USB: ehci: qh/qtd cleanup comments (a082b5c7) · Commits · 戴 / test

drivers/usb/host/ehci-q.c

+40 −10

Original line number	Diff line number	Diff line
		@@ -336,11 +336,20 @@ qh_completions (struct ehci_hcd ehci, struct ehci_qh qh)
		/* always clean up qtds the hc de-activated */
		if ((token & QTD_STS_ACTIVE) == 0) {

		/* on STALL, error, and short reads this urb must
		* complete and all its qtds must be recycled.
		*/
		if ((token & QTD_STS_HALT) != 0) {
		stopped = 1;

		/* magic dummy for some short reads; qh won't advance.
		* that silicon quirk can kick in with this dummy too.
		*
		* other short reads won't stop the queue, including
		* control transfers (status stage handles that) or
		* most other single-qtd reads ... the queue stops if
		* URB_SHORT_NOT_OK was set so the driver submitting
		* the urbs could clean it up.
		*/
		} else if (IS_SHORT_READ (token)
		&& !(qtd->hw_alt_next
		@@ -354,18 +363,18 @@ qh_completions (struct ehci_hcd ehci, struct ehci_qh qh)
		&& HC_IS_RUNNING (ehci_to_hcd(ehci)->state))) {
		break;

		/* scan the whole queue for unlinks whenever it stops */
		} else {
		stopped = 1;

		if (unlikely (!HC_IS_RUNNING (ehci_to_hcd(ehci)->state)))
		/* cancel everything if we halt, suspend, etc */
		if (!HC_IS_RUNNING(ehci_to_hcd(ehci)->state))
		last_status = -ESHUTDOWN;

		/* ignore active urbs unless some previous qtd
		* for the urb faulted (including short read) or
		* its urb was canceled. we may patch qh or qtds.
		/* this qtd is active; skip it unless a previous qtd
		* for its urb faulted, or its urb was canceled.
		*/
		if (likely(last_status == -EINPROGRESS &&
		!urb->unlinked))
		else if (last_status == -EINPROGRESS && !urb->unlinked)
		continue;

		/* issue status after short control reads */
		@@ -375,7 +384,7 @@ qh_completions (struct ehci_hcd ehci, struct ehci_qh qh)
		continue;
		}

		/* token in overlay may be most current */
		/* qh unlinked; token in overlay may be most current */
		if (state == QH_STATE_IDLE
		&& cpu_to_hc32(ehci, qtd->qtd_dma)
		== qh->hw_current)
		@@ -402,11 +411,16 @@ halt:
		if (likely(last_status == -EINPROGRESS))
		last_status = qtd_status;

		/* if we're removing something not at the queue head,
		* patch the hardware queue pointer.
		*/
		if (stopped && qtd->qtd_list.prev != &qh->qtd_list) {
		last = list_entry (qtd->qtd_list.prev,
		struct ehci_qtd, qtd_list);
		last->hw_next = qtd->hw_next;
		}

		/* remove qtd; it's recycled after possible urb completion */
		list_del (&qtd->qtd_list);
		last = qtd;
		}
		@@ -431,7 +445,15 @@ halt:
		qh_refresh(ehci, qh);
		break;
		case QH_STATE_LINKED:
		/* should be rare for periodic transfers,
		/* We won't refresh a QH that's linked (after the HC
		* stopped the queue). That avoids a race:
		* - HC reads first part of QH;
		* - CPU updates that first part and the token;
		* - HC reads rest of that QH, including token
		* Result: HC gets an inconsistent image, and then
		* DMAs to/from the wrong memory (corrupting it).
		*
		* That should be rare for interrupt transfers,
		* except maybe high bandwidth ...
		*/
		if ((cpu_to_hc32(ehci, QH_SMASK)
		@@ -549,6 +571,12 @@ qh_urb_transaction (
		this_qtd_len = qtd_fill(ehci, qtd, buf, len, token, maxpacket);
		len -= this_qtd_len;
		buf += this_qtd_len;

		/*
		* short reads advance to a "magic" dummy instead of the next
		* qtd ... that forces the queue to stop, for manual cleanup.
		* (this will usually be overridden later.)
		*/
		if (is_input)
		qtd->hw_alt_next = ehci->async->hw_alt_next;

		@@ -568,8 +596,10 @@ qh_urb_transaction (
		list_add_tail (&qtd->qtd_list, head);
		}

		/* unless the bulk/interrupt caller wants a chance to clean
		* up after short reads, hc should advance qh past this urb
		/*
		* unless the caller requires manual cleanup after short reads,
		* have the alt_next mechanism keep the queue running after the
		* last data qtd (the only one, for control and most other cases).
		*/
		if (likely ((urb->transfer_flags & URB_SHORT_NOT_OK) == 0
		\|\| usb_pipecontrol (urb->pipe)))

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