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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: 38d2b5fb75
("usb: dwc2: host: Don't retry NAKed transactions right away")
Cc: <stable@vger.kernel.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Terin Stock <terin@terinstock.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
This commit is contained in:
parent
47b6f8bf87
commit
6ed30a7d8e
2 changed files with 13 additions and 8 deletions
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@ -366,7 +366,7 @@ struct dwc2_qh {
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u32 desc_list_sz;
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u32 *n_bytes;
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struct timer_list unreserve_timer;
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struct timer_list wait_timer;
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struct hrtimer wait_timer;
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struct dwc2_tt *dwc_tt;
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int ttport;
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unsigned tt_buffer_dirty:1;
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@ -59,7 +59,7 @@
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#define DWC2_UNRESERVE_DELAY (msecs_to_jiffies(5))
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/* If we get a NAK, wait this long before retrying */
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#define DWC2_RETRY_WAIT_DELAY (msecs_to_jiffies(1))
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#define DWC2_RETRY_WAIT_DELAY 1*1E6L
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/**
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* dwc2_periodic_channel_available() - Checks that a channel is available for a
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@ -1464,10 +1464,12 @@ static void dwc2_deschedule_periodic(struct dwc2_hsotg *hsotg,
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* qh back to the "inactive" list, then queues transactions.
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*
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* @t: Pointer to wait_timer in a qh.
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*
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* Return: HRTIMER_NORESTART to not automatically restart this timer.
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*/
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static void dwc2_wait_timer_fn(struct timer_list *t)
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static enum hrtimer_restart dwc2_wait_timer_fn(struct hrtimer *t)
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{
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struct dwc2_qh *qh = from_timer(qh, t, wait_timer);
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struct dwc2_qh *qh = container_of(t, struct dwc2_qh, wait_timer);
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struct dwc2_hsotg *hsotg = qh->hsotg;
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unsigned long flags;
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@ -1491,6 +1493,7 @@ static void dwc2_wait_timer_fn(struct timer_list *t)
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}
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spin_unlock_irqrestore(&hsotg->lock, flags);
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return HRTIMER_NORESTART;
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}
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/**
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@ -1521,7 +1524,8 @@ static void dwc2_qh_init(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh,
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/* Initialize QH */
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qh->hsotg = hsotg;
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timer_setup(&qh->unreserve_timer, dwc2_unreserve_timer_fn, 0);
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timer_setup(&qh->wait_timer, dwc2_wait_timer_fn, 0);
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hrtimer_init(&qh->wait_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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qh->wait_timer.function = &dwc2_wait_timer_fn;
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qh->ep_type = ep_type;
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qh->ep_is_in = ep_is_in;
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@ -1690,7 +1694,7 @@ void dwc2_hcd_qh_free(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
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* won't do anything anyway, but we want it to finish before we free
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* memory.
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*/
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del_timer_sync(&qh->wait_timer);
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hrtimer_cancel(&qh->wait_timer);
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dwc2_host_put_tt_info(hsotg, qh->dwc_tt);
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@ -1716,6 +1720,7 @@ int dwc2_hcd_qh_add(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
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{
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int status;
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u32 intr_mask;
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ktime_t delay;
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if (dbg_qh(qh))
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dev_vdbg(hsotg->dev, "%s()\n", __func__);
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@ -1734,8 +1739,8 @@ int dwc2_hcd_qh_add(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
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list_add_tail(&qh->qh_list_entry,
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&hsotg->non_periodic_sched_waiting);
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qh->wait_timer_cancel = false;
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mod_timer(&qh->wait_timer,
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jiffies + DWC2_RETRY_WAIT_DELAY + 1);
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delay = ktime_set(0, DWC2_RETRY_WAIT_DELAY);
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hrtimer_start(&qh->wait_timer, delay, HRTIMER_MODE_REL);
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} else {
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list_add_tail(&qh->qh_list_entry,
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&hsotg->non_periodic_sched_inactive);
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