From 3ca9aebac2ebb8f56d2d097636b8c568320a9f87 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Wed, 11 Jul 2012 11:22:05 -0400 Subject: USB: EHCI: use hrtimer for the periodic schedule This patch (as1573) adds hrtimer support for managing ehci-hcd's periodic schedule. There are two issues to deal with. First, the schedule's state (on or off) must not be changed until the hardware status has caught up with the current command. This is handled by an hrtimer event that polls at 1-ms intervals to see when the Periodic Schedule Status (PSS) flag matches the Periodic Schedule Enable (PSE) value. Second, the schedule should not be turned off as soon as it becomes empty. Turning the schedule on and off takes time, so we want to wait until the schedule has been empty for a suitable period before turning it off. This is handled by an hrtimer event that gets set to expire 10 ms after the periodic schedule becomes empty. The existing code polls (for up to 1125 us and with interrupts disabled!) to check the status, and doesn't implement a delay before turning off the schedule. Furthermore, if the polling fails then the driver decides that the controller has died. This has caused problems for several people; some controllers can take 10 ms or more to turn off their periodic schedules. This patch fixes these issues. It also makes the "broken_periodic" workaround unnecessary; there is no longer any danger of turning off the periodic schedule after it has been on for less than 1 ms. Signed-off-by: Alan Stern Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/ehci-sched.c | 69 ++++++++++--------------------------------- 1 file changed, 15 insertions(+), 54 deletions(-) (limited to 'drivers/usb/host/ehci-sched.c') diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c index 3429b8a33c58..f5c15880c65a 100644 --- a/drivers/usb/host/ehci-sched.c +++ b/drivers/usb/host/ehci-sched.c @@ -481,67 +481,26 @@ static int tt_no_collision ( static int enable_periodic (struct ehci_hcd *ehci) { - int status; - - if (ehci->periodic_sched++) + if (ehci->periodic_count++) return 0; - /* did clearing PSE did take effect yet? - * takes effect only at frame boundaries... - */ - status = handshake_on_error_set_halt(ehci, &ehci->regs->status, - STS_PSS, 0, 9 * 125); - if (status) { - usb_hc_died(ehci_to_hcd(ehci)); - return status; - } - - ehci->command |= CMD_PSE; - ehci_writel(ehci, ehci->command, &ehci->regs->command); - /* posted write ... PSS happens later */ + /* Stop waiting to turn off the periodic schedule */ + ehci->enabled_hrtimer_events &= ~BIT(EHCI_HRTIMER_DISABLE_PERIODIC); - /* make sure ehci_work scans these */ - ehci->next_uframe = ehci_read_frame_index(ehci) - % (ehci->periodic_size << 3); - if (unlikely(ehci->broken_periodic)) - ehci->last_periodic_enable = ktime_get_real(); + /* Don't start the schedule until PSS is 0 */ + ehci_poll_PSS(ehci); return 0; } static int disable_periodic (struct ehci_hcd *ehci) { - int status; - - if (--ehci->periodic_sched) + if (--ehci->periodic_count) return 0; - if (unlikely(ehci->broken_periodic)) { - /* delay experimentally determined */ - ktime_t safe = ktime_add_us(ehci->last_periodic_enable, 1000); - ktime_t now = ktime_get_real(); - s64 delay = ktime_us_delta(safe, now); - - if (unlikely(delay > 0)) - udelay(delay); - } - - /* did setting PSE not take effect yet? - * takes effect only at frame boundaries... - */ - status = handshake_on_error_set_halt(ehci, &ehci->regs->status, - STS_PSS, STS_PSS, 9 * 125); - if (status) { - usb_hc_died(ehci_to_hcd(ehci)); - return status; - } - - ehci->command &= ~CMD_PSE; - ehci_writel(ehci, ehci->command, &ehci->regs->command); - /* posted write ... */ - - free_cached_lists(ehci); + ehci->next_uframe = -1; /* the periodic schedule is empty */ - ehci->next_uframe = -1; + /* Don't turn off the schedule until PSS is 1 */ + ehci_poll_PSS(ehci); return 0; } @@ -650,8 +609,7 @@ static int qh_unlink_periodic(struct ehci_hcd *ehci, struct ehci_qh *qh) qh->qh_state = QH_STATE_UNLINK; qh->qh_next.ptr = NULL; - /* maybe turn off periodic schedule */ - return disable_periodic(ehci); + return 0; } static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh) @@ -706,6 +664,9 @@ static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh) ehci_err(ehci, "can't reschedule qh %p, err %d\n", qh, rc); } + + /* maybe turn off periodic schedule */ + disable_periodic(ehci); } /*-------------------------------------------------------------------------*/ @@ -2447,7 +2408,7 @@ restart: /* assume completion callbacks modify the queue */ if (unlikely (modified)) { - if (likely(ehci->periodic_sched > 0)) + if (likely(ehci->periodic_count > 0)) goto restart; /* short-circuit this scan */ now_uframe = clock; @@ -2476,7 +2437,7 @@ restart: unsigned now; if (ehci->rh_state < EHCI_RH_RUNNING - || ehci->periodic_sched == 0) + || ehci->periodic_count == 0) break; ehci->next_uframe = now_uframe; now = ehci_read_frame_index(ehci) & (mod - 1); -- cgit v1.2.3