RDMA/hw/hfi1/iowait: Demote half-completed kernel-doc and fix formatting issue in another

Fixes the following W=1 kernel build warning(s):

drivers/infiniband/hw/hfi1/iowait.c:52: warning: Function parameter or member 'tidfunc' not described in 'iowait_init'
drivers/infiniband/hw/hfi1/iowait.c:52: warning: Function parameter or member 'wakeup' not described in 'iowait_init'
drivers/infiniband/hw/hfi1/iowait.c:52: warning: Function parameter or member 'sdma_drained' not described in 'iowait_init'
drivers/infiniband/hw/hfi1/iowait.c:52: warning: Function parameter or member 'init_priority' not described in 'iowait_init'
drivers/infiniband/hw/hfi1/iowait.c:52: warning: Excess function parameter 'resume' description in 'iowait_init'
drivers/infiniband/hw/hfi1/iowait.c:94: warning: Function parameter or member 'w' not described in 'iowait_set_work_flag'

Link: https://lore.kernel.org/r/20210126124732.3320971-4-lee.jones@linaro.org
Cc: Mike Marciniszyn <mike.marciniszyn@cornelisnetworks.com>
Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-rdma@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

IB/hfi1: Don't cancel unused work item

In the iowait structure, two iowait_work entries were included to queue a
given object: one for normal IB operations, and the other for TID RDMA
operations. For non-TID RDMA operations, the iowait_work structure for TID
RDMA is initialized to contain a NULL function (not used). When the QP is
reset, the function iowait_cancel_work will be called to cancel any
pending work. The problem is that this function will call
cancel_work_sync() for both iowait_work entries, even though the one for
TID RDMA is not used at all. Eventually, the call cascades to
__flush_work(), wherein a WARN_ON will be triggered due to the fact that
work->func is NULL.

The WARN_ON was introduced in commit 4d43d395fed1 ("workqueue: Try to
catch flush_work() without INIT_WORK().")

This patch fixes the issue by making sure that a work function is present
for TID RDMA before calling cancel_work_sync in iowait_cancel_work.

Fixes: 4d43d395fed1 ("workqueue: Try to catch flush_work() without INIT_WORK().")
Fixes: 5da0fc9dbf89 ("IB/hfi1: Prepare resource waits for dual leg")
Link: https://lore.kernel.org/r/20191219211941.58387.39883.stgit@awfm-01.aw.intel.com
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

IB/hfi1: Prioritize the sending of ACK packets

ACK packets are generally associated with request completion and resource
release and therefore should be sent first. This patch optimizes the
send engine by using the following policies:
(1) QPs with RVT_S_ACK_PENDING bit set in qp->s_flags or qpriv->s_flags
should have their priority incremented;
(2) QPs with ACK or TID-ACK packet queued should have their priority
incremented;
(3) When a QP is queued to the wait list due to resource constraints, it
will be queued to the head if it has ACK packet to send;
(4) When selecting qps to run from the wait list, the one with the highest
priority and starve_cnt will be selected; each priority will be equivalent
to a fixed number of starve_cnt (16).

Reviewed-by: Mitko Haralanov <mitko.haralanov@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

IB/hfi1: Add static trace for iowait

This patch adds the static trace for resource wait.

Reviewed-by: Mitko Haralanov <mitko.haralanov@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

IB/hfi1: Prepare resource waits for dual leg

Current implementation allows each qp to have only one send engine. As
such, each qp has only one list to queue prebuilt packets when send engine
resources are not available. To improve performance, it is desired to
support multiple send engines for each qp.

This patch creates the framework to support two send engines
(two legs) for each qp for the TID RDMA protocol, which can be easily
extended to support more send engines. It achieves the goal by creating a
leg specific struct, iowait_work in the iowait struct, to hold the
work_struct and the tx_list as well as a pointer to the parent iowait
struct.

The hfi1_pkt_state now has an additional field to record the current legs
work structure and that is now passed to all egress waiters to determine
the leg that needs to wait via a new iowait helper. The APIs are adjusted
to use the new leg specific struct as required.

Many new and modified helpers are added to support this change.

Reviewed-by: Mitko Haralanov <mitko.haralanov@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>