From 4b39d891e4024baef1436ad2f97604998569bd06 Mon Sep 17 00:00:00 2001
From: David Brownell <david-b@pacbell.net>
Date: Fri, 7 Mar 2008 13:49:42 -0800
Subject: [PATCH] USB: fix ehci unlink regressions
The recent EHCI driver update to split the IAA watchdog timer out from
the other timers made several things work better, but not everything;
and it created a couple new issues in bugzilla. Ergo this patch:
- Handle a should-be-rare SMP race between the watchdog firing
and (very late) IAA interrupts;
- Remove a shouldn't-have-been-added WARN_ON() test;
- Guard against one observed OOPS;
- If this watchdog fires during clean HC shutdown, it should act
as a NOP instead of interfering with the shutdown sequence;
- Guard against silicon errata hypothesized by some vendors:
* IAA status latch broken, but IAAD cleared OK;
* IAAD wasn't cleared when IAA status got reported;
The WARN_ON is in bugzilla as 10168; the OOPS as 10078; these are
both regressions.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Tested-by: Gordon Farquharson <gordonfarquharson@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/usb/host/ehci-hcd.c | 62 +++++++++++++++++++++++++++----------
1 file changed, 46 insertions(+), 16 deletions(-)
diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index b8ad55aff8428..46ee7f4c09123 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -281,23 +281,44 @@ static void ehci_iaa_watchdog(unsigned long param)
{
struct ehci_hcd *ehci = (struct ehci_hcd *) param;
unsigned long flags;
- u32 status, cmd;
spin_lock_irqsave (&ehci->lock, flags);
- WARN_ON(!ehci->reclaim);
- status = ehci_readl(ehci, &ehci->regs->status);
- cmd = ehci_readl(ehci, &ehci->regs->command);
- ehci_dbg(ehci, "IAA watchdog: status %x cmd %x\n", status, cmd);
-
- /* lost IAA irqs wedge things badly; seen first with a vt8235 */
- if (ehci->reclaim) {
- if (status & STS_IAA) {
- ehci_vdbg (ehci, "lost IAA\n");
+ /* Lost IAA irqs wedge things badly; seen first with a vt8235.
+ * So we need this watchdog, but must protect it against both
+ * (a) SMP races against real IAA firing and retriggering, and
+ * (b) clean HC shutdown, when IAA watchdog was pending.
+ */
+ if (ehci->reclaim
+ && !timer_pending(&ehci->iaa_watchdog)
+ && HC_IS_RUNNING(ehci_to_hcd(ehci)->state)) {
+ u32 cmd, status;
+
+ /* If we get here, IAA is *REALLY* late. It's barely
+ * conceivable that the system is so busy that CMD_IAAD
+ * is still legitimately set, so let's be sure it's
+ * clear before we read STS_IAA. (The HC should clear
+ * CMD_IAAD when it sets STS_IAA.)
+ */
+ cmd = ehci_readl(ehci, &ehci->regs->command);
+ if (cmd & CMD_IAAD)
+ ehci_writel(ehci, cmd & ~CMD_IAAD,
+ &ehci->regs->command);
+
+ /* If IAA is set here it either legitimately triggered
+ * before we cleared IAAD above (but _way_ late, so we'll
+ * still count it as lost) ... or a silicon erratum:
+ * - VIA seems to set IAA without triggering the IRQ;
+ * - IAAD potentially cleared without setting IAA.
+ */
+ status = ehci_readl(ehci, &ehci->regs->status);
+ if ((status & STS_IAA) || !(cmd & CMD_IAAD)) {
COUNT (ehci->stats.lost_iaa);
ehci_writel(ehci, STS_IAA, &ehci->regs->status);
}
- ehci_writel(ehci, cmd & ~CMD_IAAD, &ehci->regs->command);
+
+ ehci_vdbg(ehci, "IAA watchdog: status %x cmd %x\n",
+ status, cmd);
end_unlink_async(ehci);
}
@@ -631,7 +652,7 @@ static int ehci_run (struct usb_hcd *hcd)
static irqreturn_t ehci_irq (struct usb_hcd *hcd)
{
struct ehci_hcd *ehci = hcd_to_ehci (hcd);
- u32 status, pcd_status = 0;
+ u32 status, pcd_status = 0, cmd;
int bh;
spin_lock (&ehci->lock);
@@ -652,7 +673,7 @@ static irqreturn_t ehci_irq (struct usb_hcd *hcd)
/* clear (just) interrupts */
ehci_writel(ehci, status, &ehci->regs->status);
- ehci_readl(ehci, &ehci->regs->command); /* unblock posted write */
+ cmd = ehci_readl(ehci, &ehci->regs->command);
bh = 0;
#ifdef EHCI_VERBOSE_DEBUG
@@ -673,8 +694,17 @@ static irqreturn_t ehci_irq (struct usb_hcd *hcd)
/* complete the unlinking of some qh [4.15.2.3] */
if (status & STS_IAA) {
- COUNT (ehci->stats.reclaim);
- end_unlink_async(ehci);
+ /* guard against (alleged) silicon errata */
+ if (cmd & CMD_IAAD) {
+ ehci_writel(ehci, cmd & ~CMD_IAAD,
+ &ehci->regs->command);
+ ehci_dbg(ehci, "IAA with IAAD still set?\n");
+ }
+ if (ehci->reclaim) {
+ COUNT(ehci->stats.reclaim);
+ end_unlink_async(ehci);
+ } else
+ ehci_dbg(ehci, "IAA with nothing to reclaim?\n");
}
/* remote wakeup [4.3.1] */
@@ -781,7 +811,7 @@ static int ehci_urb_enqueue (
static void unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
{
/* failfast */
- if (!HC_IS_RUNNING(ehci_to_hcd(ehci)->state))
+ if (!HC_IS_RUNNING(ehci_to_hcd(ehci)->state) && ehci->reclaim)
end_unlink_async(ehci);
/* if it's not linked then there's nothing to do */
--
2.39.5