USB: xhci: No-op command queueing and irq handler.

xHCI host controllers can optionally implement a no-op test.  This
simple test ensures the OS has correctly setup all basic data structures
and can correctly respond to interrupts from the host controller
hardware.

There are two rings exercised by the no-op test:  the command ring, and
the event ring.

The host controller driver writes a no-op command TRB to the command
ring, and rings the doorbell for the command ring (the first entry in
the doorbell array).  The hardware receives this event, places a command
completion event on the event ring, and fires an interrupt.

The host controller driver sees the interrupt, and checks the event ring
for TRBs it can process, and sees the command completion event.  (See
the rules in xhci-ring.c for who "owns" a TRB.  This is a simplified set
of rules, and may not contain all the details that are in the xHCI 0.95
spec.)

A timer fires every 60 seconds to debug the state of the hardware and
command and event rings.  This timer only runs if
CONFIG_USB_XHCI_HCD_DEBUGGING is 'y'.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 367 insertions, 0 deletions

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
new file mode 100644
index 000000000000..c7e3c7142b9d
--- /dev/null
+++ b/drivers/usb/host/xhci-ring.c
@@ -0,0 +1,367 @@
+/*
+ * xHCI host controller driver
+ *
+ * Copyright (C) 2008 Intel Corp.
+ *
+ * Author: Sarah Sharp
+ * Some code borrowed from the Linux EHCI driver.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/*
+ * Ring initialization rules:
+ * 1. Each segment is initialized to zero, except for link TRBs.
+ * 2. Ring cycle state = 0.  This represents Producer Cycle State (PCS) or
+ *    Consumer Cycle State (CCS), depending on ring function.
+ * 3. Enqueue pointer = dequeue pointer = address of first TRB in the segment.
+ *
+ * Ring behavior rules:
+ * 1. A ring is empty if enqueue == dequeue.  This means there will always be at
+ *    least one free TRB in the ring.  This is useful if you want to turn that
+ *    into a link TRB and expand the ring.
+ * 2. When incrementing an enqueue or dequeue pointer, if the next TRB is a
+ *    link TRB, then load the pointer with the address in the link TRB.  If the
+ *    link TRB had its toggle bit set, you may need to update the ring cycle
+ *    state (see cycle bit rules).  You may have to do this multiple times
+ *    until you reach a non-link TRB.
+ * 3. A ring is full if enqueue++ (for the definition of increment above)
+ *    equals the dequeue pointer.
+ *
+ * Cycle bit rules:
+ * 1. When a consumer increments a dequeue pointer and encounters a toggle bit
+ *    in a link TRB, it must toggle the ring cycle state.
+ * 2. When a producer increments an enqueue pointer and encounters a toggle bit
+ *    in a link TRB, it must toggle the ring cycle state.
+ *
+ * Producer rules:
+ * 1. Check if ring is full before you enqueue.
+ * 2. Write the ring cycle state to the cycle bit in the TRB you're enqueuing.
+ *    Update enqueue pointer between each write (which may update the ring
+ *    cycle state).
+ * 3. Notify consumer.  If SW is producer, it rings the doorbell for command
+ *    and endpoint rings.  If HC is the producer for the event ring,
+ *    and it generates an interrupt according to interrupt modulation rules.
+ *
+ * Consumer rules:
+ * 1. Check if TRB belongs to you.  If the cycle bit == your ring cycle state,
+ *    the TRB is owned by the consumer.
+ * 2. Update dequeue pointer (which may update the ring cycle state) and
+ *    continue processing TRBs until you reach a TRB which is not owned by you.
+ * 3. Notify the producer.  SW is the consumer for the event ring, and it
+ *   updates event ring dequeue pointer.  HC is the consumer for the command and
+ *   endpoint rings; it generates events on the event ring for these.
+ */
+
+#include "xhci.h"
+
+/*
+ * Returns zero if the TRB isn't in this segment, otherwise it returns the DMA
+ * address of the TRB.
