On Wed, Jul 11, 2012 at 11:22 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> This patch (as1578) adds an hrtimer event to handle the death of an
> EHCI controller. When a controller dies, it doesn't necessarily stop
> running right away. The new event polls at 1-ms intervals to see when
> all activity has safely stopped. This replaces a busy-wait polling
> loop in the current code.
>
> Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
>
> ---
>
> drivers/usb/host/ehci-hcd.c | 20 ++++++++++----------
> drivers/usb/host/ehci-timer.c | 26 ++++++++++++++++++++++++++
> drivers/usb/host/ehci.h | 2 ++
> 3 files changed, 38 insertions(+), 10 deletions(-)
>
> Index: usb-3.4/drivers/usb/host/ehci.h
> ===================================================================
> --- usb-3.4.orig/drivers/usb/host/ehci.h
> +++ usb-3.4/drivers/usb/host/ehci.h
> @@ -81,6 +81,7 @@ enum ehci_rh_state {
> enum ehci_hrtimer_event {
> EHCI_HRTIMER_POLL_ASS, /* Poll for async schedule off */
> EHCI_HRTIMER_POLL_PSS, /* Poll for periodic schedule off */
> + EHCI_HRTIMER_POLL_DEAD, /* Wait for dead controller to stop */
> EHCI_HRTIMER_UNLINK_INTR, /* Wait for interrupt QH unlink */
> EHCI_HRTIMER_DISABLE_PERIODIC, /* Wait to disable periodic sched */
> EHCI_HRTIMER_DISABLE_ASYNC, /* Wait to disable async sched */
> @@ -97,6 +98,7 @@ struct ehci_hcd { /* one per controlle
>
> int PSS_poll_count;
> int ASS_poll_count;
> + int died_poll_count;
>
> /* glue to PCI and HCD framework */
> struct ehci_caps __iomem *caps;
> Index: usb-3.4/drivers/usb/host/ehci-hcd.c
> ===================================================================
> --- usb-3.4.orig/drivers/usb/host/ehci-hcd.c
> +++ usb-3.4/drivers/usb/host/ehci-hcd.c
> @@ -888,20 +888,20 @@ static irqreturn_t ehci_irq (struct usb_
> /* PCI errors [4.15.2.4] */
> if (unlikely ((status & STS_FATAL) != 0)) {
> ehci_err(ehci, "fatal error\n");
> - ehci->rh_state = EHCI_RH_STOPPING;
> dbg_cmd(ehci, "fatal", cmd);
> dbg_status(ehci, "fatal", status);
> - ehci_halt(ehci);
> dead:
> - ehci->enabled_hrtimer_events = 0;
> - hrtimer_try_to_cancel(&ehci->hrtimer);
> - ehci_reset(ehci);
> - ehci_writel(ehci, 0, &ehci->regs->configured_flag);
> usb_hc_died(hcd);
> - /* generic layer kills/unlinks all urbs, then
> - * uses ehci_stop to clean up the rest
> - */
> - bh = 1;
> +
> + /* Don't let the controller do anything more */
> + ehci->rh_state = EHCI_RH_STOPPING;
> + ehci->command &= ~(CMD_RUN | CMD_ASE | CMD_PSE);
> + ehci_writel(ehci, ehci->command, &ehci->regs->command);
> + ehci_writel(ehci, 0, &ehci->regs->intr_enable);
> + ehci_handle_controller_death(ehci);
> +
> + /* Handle completions when the controller stops */
> + bh = 0;
> }
>
> if (bh)
> Index: usb-3.4/drivers/usb/host/ehci-timer.c
> ===================================================================
> --- usb-3.4.orig/drivers/usb/host/ehci-timer.c
> +++ usb-3.4/drivers/usb/host/ehci-timer.c
> @@ -69,6 +69,7 @@ static void ehci_clear_command_bit(struc
> static unsigned event_delays_ns[] = {
> 1 * NSEC_PER_MSEC, /* EHCI_HRTIMER_POLL_ASS */
> 1 * NSEC_PER_MSEC, /* EHCI_HRTIMER_POLL_PSS */
> + 1 * NSEC_PER_MSEC, /* EHCI_HRTIMER_POLL_DEAD */
> 1125 * NSEC_PER_USEC, /* EHCI_HRTIMER_UNLINK_INTR */
> 10 * NSEC_PER_MSEC, /* EHCI_HRTIMER_DISABLE_PERIODIC */
> 15 * NSEC_PER_MSEC, /* EHCI_HRTIMER_DISABLE_ASYNC */
> @@ -193,6 +194,30 @@ static void ehci_disable_PSE(struct ehci
> }
>
>
> +/* Poll the STS_HALT status bit; see when a dead controller stops */
> +static void ehci_handle_controller_death(struct ehci_hcd *ehci)
> +{
> + if (!(ehci_readl(ehci, &ehci->regs->status) & STS_HALT)) {
If ehci_stop is runing when the EHCI_HRTIMER_POLL_DEAD event
is pending, there may be one race since ehci->enabled_hrtimer_events
is cleared in ehci_stop.
> +
> + /* Give up after a few milliseconds */
> + if (ehci->died_poll_count++ < 5) {
> + /* Try again later */
> + ehci_enable_event(ehci, EHCI_HRTIMER_POLL_DEAD, true);
> + return;
> + }
> + ehci_warn(ehci, "Waited too long for the controller to stop, giving up\n");
> + }
> +
> + /* Clean up the mess */
> + ehci->rh_state = EHCI_RH_HALTED;
> + ehci_writel(ehci, 0, &ehci->regs->configured_flag);
> + ehci_writel(ehci, 0, &ehci->regs->intr_enable);
> + ehci_work(ehci);
> +
> + /* Not in process context, so don't try to reset the controller */
> +}
> +
> +
> /* Handle unlinked interrupt QHs once they are gone from the hardware */
> static void ehci_handle_intr_unlinks(struct ehci_hcd *ehci)
> {
> @@ -233,6 +258,7 @@ static void ehci_handle_intr_unlinks(str
> static void (*event_handlers[])(struct ehci_hcd *) = {
> ehci_poll_ASS, /* EHCI_HRTIMER_POLL_ASS */
> ehci_poll_PSS, /* EHCI_HRTIMER_POLL_PSS */
> + ehci_handle_controller_death, /* EHCI_HRTIMER_POLL_DEAD */
> ehci_handle_intr_unlinks, /* EHCI_HRTIMER_UNLINK_INTR */
> ehci_disable_PSE, /* EHCI_HRTIMER_DISABLE_PERIODIC */
> ehci_disable_ASE, /* EHCI_HRTIMER_DISABLE_ASYNC */
>
>
> --
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Thanks,
--
Ming Lei
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