In the past, the room_on_ring() check was implemented by walking all over
the ring, which is wasteful and complicated.
Count the number of free TRBs instead. The free TRBs number should be
updated when enqueue/dequeue pointer is updated, or upon the completion
of a set dequeue pointer command.
Signed-off-by: Andiry Xu <andiry.xu@xxxxxxx>
---
drivers/usb/host/xhci-mem.c | 6 +++
drivers/usb/host/xhci-ring.c | 72 +++++++++++++++--------------------------
drivers/usb/host/xhci.c | 1 +
drivers/usb/host/xhci.h | 1 +
4 files changed, 34 insertions(+), 46 deletions(-)
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index e794c87..98338a7 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -169,6 +169,12 @@ static struct xhci_ring *xhci_ring_alloc(struct xhci_hcd *xhci,
if (num_segs == 0)
return ring;
+ /* Each segment has a link TRB, and leave an extra TRB for SW
+ * accounting purpose
+ */
+
+ ring->num_trbs_free = num_segs * (TRBS_PER_SEGMENT - 1) - 1;
+
ring->first_seg = xhci_segment_alloc(xhci, flags);
if (!ring->first_seg)
goto fail;
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index e4b7f00..f914c2d 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -145,10 +145,16 @@ static void next_trb(struct xhci_hcd *xhci,
*/
static void inc_deq(struct xhci_hcd *xhci, struct xhci_ring *ring, bool consumer)
{
- union xhci_trb *next = ++(ring->dequeue);
+ union xhci_trb *next;
unsigned long long addr;
ring->deq_updates++;
+
+ /* If software is the producer, there is one more usable TRB */
+ if (!consumer && !last_trb(xhci, ring, ring->deq_seg, ring->dequeue))
+ ring->num_trbs_free++;
+ next = ++(ring->dequeue);
+
/* 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)
*/
@@ -192,6 +198,9 @@ static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring,
unsigned long long addr;
chain = le32_to_cpu(ring->enqueue->generic.field[3]) & TRB_CHAIN;
+ /* If software is the producer, there is one less usable TRB */
+ if (!consumer && !last_trb(xhci, ring, ring->enq_seg, ring->enqueue))
+ ring->num_trbs_free--;
next = ++(ring->enqueue);
ring->enq_updates++;
@@ -247,54 +256,14 @@ static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring,
/*
* 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;
- struct xhci_segment *cur_seg;
- unsigned int left_on_ring;
-
- /* If we are currently pointing to a link TRB, advance the
- * enqueue pointer before checking for space */
- while (last_trb(xhci, ring, enq_seg, enq)) {
- enq_seg = enq_seg->next;
- enq = enq_seg->trbs;
- }
-
- /* Check if ring is empty */
- if (enq == ring->dequeue) {
- /* Can't use link trbs */
- left_on_ring = TRBS_PER_SEGMENT - 1;
- for (cur_seg = enq_seg->next; cur_seg != enq_seg;
- cur_seg = cur_seg->next)
- left_on_ring += TRBS_PER_SEGMENT - 1;
-
- /* Always need one TRB free in the ring. */
- left_on_ring -= 1;
- if (num_trbs > left_on_ring) {
- xhci_warn(xhci, "Not enough room on ring; "
- "need %u TRBs, %u TRBs left\n",
- num_trbs, left_on_ring);
- return 0;
- }
+ if (ring->num_trbs_free >= num_trbs)
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;
+
+ return 0;
}
/* Ring the host controller doorbell after placing a command on the ring */
@@ -983,8 +952,19 @@ static void handle_set_deq_completion(struct xhci_hcd *xhci,
/* Update the ring's dequeue segment and dequeue pointer
* to reflect the new position.
*/
- ep_ring->deq_seg = dev->eps[ep_index].queued_deq_seg;
- ep_ring->dequeue = dev->eps[ep_index].queued_deq_ptr;
+ while (ep_ring->dequeue !=
+ dev->eps[ep_index].queued_deq_ptr) {
+ /* We have more usable TRBs */
+ ep_ring->num_trbs_free++;
+ ep_ring->dequeue++;
+ while (last_trb(xhci, ep_ring, ep_ring->deq_seg,
+ ep_ring->dequeue)) {
+ ep_ring->deq_seg =
+ ep_ring->deq_seg->next;
+ ep_ring->dequeue =
+ ep_ring->deq_seg->trbs;
+ }
+ }
} else {
xhci_warn(xhci, "Mismatch between completed Set TR Deq "
"Ptr command & xHCI internal state.\n");
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 1ff95a0..e70ddf2 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -721,6 +721,7 @@ static void xhci_clear_command_ring(struct xhci_hcd *xhci)
ring->enq_seg = ring->deq_seg;
ring->enqueue = ring->dequeue;
+ ring->num_trbs_free = ring->num_segs * (TRBS_PER_SEGMENT - 1) - 1;
/*
* Ring is now zeroed, so the HW should look for change of ownership
* when the cycle bit is set to 1.
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index a7f3d23..981dd83f 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1272,6 +1272,7 @@ struct xhci_ring {
u32 cycle_state;
unsigned int stream_id;
unsigned int num_segs;
+ unsigned int num_trbs_free;
bool last_td_was_short;
};
--
1.7.4.1
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