Commit 9aa09d2f authored by Karsten Wiese's avatar Karsten Wiese Committed by Greg Kroah-Hartman
Browse files

USB: EHCI: slow down ITD reuse 



Currently ITDs are immediately recycled whenever their URB completes.
However, EHCI hardware can sometimes remember some ITD state.  This
means that when the ITD is reused before end-of-frame it may sometimes
cause the hardware to reference bogus state.

This patch defers reusing such ITDs by moving them into a new ehci member
cached_itd_list. ITDs resting in cached_itd_list are moved back into their
stream's free_list once scan_periodic() detects that the active frame has
elapsed.

This makes the snd_usb_us122l driver (in kernel since .28) work right
when it's hooked up through EHCI.

[ dbrownell@users.sourceforge.net: comment fixups ]

Signed-off-by: default avatarKarsten Wiese <fzu@wemgehoertderstaat.de>
Tested-by: default avatarPhilippe Carriere <philippe-f.carriere@wanadoo.fr>
Tested-by: default avatarFederico Briata <federicobriata@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 9a6e184c

drivers/usb/host/ehci-hcd.c

+2 −0
Original line number Diff line number Diff line
@@ -485,6 +485,7 @@ static int ehci_init(struct usb_hcd *hcd) 
	 * periodic_size can shrink by USBCMD update if hcc_params allows.

	 */

	ehci->periodic_size = DEFAULT_I_TDPS;

	INIT_LIST_HEAD(&ehci->cached_itd_list);

	if ((retval = ehci_mem_init(ehci, GFP_KERNEL)) < 0)

		return retval;
@@ -497,6 +498,7 @@ static int ehci_init(struct usb_hcd *hcd) 


	ehci->reclaim = NULL;

	ehci->next_uframe = -1;

	ehci->clock_frame = -1;



	/*

	 * dedicate a qh for the async ring head, since we couldn't unlink

drivers/usb/host/ehci-mem.c

+1 −0
Original line number Diff line number Diff line
@@ -128,6 +128,7 @@ static inline void qh_put (struct ehci_qh *qh) 


static void ehci_mem_cleanup (struct ehci_hcd *ehci)

{

	free_cached_itd_list(ehci);

	if (ehci->async)

		qh_put (ehci->async);

	ehci->async = NULL;

drivers/usb/host/ehci-sched.c

+48 −8
Original line number Diff line number Diff line
@@ -1004,6 +1004,7 @@ iso_stream_put(struct ehci_hcd *ehci, struct ehci_iso_stream *stream) 


		is_in = (stream->bEndpointAddress & USB_DIR_IN) ? 0x10 : 0;

		stream->bEndpointAddress &= 0x0f;

		if (stream->ep)

			stream->ep->hcpriv = NULL;



		if (stream->rescheduled) {
@@ -1653,14 +1654,28 @@ itd_complete ( 
			(stream->bEndpointAddress & USB_DIR_IN) ? "in" : "out");

	}

	iso_stream_put (ehci, stream);

	/* OK to recycle this ITD now that its completion callback ran. */



done:

	usb_put_urb(urb);

	itd->urb = NULL;

	if (ehci->clock_frame != itd->frame || itd->index[7] != -1) {

		/* OK to recycle this ITD now. */

		itd->stream = NULL;

		list_move(&itd->itd_list, &stream->free_list);

		iso_stream_put(ehci, stream);



	} else {

		/* HW might remember this ITD, so we can't recycle it yet.

		 * Move it to a safe place until a new frame starts.

		 */

		list_move(&itd->itd_list, &ehci->cached_itd_list);

		if (stream->refcount == 2) {

			/* If iso_stream_put() were called here, stream

			 * would be freed.  Instead, just prevent reuse.

			 */

			stream->ep->hcpriv = NULL;

			stream->ep = NULL;

		}

	}

	return retval;

}
@@ -2101,6 +2116,20 @@ done: 


/*-------------------------------------------------------------------------*/



static void free_cached_itd_list(struct ehci_hcd *ehci)

{

	struct ehci_itd *itd, *n;



	list_for_each_entry_safe(itd, n, &ehci->cached_itd_list, itd_list) {

		struct ehci_iso_stream	*stream = itd->stream;

		itd->stream = NULL;

		list_move(&itd->itd_list, &stream->free_list);

		iso_stream_put(ehci, stream);

	}

}



/*-------------------------------------------------------------------------*/



static void

scan_periodic (struct ehci_hcd *ehci)

{
@@ -2115,10 +2144,17 @@ scan_periodic (struct ehci_hcd *ehci) 
	 * Touches as few pages as possible:  cache-friendly.

	 */

	now_uframe = ehci->next_uframe;

	if (HC_IS_RUNNING (ehci_to_hcd(ehci)->state))

	if (HC_IS_RUNNING(ehci_to_hcd(ehci)->state)) {

		clock = ehci_readl(ehci, &ehci->regs->frame_index);

	else

		clock_frame = (clock >> 3) % ehci->periodic_size;

	} else  {

		clock = now_uframe + mod - 1;

		clock_frame = -1;

	}

	if (ehci->clock_frame != clock_frame) {

		free_cached_itd_list(ehci);

		ehci->clock_frame = clock_frame;

	}

	clock %= mod;

	clock_frame = clock >> 3;
@@ -2277,6 +2313,10 @@ restart: 
			/* rescan the rest of this frame, then ... */

			clock = now;

			clock_frame = clock >> 3;

			if (ehci->clock_frame != clock_frame) {

				free_cached_itd_list(ehci);

				ehci->clock_frame = clock_frame;

			}

		} else {

			now_uframe++;

			now_uframe %= mod;

drivers/usb/host/ehci.h

+6 −0
Original line number Diff line number Diff line
@@ -87,6 +87,10 @@ struct ehci_hcd { /* one per controller */ 
	int			next_uframe;	/* scan periodic, start here */

	unsigned		periodic_sched;	/* periodic activity count */



	/* list of itds completed while clock_frame was still active */

	struct list_head	cached_itd_list;

	unsigned		clock_frame;



	/* per root hub port */

	unsigned long		reset_done [EHCI_MAX_ROOT_PORTS];
@@ -220,6 +224,8 @@ timer_action (struct ehci_hcd *ehci, enum ehci_timer_action action) 
	}

}



static void free_cached_itd_list(struct ehci_hcd *ehci);



/*-------------------------------------------------------------------------*/



#include <linux/usb/ehci_def.h>

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