[PATCH 1/3] [media] mceusb: RX -EPIPE (urb status = -32) lockup failure fix

[A Sun <as1033x@comcast.net>]

commit https://github.com/asunxx/linux/commit/17fe3b51f4ad5202a876ea4c92b5d99d4e166823
Author: A Sun <as1033x@comcast.net>
Date:   Sun, 26 Mar 2017 13:24:18 -0400 

Bug:

RX -EPIPE failure with infinite loop and flooding of
Mar 20 22:24:56 raspberrypi kernel: [ 2851.966506] mceusb 1-1.2:1.0: Error: urb status = -32
log message at 8000 messages per second.
Bug trigger appears to be normal, but heavy, IR receiver use.
Driver and Linux host become unusable after error.
Also seen at https://sourceforge.net/p/lirc/mailman/message/34886165/

Fix:

Message reports RX usb halt (stall) condition requiring usb_clear_halt() call in non-interrupt context to recover.
Add driver workqueue call to perform this recovery based on method in use for the usbnet device driver.

Tested with:

Linux raspberrypi 4.4.50-v7+ #970 SMP Mon Feb 20 19:18:29 GMT 2017 armv7l GNU/Linux
mceusb 1-1.2:1.0: Registered Pinnacle Systems PCTV Remote USB with mce emulator interface version 1
mceusb 1-1.2:1.0: 2 tx ports (0x1 cabled) and 2 rx sensors (0x1 active)

Signed-off-by: A Sun <as1033x@comcast.net>
---
 drivers/media/rc/mceusb.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 66 insertions(+), 1 deletion(-)

diff --git a/drivers/media/rc/mceusb.c b/drivers/media/rc/mceusb.c
index 238d8ea..7b6f9e5 100644
--- a/drivers/media/rc/mceusb.c
+++ b/drivers/media/rc/mceusb.c
@@ -36,12 +36,13 @@
 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/workqueue.h>
 #include <linux/usb.h>
 #include <linux/usb/input.h>
 #include <linux/pm_wakeup.h>
 #include <media/rc-core.h>
 
-#define DRIVER_VERSION	"1.92"
+#define DRIVER_VERSION	"1.93"
 #define DRIVER_AUTHOR	"Jarod Wilson <jarod@redhat.com>"
 #define DRIVER_DESC	"Windows Media Center Ed. eHome Infrared Transceiver " \
 			"device driver"
@@ -417,6 +418,7 @@ struct mceusb_dev {
 	/* usb */
 	struct usb_device *usbdev;
 	struct urb *urb_in;
+	unsigned int pipe_in;
 	struct usb_endpoint_descriptor *usb_ep_out;
 
 	/* buffers and dma */
@@ -454,6 +456,12 @@ struct mceusb_dev {
 	u8 num_rxports;		/* number of receive sensors */
 	u8 txports_cabled;	/* bitmask of transmitters with cable */
 	u8 rxports_active;	/* bitmask of active receive sensors */
+
+	/* kevent support */
+	struct work_struct kevent;
+	unsigned long kevent_flags;
+#		define EVENT_TX_HALT	0
+#		define EVENT_RX_HALT	1
 };
 
 /* MCE Device Command Strings, generally a port and command pair */
@@ -1025,6 +1033,23 @@ static void mceusb_process_ir_data(struct mceusb_dev *ir, int buf_len)
 	}
 }
 
+/*
+ * Workqueue task dispatcher
+ * for work that can't be done in interrupt handlers
+ * (mceusb_dev_recv() and mce_async_callback()) nor tasklets.
+ * Invokes mceusb_deferred_kevent() for recovering from
+ * error events specified by the kevent bit field.
+ */
+static void mceusb_defer_kevent(struct mceusb_dev *ir, int kevent)
+{
+	set_bit(kevent, &ir->kevent_flags);
+	if (!schedule_work(&ir->kevent)) {
+		dev_err(ir->dev, "kevent %d may have been dropped", kevent);
+	} else {
+		dev_dbg(ir->dev, "kevent %d scheduled", kevent);
+	}
+}
+
 static void mceusb_dev_recv(struct urb *urb)
 {
 	struct mceusb_dev *ir;
@@ -1052,6 +1077,11 @@ static void mceusb_dev_recv(struct urb *urb)
 		return;
 
 	case -EPIPE:
+		dev_err(ir->dev, "Error: urb status = %d (RX HALT)",
+			urb->status);
+		mceusb_defer_kevent(ir, EVENT_RX_HALT);
+		return;
+
 	default:
 		dev_err(ir->dev, "Error: urb status = %d", urb->status);
 		break;
@@ -1170,6 +1200,37 @@ static void mceusb_flash_led(struct mceusb_dev *ir)
 	mce_async_out(ir, FLASH_LED, sizeof(FLASH_LED));
 }
 
+/*
+ * Workqueue function
+ * for resetting or recovering device after occurrence of error events
+ * specified in ir->kevent bit field.
+ * Function runs (via schedule_work()) in non-interrupt context, for
+ * calls here (such as usb_clear_halt()) requiring non-interrupt context.
+ */
+static void mceusb_deferred_kevent(struct work_struct *work)
+{
+	struct mceusb_dev *ir =
+		container_of(work, struct mceusb_dev, kevent);
+	int status;
+
+	if (test_bit(EVENT_RX_HALT, &ir->kevent_flags)) {
+		usb_unlink_urb(ir->urb_in);
+		status = usb_clear_halt(ir->usbdev, ir->pipe_in);
+		if (status < 0) {
+			dev_err(ir->dev, "rx clear halt error %d",
+				status);
+			return;
+		}
+		clear_bit(EVENT_RX_HALT, &ir->kevent_flags);
+		status = usb_submit_urb(ir->urb_in, GFP_KERNEL);
+		if (status < 0) {
+			dev_err(ir->dev, "rx unhalt submit urb error %d",
+				status);
+			return;
+		}
+	}
+}
+
 static struct rc_dev *mceusb_init_rc_dev(struct mceusb_dev *ir)
 {
 	struct usb_device *udev = ir->usbdev;
@@ -1336,6 +1397,9 @@ static int mceusb_dev_probe(struct usb_interface *intf,
 	if (!ir->rc)
 		goto rc_dev_fail;
 
+	ir->pipe_in = pipe;
+	INIT_WORK(&ir->kevent, mceusb_deferred_kevent);
+
 	/* wire up inbound data handler */
 	usb_fill_int_urb(ir->urb_in, dev, pipe, ir->buf_in, maxp,
 				mceusb_dev_recv, ir, ep_in->bInterval);
@@ -1405,6 +1469,7 @@ static void mceusb_dev_disconnect(struct usb_interface *intf)
 		return;
 
 	ir->usbdev = NULL;
+	cancel_work_sync(&ir->kevent);
 	rc_unregister_device(ir->rc);
 	usb_kill_urb(ir->urb_in);
 	usb_free_urb(ir->urb_in);
-- 
2.1.4