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Commit 9339eaf7 authored by Terin Stock's avatar Terin Stock Committed by Greg Kroah-Hartman
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usb: dwc2: host: use hrtimer for NAK retries 



commit 6ed30a7d8ec29d3aba46e47aa8b4a44f077dda4e upstream.

Modify the wait delay utilize the high resolution timer API to allow for
more precisely scheduled callbacks.

A previous commit added a 1ms retry delay after multiple consecutive
NAKed transactions using jiffies. On systems with a low timer interrupt
frequency, this delay may be significantly longer than specified,
resulting in misbehavior with some USB devices.

This scenario was reached on a Raspberry Pi 3B with a Macally FDD-USB
floppy drive (identified as 0424:0fdc Standard Microsystems Corp.
Floppy, based on the USB97CFDC USB FDC). With the relay delay, the drive
would be unable to mount a disk, replying with NAKs until the device was
reset.

Using ktime, the delta between starting the timer (in dwc2_hcd_qh_add)
and the callback function can be determined. With the original delay
implementation, this value was consistently approximately 12ms. (output
in us).

    <idle>-0     [000] ..s.  1600.559974: dwc2_wait_timer_fn: wait_timer delta: 11976
    <idle>-0     [000] ..s.  1600.571974: dwc2_wait_timer_fn: wait_timer delta: 11977
    <idle>-0     [000] ..s.  1600.583974: dwc2_wait_timer_fn: wait_timer delta: 11976
    <idle>-0     [000] ..s.  1600.595974: dwc2_wait_timer_fn: wait_timer delta: 11977

After converting the relay delay to using a higher resolution timer, the
delay was much closer to 1ms.

    <idle>-0     [000] d.h.  1956.553017: dwc2_wait_timer_fn: wait_timer delta: 1002
    <idle>-0     [000] d.h.  1956.554114: dwc2_wait_timer_fn: wait_timer delta: 1002
    <idle>-0     [000] d.h.  1957.542660: dwc2_wait_timer_fn: wait_timer delta: 1004
    <idle>-0     [000] d.h.  1957.543701: dwc2_wait_timer_fn: wait_timer delta: 1002

The floppy drive operates properly with delays up to approximately 5ms,
and sends NAKs for any delays that are longer.

Fixes: 38d2b5fb ("usb: dwc2: host: Don't retry NAKed transactions right away")
Cc: <stable@vger.kernel.org>
Reviewed-by: default avatarDouglas Anderson <dianders@chromium.org>
Acked-by: default avatarMinas Harutyunyan <hminas@synopsys.com>
Signed-off-by: default avatarTerin Stock <terin@terinstock.com>
Signed-off-by: default avatarFelipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2c788295

drivers/usb/dwc2/hcd.h

+1 −1
Original line number Diff line number Diff line
@@ -366,7 +366,7 @@ struct dwc2_qh { 
	u32 desc_list_sz;

	u32 *n_bytes;

	struct timer_list unreserve_timer;

	struct timer_list wait_timer;

	struct hrtimer wait_timer;

	struct dwc2_tt *dwc_tt;

	int ttport;

	unsigned tt_buffer_dirty:1;

drivers/usb/dwc2/hcd_queue.c

+12 −7
Original line number Diff line number Diff line
@@ -59,7 +59,7 @@ 
#define DWC2_UNRESERVE_DELAY (msecs_to_jiffies(5))



/* If we get a NAK, wait this long before retrying */

#define DWC2_RETRY_WAIT_DELAY (msecs_to_jiffies(1))

#define DWC2_RETRY_WAIT_DELAY 1*1E6L



/**

 * dwc2_periodic_channel_available() - Checks that a channel is available for a
@@ -1464,10 +1464,12 @@ static void dwc2_deschedule_periodic(struct dwc2_hsotg *hsotg, 
 * qh back to the "inactive" list, then queues transactions.

 *

 * @t: Pointer to wait_timer in a qh.

 *

 * Return: HRTIMER_NORESTART to not automatically restart this timer.

 */

static void dwc2_wait_timer_fn(struct timer_list *t)

static enum hrtimer_restart dwc2_wait_timer_fn(struct hrtimer *t)

{

	struct dwc2_qh *qh = from_timer(qh, t, wait_timer);

	struct dwc2_qh *qh = container_of(t, struct dwc2_qh, wait_timer);

	struct dwc2_hsotg *hsotg = qh->hsotg;

	unsigned long flags;
@@ -1491,6 +1493,7 @@ static void dwc2_wait_timer_fn(struct timer_list *t) 
	}



	spin_unlock_irqrestore(&hsotg->lock, flags);

	return HRTIMER_NORESTART;

}



/**
@@ -1521,7 +1524,8 @@ static void dwc2_qh_init(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh, 
	/* Initialize QH */

	qh->hsotg = hsotg;

	timer_setup(&qh->unreserve_timer, dwc2_unreserve_timer_fn, 0);

	timer_setup(&qh->wait_timer, dwc2_wait_timer_fn, 0);

	hrtimer_init(&qh->wait_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

	qh->wait_timer.function = &dwc2_wait_timer_fn;

	qh->ep_type = ep_type;

	qh->ep_is_in = ep_is_in;
@@ -1690,7 +1694,7 @@ void dwc2_hcd_qh_free(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh) 
	 * won't do anything anyway, but we want it to finish before we free

	 * memory.

	 */

	del_timer_sync(&qh->wait_timer);

	hrtimer_cancel(&qh->wait_timer);



	dwc2_host_put_tt_info(hsotg, qh->dwc_tt);
@@ -1716,6 +1720,7 @@ int dwc2_hcd_qh_add(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh) 
{

	int status;

	u32 intr_mask;

	ktime_t delay;



	if (dbg_qh(qh))

		dev_vdbg(hsotg->dev, "%s()\n", __func__);
@@ -1734,8 +1739,8 @@ int dwc2_hcd_qh_add(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh) 
			list_add_tail(&qh->qh_list_entry,

				      &hsotg->non_periodic_sched_waiting);

			qh->wait_timer_cancel = false;

			mod_timer(&qh->wait_timer,

				  jiffies + DWC2_RETRY_WAIT_DELAY + 1);

			delay = ktime_set(0, DWC2_RETRY_WAIT_DELAY);

			hrtimer_start(&qh->wait_timer, delay, HRTIMER_MODE_REL);

		} else {

			list_add_tail(&qh->qh_list_entry,

				      &hsotg->non_periodic_sched_inactive);