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Commit d98b1937 authored by Ralph Campbell's avatar Ralph Campbell Committed by Roland Dreier
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IB/ipath: Use PIO buffer for RC ACKs 



This reduces the latency for RC ACKs when a PIO buffer is available.

Signed-off-by: default avatarRalph Campbell <ralph.campbell@qlogic.com>
Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
parent c4b4d16e

drivers/infiniband/hw/ipath/ipath_rc.c

+39 −18
Original line number Diff line number Diff line
@@ -31,6 +31,8 @@ 
 * SOFTWARE.

 */



#include <linux/io.h>



#include "ipath_verbs.h"

#include "ipath_kernel.h"
@@ -585,19 +587,39 @@ bail: 
static void send_rc_ack(struct ipath_qp *qp)

{

	struct ipath_ibdev *dev = to_idev(qp->ibqp.device);

	struct ipath_devdata *dd;

	u16 lrh0;

	u32 bth0;

	u32 hwords;

	u32 __iomem *piobuf;

	struct ipath_ib_header hdr;

	struct ipath_other_headers *ohdr;

	unsigned long flags;



	spin_lock_irqsave(&qp->s_lock, flags);



	/* Don't send ACK or NAK if a RDMA read or atomic is pending. */

	if (qp->r_head_ack_queue != qp->s_tail_ack_queue ||

	    (qp->s_flags & IPATH_S_ACK_PENDING) ||

	    qp->s_ack_state != OP(ACKNOWLEDGE))

		goto queue_ack;



	spin_unlock_irqrestore(&qp->s_lock, flags);



	dd = dev->dd;

	piobuf = ipath_getpiobuf(dd, 0, NULL);

	if (!piobuf) {

		/*

		 * We are out of PIO buffers at the moment.

		 * Pass responsibility for sending the ACK to the

		 * send tasklet so that when a PIO buffer becomes

		 * available, the ACK is sent ahead of other outgoing

		 * packets.

		 */

		spin_lock_irqsave(&qp->s_lock, flags);

		goto queue_ack;

	}



	/* Construct the header. */

	ohdr = &hdr.u.oth;

	lrh0 = IPATH_LRH_BTH;
@@ -611,7 +633,7 @@ static void send_rc_ack(struct ipath_qp *qp) 
		lrh0 = IPATH_LRH_GRH;

	}

	/* read pkey_index w/o lock (its atomic) */

	bth0 = ipath_get_pkey(dev->dd, qp->s_pkey_index) |

	bth0 = ipath_get_pkey(dd, qp->s_pkey_index) |

		(OP(ACKNOWLEDGE) << 24) | (1 << 22);

	if (qp->r_nak_state)

		ohdr->u.aeth = cpu_to_be32((qp->r_msn & IPATH_MSN_MASK) |
@@ -623,30 +645,29 @@ static void send_rc_ack(struct ipath_qp *qp) 
	hdr.lrh[0] = cpu_to_be16(lrh0);

	hdr.lrh[1] = cpu_to_be16(qp->remote_ah_attr.dlid);

	hdr.lrh[2] = cpu_to_be16(hwords + SIZE_OF_CRC);

	hdr.lrh[3] = cpu_to_be16(dev->dd->ipath_lid);

	hdr.lrh[3] = cpu_to_be16(dd->ipath_lid);

	ohdr->bth[0] = cpu_to_be32(bth0);

	ohdr->bth[1] = cpu_to_be32(qp->remote_qpn);

	ohdr->bth[2] = cpu_to_be32(qp->r_ack_psn & IPATH_PSN_MASK);



	/*

	 * If we can send the ACK, clear the ACK state.

	 */

	if (ipath_verbs_send(qp, &hdr, hwords, NULL, 0) == 0) {

	writeq(hwords + 1, piobuf);



	if (dd->ipath_flags & IPATH_PIO_FLUSH_WC) {

		u32 *hdrp = (u32 *) &hdr;



		ipath_flush_wc();

		__iowrite32_copy(piobuf + 2, hdrp, hwords - 1);

		ipath_flush_wc();

		__raw_writel(hdrp[hwords - 1], piobuf + hwords + 1);

	} else

		__iowrite32_copy(piobuf + 2, (u32 *) &hdr, hwords);



	ipath_flush_wc();



	dev->n_unicast_xmit++;

	goto done;

	}



	/*

	 * We are out of PIO buffers at the moment.

	 * Pass responsibility for sending the ACK to the

	 * send tasklet so that when a PIO buffer becomes

	 * available, the ACK is sent ahead of other outgoing

	 * packets.

	 */

	dev->n_rc_qacks++;



queue_ack:

	spin_lock_irqsave(&qp->s_lock, flags);

	dev->n_rc_qacks++;

	qp->s_flags |= IPATH_S_ACK_PENDING;

	qp->s_nak_state = qp->r_nak_state;