRE_RESET, &tp->flags);
 		mutex_unlock(&tp->control);
 	}
 
@@ -8293,6 +8396,10 @@ static int rtl8152_post_reset(struct usb_interface *intf)
 	if (!tp)
 		return 0;
 
+	mutex_lock(&tp->control);
+	rtl_set_accessible(tp);
+	mutex_unlock(&tp->control);
+
 	/* reset the MAC address in case of policy change */
 	if (determine_ethernet_addr(tp, &sa) >= 0) {
 		rtnl_lock();
@@ -9494,17 +9601,30 @@ static u8 __rtl_get_hw_ver(struct usb_device *udev)
 	__le32 *tmp;
 	u8 version;
 	int ret;
+	int i;
 
 	tmp = kmalloc(sizeof(*tmp), GFP_KERNEL);
 	if (!tmp)
 		return 0;
 
-	ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
-			      RTL8152_REQ_GET_REGS, RTL8152_REQT_READ,
-			      PLA_TCR0, MCU_TYPE_PLA, tmp, sizeof(*tmp),
-			      USB_CTRL_GET_TIMEOUT);
-	if (ret > 0)
-		ocp_data = (__le32_to_cpu(*tmp) >> 16) & VERSION_MASK;
+	/* Retry up to 3 times in case there is a transitory error. We do this
+	 * since retrying a read of the version is always safe and this
+	 * function doesn't take advantage of r8152_control_msg() which would
+	 * queue up a reset upon error.
+	 */
+	for (i = 0; i < 3; i++) {
+		ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
+				      RTL8152_REQ_GET_REGS, RTL8152_REQT_READ,
+				      PLA_TCR0, MCU_TYPE_PLA, tmp, sizeof(*tmp),
+				      USB_CTRL_GET_TIMEOUT);
+		if (ret > 0) {
+			ocp_data = (__le32_to_cpu(*tmp) >> 16) & VERSION_MASK;
+			break;
+		}
+	}
+
+	if (i != 0 && ret > 0)
+		dev_warn(&udev->dev, "Needed %d retries to read version\n", i);
 
 	kfree(tmp);
 
@@ -9784,7 +9904,29 @@ static int rtl8152_probe(struct usb_interface *intf,
 	else
 		device_set_wakeup_enable(&udev->dev, false);
 
-	netif_info(tp, probe, netdev, "%s\n", DRIVER_VERSION);
+	mutex_lock(&tp->control);
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags)) {
+		/* If the device is marked inaccessible before probe even
+		 * finished then one of two things happened. Either we got a
+		 * USB error during probe or the user already unplugged the
+		 * device.
+		 *
+		 * If we got a USB error during probe then we skipped doing a
+		 * reset in r8152_control_msg() and deferred it to here. This
+		 * is because the queued reset will give up after 1 second
+		 * (see usb_lock_device_for_reset()) and we want to make sure
+		 * that we queue things up right before probe finishes.
+		 *
+		 * If the user already unplugged the device then the USB
+		 * farmework will call unbind right away for us. The extra
+		 * reset we queue up here will be harmless.
+		 */
+		usb_queue_reset_device(tp->intf);
+	} else {
+		set_bit(PROBED_WITH_NO_ERRORS, &tp->flags);
+		netif_info(tp, probe, netdev, "%s\n", DRIVER_VERSION);
+	}
+	mutex_unlock(&tp->control);
 
 	return 0;
 
-- 
2.42.0.582.g8ccd20d70d-goog

Re: [PATCH v2 5/5] r8152: Block future register access if register access fails

[Doug Anderson]