+ */
+dma_addr_t trb_virt_to_dma(struct xhci_segment *seg,
+		union xhci_trb *trb)
+{
+	unsigned int offset;
+
+	if (!seg || !trb || (void *) trb < (void *) seg->trbs)
+		return 0;
+	/* offset in bytes, since these are byte-addressable */
+	offset = (unsigned int) trb - (unsigned int) seg->trbs;
+	/* SEGMENT_SIZE in bytes, trbs are 16-byte aligned */
+	if (offset > SEGMENT_SIZE || (offset % sizeof(*trb)) != 0)
+		return 0;
+	return seg->dma + offset;
+}
+
+/* Does this link TRB point to the first segment in a ring,
+ * or was the previous TRB the last TRB on the last segment in the ERST?
+ */
+static inline bool last_trb_on_last_seg(struct xhci_hcd *xhci, struct xhci_ring *ring,
+		struct xhci_segment *seg, union xhci_trb *trb)
+{
+	if (ring == xhci->event_ring)
+		return (trb == &seg->trbs[TRBS_PER_SEGMENT]) &&
+			(seg->next == xhci->event_ring->first_seg);
+	else
+		return trb->link.control & LINK_TOGGLE;
+}
+
+/* Is this TRB a link TRB or was the last TRB the last TRB in this event ring
+ * segment?  I.e. would the updated event TRB pointer step off the end of the
+ * event seg?
+ */
+static inline int last_trb(struct xhci_hcd *xhci, struct xhci_ring *ring,
+		struct xhci_segment *seg, union xhci_trb *trb)
+{
+	if (ring == xhci->event_ring)
+		return trb == &seg->trbs[TRBS_PER_SEGMENT];
+	else
+		return (trb->link.control & TRB_TYPE_BITMASK) == TRB_TYPE(TRB_LINK);
+}
+
+/*
+ * See Cycle bit rules. SW is the consumer for the event ring only.
+ * Don't make a ring full of link TRBs.  That would be dumb and this would loop.
+ */
+static void inc_deq(struct xhci_hcd *xhci, struct xhci_ring *ring, bool consumer)
+{
+	union xhci_trb *next = ++(ring->dequeue);
+
+	ring->deq_updates++;
+	/* Update the dequeue pointer further if that was a link TRB or we're at
+	 * the end of an event ring segment (which doesn't have link TRBS)
+	 */
+	while (last_trb(xhci, ring, ring->deq_seg, next)) {
+		if (consumer && last_trb_on_last_seg(xhci, ring, ring->deq_seg, next)) {
+			ring->cycle_state = (ring->cycle_state ? 0 : 1);
+			if (!in_interrupt())
+				xhci_dbg(xhci, "Toggle cycle state for ring 0x%x = %i\n",
+						(unsigned int) ring,
+						(unsigned int) ring->cycle_state);
+		}
+		ring->deq_seg = ring->deq_seg->next;
+		ring->dequeue = ring->deq_seg->trbs;
+		next = ring->dequeue;
+	}
+}
+
+/*
+ * See Cycle bit rules. SW is the consumer for the event ring only.
+ * Don't make a ring full of link TRBs.  That would be dumb and this would loop.
+ *
+ * If we've just enqueued a TRB that is in the middle of a TD (meaning the
+ * chain bit is set), then set the chain bit in all the following link TRBs.
+ * If we've enqueued the last TRB in a TD, make sure the following link TRBs
+ * have their chain bit cleared (so that each Link TRB is a separate TD).
+ *
+ * Section 6.4.4.1 of the 0.95 spec says link TRBs cannot have the chain bit
+ * set, but other sections talk about dealing with the chain bit set.
+ * Assume section 6.4.4.1 is wrong, and the chain bit can be set in a Link TRB.
