This patch (as1541) corrects a small mistake in ehci-hcd. The IAAD
(Interrupt on Async Advance Doorbell) bit in the USBCMD register is
designed, as its name says, to act as a "doorbell". That is, the
driver activates the bit by setting it to 1, and the hardware
deactivates it later by setting it back to 0. The driver cannot clear
the bit by writing a 0 to it; such writes are simply ignored.
Therefore there is no reason for ehci-hcd to try to clear the bit.
The patch removes the two instances where such attempts occur.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/host/ehci-hcd.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
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
@@ -417,9 +417,6 @@ static void ehci_iaa_watchdog(unsigned l
* 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
@@ -889,11 +886,8 @@ static irqreturn_t ehci_irq (struct usb_
/* complete the unlinking of some qh [4.15.2.3] */
if (status & STS_IAA) {
/* guard against (alleged) silicon errata */
- if (cmd & CMD_IAAD) {
- ehci_writel(ehci, cmd & ~CMD_IAAD,
- &ehci->regs->command);
+ if (cmd & CMD_IAAD)
ehci_dbg(ehci, "IAA with IAAD still set?\n");
- }
if (ehci->reclaim) {
COUNT(ehci->stats.reclaim);
end_unlink_async(ehci);
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
