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 <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index 070be83..da2e0ab 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -79,6 +79,8 @@
* ehci-timer.c) in parallel with this list.
*/
enum ehci_hrtimer_event {
+ EHCI_HRTIMER_POLL_PSS, /* Poll for periodic schedule off */
+ EHCI_HRTIMER_DISABLE_PERIODIC, /* Wait to disable periodic sched */
EHCI_HRTIMER_NUM_EVENTS /* Must come last */
};
#define EHCI_HRTIMER_NO_EVENT 99
@@ -90,6 +92,8 @@
ktime_t hr_timeouts[EHCI_HRTIMER_NUM_EVENTS];
struct hrtimer hrtimer;
+ int PSS_poll_count;
+
/* glue to PCI and HCD framework */
struct ehci_caps __iomem *caps;
struct ehci_regs __iomem *regs;
@@ -116,7 +120,7 @@
union ehci_shadow *pshadow; /* mirror hw periodic table */
int next_uframe; /* scan periodic, start here */
- unsigned periodic_sched; /* periodic activity count */
+ unsigned periodic_count; /* periodic activity count */
unsigned uframe_periodic_max; /* max periodic time per uframe */
@@ -165,7 +169,6 @@
unsigned big_endian_capbase:1;
unsigned has_amcc_usb23:1;
unsigned need_io_watchdog:1;
- unsigned broken_periodic:1;
unsigned amd_pll_fix:1;
unsigned fs_i_thresh:1; /* Intel iso scheduling */
unsigned use_dummy_qh:1; /* AMD Frame List table quirk*/