drivers/infiniband/sw/rdmavt/rc.c

// SPDX-License-Identifier: GPL-2.0 or BSD-3-Clause
/*
 * Copyright(c) 2016 Intel Corporation.
 */

#include <rdma/rdmavt_qp.h>
#include <rdma/ib_hdrs.h>

/*
 * Convert the AETH credit code into the number of credits.
 */
static const u16 credit_table[31] = {
	0,                      /* 0 */
	1,                      /* 1 */
	2,                      /* 2 */
	3,                      /* 3 */
	4,                      /* 4 */
	6,                      /* 5 */
	8,                      /* 6 */
	12,                     /* 7 */
	16,                     /* 8 */
	24,                     /* 9 */
	32,                     /* A */
	48,                     /* B */
	64,                     /* C */
	96,                     /* D */
	128,                    /* E */
	192,                    /* F */
	256,                    /* 10 */
	384,                    /* 11 */
	512,                    /* 12 */
	768,                    /* 13 */
	1024,                   /* 14 */
	1536,                   /* 15 */
	2048,                   /* 16 */
	3072,                   /* 17 */
	4096,                   /* 18 */
	6144,                   /* 19 */
	8192,                   /* 1A */
	12288,                  /* 1B */
	16384,                  /* 1C */
	24576,                  /* 1D */
	32768                   /* 1E */
};

/**
 * rvt_compute_aeth - compute the AETH (syndrome + MSN)
 * @qp: the queue pair to compute the AETH for
 *
 * Returns the AETH.
 */
__be32 rvt_compute_aeth(struct rvt_qp *qp)
{
	u32 aeth = qp->r_msn & IB_MSN_MASK;

	if (qp->ibqp.srq) {
		/*
		 * Shared receive queues don't generate credits.
		 * Set the credit field to the invalid value.
		 */
		aeth |= IB_AETH_CREDIT_INVAL << IB_AETH_CREDIT_SHIFT;
	} else {
		u32 min, max, x;
		u32 credits;
		u32 head;
		u32 tail;

		credits = READ_ONCE(qp->r_rq.kwq->count);
		if (credits == 0) {
			/* sanity check pointers before trusting them */
			if (qp->ip) {
				head = RDMA_READ_UAPI_ATOMIC(qp->r_rq.wq->head);
				tail = RDMA_READ_UAPI_ATOMIC(qp->r_rq.wq->tail);
			} else {
				head = READ_ONCE(qp->r_rq.kwq->head);
				tail = READ_ONCE(qp->r_rq.kwq->tail);
			}
			if (head >= qp->r_rq.size)
				head = 0;
			if (tail >= qp->r_rq.size)
				tail = 0;
			/*
			 * Compute the number of credits available (RWQEs).
			 * There is a small chance that the pair of reads are
			 * not atomic, which is OK, since the fuzziness is
			 * resolved as further ACKs go out.
			 */
			credits = rvt_get_rq_count(&qp->r_rq, head, tail);
		}
		/*
		 * Binary search the credit table to find the code to
		 * use.
		 */
		min = 0;
		max = 31;
		for (;;) {
			x = (min + max) / 2;
			if (credit_table[x] == credits)
				break;
			if (credit_table[x] > credits) {
				max = x;
			} else {
				if (min == x)
					break;
				min = x;
			}
		}
		aeth |= x << IB_AETH_CREDIT_SHIFT;
	}
	return cpu_to_be32(aeth);
}
EXPORT_SYMBOL(rvt_compute_aeth);

/**
 * rvt_get_credit - flush the send work queue of a QP
 * @qp: the qp who's send work queue to flush
 * @aeth: the Acknowledge Extended Transport Header
 *
 * The QP s_lock should be held.
 */
void rvt_get_credit(struct rvt_qp *qp, u32 aeth)
{
	struct rvt_dev_info *rdi = ib_to_rvt(qp->ibqp.device);
	u32 credit = (aeth >> IB_AETH_CREDIT_SHIFT) & IB_AETH_CREDIT_MASK;

	lockdep_assert_held(&qp->s_lock);
	/*
	 * If the credit is invalid, we can send
	 * as many packets as we like.  Otherwise, we have to
	 * honor the credit field.
	 */
	if (credit == IB_AETH_CREDIT_INVAL) {
		if (!(qp->s_flags & RVT_S_UNLIMITED_CREDIT)) {
			qp->s_flags |= RVT_S_UNLIMITED_CREDIT;
			if (qp->s_flags & RVT_S_WAIT_SSN_CREDIT) {
				qp->s_flags &= ~RVT_S_WAIT_SSN_CREDIT;
				rdi->driver_f.schedule_send(qp);
			}
		}
	} else if (!(qp->s_flags & RVT_S_UNLIMITED_CREDIT)) {
		/* Compute new LSN (i.e., MSN + credit) */
		credit = (aeth + credit_table[credit]) & IB_MSN_MASK;
		if (rvt_cmp_msn(credit, qp->s_lsn) > 0) {
			qp->s_lsn = credit;
			if (qp->s_flags & RVT_S_WAIT_SSN_CREDIT) {
				qp->s_flags &= ~RVT_S_WAIT_SSN_CREDIT;
				rdi->driver_f.schedule_send(qp);
			}
		}
	}
}
EXPORT_SYMBOL(rvt_get_credit);

/**
 * rvt_restart_sge - rewind the sge state for a wqe
 * @ss: the sge state pointer
 * @wqe: the wqe to rewind
 * @len: the data length from the start of the wqe in bytes
 *
 * Returns the remaining data length.
 */
u32 rvt_restart_sge(struct rvt_sge_state *ss, struct rvt_swqe *wqe, u32 len)
{
	ss->sge = wqe->sg_list[0];
	ss->sg_list = wqe->sg_list + 1;
	ss->num_sge = wqe->wr.num_sge;
	ss->total_len = wqe->length;
	rvt_skip_sge(ss, len, false);
	return wqe->length - len;
}
EXPORT_SYMBOL(rvt_restart_sge);