Hi,

On Wed, Oct 4, 2023 at 12:27 PM Douglas Anderson <dianders@chromium.org> wrote:
>
> Even though the functions to read/write registers can fail, most of
> the places in the r8152 driver that read/write register values don't
> check error codes. The lack of error code checking is problematic in
> at least two ways.
>
> The first problem is that the r8152 driver often uses code patterns
> similar to this:
>   x = read_register()
>   x = x | SOME_BIT;
>   write_register(x);
>
> ...with the above pattern, if the read_register() fails and returns
> garbage then we'll end up trying to write modified garbage back to the
> Realtek adapter. If the write_register() succeeds that's bad. Note
> that as of commit f53a7ad18959 ("r8152: Set memory to all 0xFFs on
> failed reg reads") the "garbage" returned by read_register() will at
> least be consistent garbage, but it is still garbage.
>
> It turns out that this problem is very serious. Writing garbage to
> some of the hardware registers on the Ethernet adapter can put the
> adapter in such a bad state that it needs to be power cycled (fully
> unplugged and plugged in again) before it can enumerate again.
>
> The second problem is that the r8152 driver generally has functions
> that are long sequences of register writes. Assuming everything will
> be OK if a random register write fails in the middle isn't a great
> assumption.
>
> One might wonder if the above two problems are real. You could ask if
> we would really have a successful write after a failed read. It turns
> out that the answer appears to be "yes, this can happen". In fact,
> we've seen at least two distinct failure modes where this happens.
>
> On a sc7180-trogdor Chromebook if you drop into kdb for a while and
> then resume, you can see:
> 1. We get a "Tx timeout"
> 2. The "Tx timeout" queues up a USB reset.
> 3. In rtl8152_pre_reset() we try to reinit the hardware.
> 4. The first several (2-9) register accesses fail with a timeout, then
>    things recover.
>
> The above test case was actually fixed by the patch ("r8152: Increase
> USB control msg timeout to 5000ms as per spec") but at least shows
> that we really can see successful calls after failed ones.
>
> On a different (AMD) based Chromebook with a particular adapter, we
> found that during reboot tests we'd also sometimes get a transitory
> failure. In this case we saw -EPIPE being returned sometimes. Retrying
> worked, but retrying is not always safe for all register accesses
> since reading/writing some registers might have side effects (like
> registers that clear on read).
>
> Let's fully lock out all register access if a register access fails.
> When we do this, we'll try to queue up a USB reset and try to unlock
> register access after the reset. This is slightly tricker than it
> sounds since the r8152 driver has an optimized reset sequence that
> only works reliably after probe happens. In order to handle this, we
> avoid the optimized reset if probe didn't finish.
>
> When locking out access, we'll use the existing infrastructure that
> the driver was using when it detected we were unplugged. This keeps us
> from getting stuck in delay loops in some parts of the driver.
>
> - Reset patch no longer based on retry patch, since that was dropped.
> - Reset patch should be robust even if failures happen in probe.
> - Switched booleans to bits in the "flags" variable.
> - Check for -ENODEV instead of "udev->state == USB_STATE_NOTATTACHED"

Argh, the above 4 bullet points were supposed to get moved "after the
cut" and describe the differences between v1 and v2. Sorry! :(

To avoid spamming people, I won't send another version and will wait
for feedback. I'm happy to fix and send a new version at any time,
though.

Re: [PATCH v2 5/5] r8152: Block future register access if register access fails

[Simon Horman]

On Wed, Oct 04, 2023 at 12:24:42PM -0700, Douglas Anderson wrote:

...

> @@ -9784,7 +9904,29 @@ static int rtl8152_probe(struct usb_interface *intf,
>  	else
>  		device_set_wakeup_enable(&udev->dev, false);
>  
> -	netif_info(tp, probe, netdev, "%s\n", DRIVER_VERSION);
> +	mutex_lock(&tp->control);
> +	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags)) {
> +		/* If the device is marked inaccessible before probe even
> +		 * finished then one of two things happened. Either we got a
> +		 * USB error during probe or the user already unplugged the
> +		 * device.
> +		 *
> +		 * If we got a USB error during probe then we skipped doing a
> +		 * reset in r8152_control_msg() and deferred it to here. This
> +		 * is because the queued reset will give up after 1 second
> +		 * (see usb_lock_device_for_reset()) and we want to make sure
> +		 * that we queue things up right before probe finishes.
> +		 *
> +		 * If the user already unplugged the device then the USB
> +		 * farmework will call unbind right away for us. The extra

Hi Douglas,

As you are planning to re-spin anyway: farmework -> framework

> +		 * reset we queue up here will be harmless.
> +		 */
> +		usb_queue_reset_device(tp->intf);
> +	} else {
> +		set_bit(PROBED_WITH_NO_ERRORS, &tp->flags);
> +		netif_info(tp, probe, netdev, "%s\n", DRIVER_VERSION);
> +	}
> +	mutex_unlock(&tp->control);
>  
>  	return 0;
>  
> -- 
> 2.42.0.582.g8ccd20d70d-goog
>