+ */
+static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring, bool consumer)
+{
+	u32 chain;
+	union xhci_trb *next;
+
+	chain = ring->enqueue->generic.field[3] & TRB_CHAIN;
+	next = ++(ring->enqueue);
+
+	ring->enq_updates++;
+	/* Update the dequeue pointer further if that was a link TRB or we're at
+	 * the end of an event ring segment (which doesn't have link TRBS)
+	 */
+	while (last_trb(xhci, ring, ring->enq_seg, next)) {
+		if (!consumer) {
+			if (ring != xhci->event_ring) {
+				/* Give this link TRB to the hardware */
+				if (next->link.control & TRB_CYCLE)
+					next->link.control &= (u32) ~TRB_CYCLE;
+				else
+					next->link.control |= (u32) TRB_CYCLE;
+				next->link.control &= TRB_CHAIN;
+				next->link.control |= chain;
+			}
+			/* Toggle the cycle bit after the last ring segment. */
+			if (last_trb_on_last_seg(xhci, ring, ring->enq_seg, next)) {
+				ring->cycle_state = (ring->cycle_state ? 0 : 1);
+				if (!in_interrupt())
+					xhci_dbg(xhci, "Toggle cycle state for ring 0x%x = %i\n",
+							(unsigned int) ring,
+							(unsigned int) ring->cycle_state);
+			}
+		}
+		ring->enq_seg = ring->enq_seg->next;
+		ring->enqueue = ring->enq_seg->trbs;
+		next = ring->enqueue;
+	}
+}
+
+/*
+ * Check to see if there's room to enqueue num_trbs on the ring.  See rules
+ * above.
+ * FIXME: this would be simpler and faster if we just kept track of the number
+ * of free TRBs in a ring.
+ */
+static int room_on_ring(struct xhci_hcd *xhci, struct xhci_ring *ring,
+		unsigned int num_trbs)
+{
+	int i;
+	union xhci_trb *enq = ring->enqueue;
+	struct xhci_segment *enq_seg = ring->enq_seg;
+
+	/* Check if ring is empty */
+	if (enq == ring->dequeue)
+		return 1;
+	/* Make sure there's an extra empty TRB available */
+	for (i = 0; i <= num_trbs; ++i) {
+		if (enq == ring->dequeue)
+			return 0;
+		enq++;
+		while (last_trb(xhci, ring, enq_seg, enq)) {
+			enq_seg = enq_seg->next;
+			enq = enq_seg->trbs;
+		}
+	}
+	return 1;
+}
+
+void set_hc_event_deq(struct xhci_hcd *xhci)
+{
+	u32 temp;
+	dma_addr_t deq;
+
+	deq = trb_virt_to_dma(xhci->event_ring->deq_seg,
+			xhci->event_ring->dequeue);
+	if (deq == 0 && !in_interrupt())
+		xhci_warn(xhci, "WARN something wrong with SW event ring "
+				"dequeue ptr.\n");
+	/* Update HC event ring dequeue pointer */
+	temp = xhci_readl(xhci, &xhci->ir_set->erst_dequeue[0]);
+	temp &= ERST_PTR_MASK;
+	if (!in_interrupt())
+		xhci_dbg(xhci, "// Write event ring dequeue pointer\n");
+	xhci_writel(xhci, 0, &xhci->ir_set->erst_dequeue[1]);
+	xhci_writel(xhci, (deq & ~ERST_PTR_MASK) | temp,
+			&xhci->ir_set->erst_dequeue[0]);
+}
+
+/* Ring the host controller doorbell after placing a command on the ring */
+void ring_cmd_db(struct xhci_hcd *xhci)
+{
+	u32 temp;
+
+	xhci_dbg(xhci, "// Ding dong!\n");
+	temp = xhci_readl(xhci, &xhci->dba->doorbell[0]) & DB_MASK;
+	xhci_writel(xhci, temp | DB_TARGET_HOST, &xhci->dba->doorbell[0]);
+	/* Flush PCI posted writes */
+	xhci_readl(xhci, &xhci->dba->doorbell[0]);
+}
+
+static void handle_cmd_completion(struct xhci_hcd *xhci,
+		struct xhci_event_cmd *event)
+{
+	u64 cmd_dma;
