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Date: Sun, 09 Sep 2018 21:24:31 -0700
From: Terin Stock <terin@...instock.com>
To: linux-usb@...r.kernel.org
Cc: dianders@...omium.org, jwerner@...omium.org, dtor@...omium.org,
hminas@...opsys.com, gregkh@...uxfoundation.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v2] usb: dwc2: host: use hrtimer for NAK retries
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: 38d2b5fb75c1 ("usb: dwc2: host: Don't retry NAKed transactions right away")
Signed-off-by: Terin Stock <terin@...instock.com>
---
drivers/usb/dwc2/hcd.h | 2 +-
drivers/usb/dwc2/hcd_queue.c | 19 ++++++++++++-------
2 files changed, 13 insertions(+), 8 deletions(-)
diff --git a/drivers/usb/dwc2/hcd.h b/drivers/usb/dwc2/hcd.h
index 5502a501f516..93483dc37801 100644
--- a/drivers/usb/dwc2/hcd.h
+++ b/drivers/usb/dwc2/hcd.h
@@ -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;
diff --git a/drivers/usb/dwc2/hcd_queue.c b/drivers/usb/dwc2/hcd_queue.c
index 301ced1618f8..60caf8e0b762 100644
--- a/drivers/usb/dwc2/hcd_queue.c
+++ b/drivers/usb/dwc2/hcd_queue.c
@@ -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);
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