USB: work around for EHCI with quirky periodic schedules

a quirky chipset needs periodic schedules to run for a minimum
time before they can be disabled again. This enforces the requirement
with a time stamp and a calculated delay

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/ehci-hcd.c

@@ -28,6 +28,7 @@
 #include <linux/errno.h>
 #include <linux/init.h>
 #include <linux/timer.h>
+#include <linux/ktime.h>
 #include <linux/list.h>
 #include <linux/interrupt.h>
 #include <linux/usb.h>
@@ -676,6 +677,7 @@ static int ehci_run (struct usb_hcd *hcd)
 	ehci_readl(ehci, &ehci->regs->command);	/* unblock posted writes */
 	msleep(5);
 	up_write(&ehci_cf_port_reset_rwsem);
+	ehci->last_periodic_enable = ktime_get_real();
 
 	temp = HC_VERSION(ehci_readl(ehci, &ehci->caps->hc_capbase));
 	ehci_info (ehci,

drivers/usb/host/ehci-pci.c

@@ -111,6 +111,10 @@ static int ehci_pci_setup(struct usb_hcd *hcd)
 	switch (pdev->vendor) {
 	case PCI_VENDOR_ID_INTEL:
 		ehci->need_io_watchdog = 0;
+		if (pdev->device == 0x27cc) {
+			ehci->broken_periodic = 1;
+			ehci_info(ehci, "using broken periodic workaround\n");
+		}
 		break;
 	case PCI_VENDOR_ID_TDI:
 		if (pdev->device == PCI_DEVICE_ID_TDI_EHCI) {

drivers/usb/host/ehci-sched.c

@@ -475,6 +475,8 @@ static int enable_periodic (struct ehci_hcd *ehci)
 	/* make sure ehci_work scans these */
 	ehci->next_uframe = ehci_readl(ehci, &ehci->regs->frame_index)
 		% (ehci->periodic_size << 3);
+	if (unlikely(ehci->broken_periodic))
+		ehci->last_periodic_enable = ktime_get_real();
 	return 0;
 }
 
@@ -486,6 +488,16 @@ static int disable_periodic (struct ehci_hcd *ehci)
 	if (--ehci->periodic_sched)
 		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...
 	 */

drivers/usb/host/ehci.h

@@ -118,6 +118,7 @@ struct ehci_hcd {			/* one per controller */
 	unsigned		stamp;
 	unsigned		random_frame;
 	unsigned long		next_statechange;
+	ktime_t			last_periodic_enable;
 	u32			command;
 
 	/* SILICON QUIRKS */
@@ -127,6 +128,7 @@ struct ehci_hcd {			/* one per controller */
 	unsigned		big_endian_desc:1;
 	unsigned		has_amcc_usb23:1;
 	unsigned		need_io_watchdog:1;
+	unsigned		broken_periodic:1;
 
 	/* required for usb32 quirk */
 	#define OHCI_CTRL_HCFS          (3 << 6)