+	dma_addr_t cmd_dequeue_dma;
+
+	/* Check completion code */
+	if (GET_COMP_CODE(event->status) != COMP_SUCCESS)
+		xhci_dbg(xhci, "WARN: unsuccessful no-op command\n");
+
+	cmd_dma = (((u64) event->cmd_trb[1]) << 32) + event->cmd_trb[0];
+	cmd_dequeue_dma = trb_virt_to_dma(xhci->cmd_ring->deq_seg,
+			xhci->cmd_ring->dequeue);
+	/* Is the command ring deq ptr out of sync with the deq seg ptr? */
+	if (cmd_dequeue_dma == 0) {
+		xhci->error_bitmask |= 1 << 4;
+		return;
+	}
+	/* Does the DMA address match our internal dequeue pointer address? */
+	if (cmd_dma != (u64) cmd_dequeue_dma) {
+		xhci->error_bitmask |= 1 << 5;
+		return;
+	}
+	switch (xhci->cmd_ring->dequeue->generic.field[3] & TRB_TYPE_BITMASK) {
+	case TRB_TYPE(TRB_CMD_NOOP):
+		++xhci->noops_handled;
+		break;
+	default:
+		/* Skip over unknown commands on the event ring */
+		xhci->error_bitmask |= 1 << 6;
+		break;
+	}
+	inc_deq(xhci, xhci->cmd_ring, false);
+}
+
+void handle_event(struct xhci_hcd *xhci)
+{
+	union xhci_trb *event;
+
+	if (!xhci->event_ring || !xhci->event_ring->dequeue) {
+		xhci->error_bitmask |= 1 << 1;
+		return;
+	}
+
+	event = xhci->event_ring->dequeue;
+	/* Does the HC or OS own the TRB? */
+	if ((event->event_cmd.flags & TRB_CYCLE) !=
+			xhci->event_ring->cycle_state) {
+		xhci->error_bitmask |= 1 << 2;
+		return;
+	}
+
+	/* FIXME: Only handles command completion events. */
+	switch ((event->event_cmd.flags & TRB_TYPE_BITMASK)) {
+	case TRB_TYPE(TRB_COMPLETION):
+		handle_cmd_completion(xhci, &event->event_cmd);
+		break;
+	default:
+		xhci->error_bitmask |= 1 << 3;
+	}
+
+	/* Update SW and HC event ring dequeue pointer */
+	inc_deq(xhci, xhci->event_ring, true);
+	set_hc_event_deq(xhci);
+	/* Are there more items on the event ring? */
+	handle_event(xhci);
+}
+
+/*
+ * Generic function for queueing a TRB on a ring.
+ * The caller must have checked to make sure there's room on the ring.
+ */
+static void queue_trb(struct xhci_hcd *xhci, struct xhci_ring *ring,
+		bool consumer,
+		u32 field1, u32 field2, u32 field3, u32 field4)
+{
+	struct xhci_generic_trb *trb;
+
+	trb = &ring->enqueue->generic;
+	trb->field[0] = field1;
+	trb->field[1] = field2;
+	trb->field[2] = field3;
+	trb->field[3] = field4;
+	inc_enq(xhci, ring, consumer);
+}
+
+/* Generic function for queueing a command TRB on the command ring */
+static int queue_command(struct xhci_hcd *xhci, u32 field1, u32 field2, u32 field3, u32 field4)
+{
+	if (!room_on_ring(xhci, xhci->cmd_ring, 1)) {
+		if (!in_interrupt())
+			xhci_err(xhci, "ERR: No room for command on command ring\n");
+		return -ENOMEM;
+	}
+	queue_trb(xhci, xhci->cmd_ring, false, field1, field2, field3,
+			field4 | xhci->cmd_ring->cycle_state);
+	return 0;
+}
+
+/* Queue a no-op command on the command ring */
+static int queue_cmd_noop(struct xhci_hcd *xhci)
+{
+	return queue_command(xhci, 0, 0, 0, TRB_TYPE(TRB_CMD_NOOP));
+}
+
+/*
+ * Place a no-op command on the command ring to test the command and
+ * event ring.
+ */
+void *setup_one_noop(struct xhci_hcd *xhci)
+{
+	if (queue_cmd_noop(xhci) < 0)
+		return NULL;
+	xhci->noops_submitted++;
+	return ring_cmd_db;
+}