From: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
To: Sean Hefty <sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH 03/11] RDMA/cxgb4: CQ size must be IQ size - 2.
Date: Thu, 20 May 2010 17:16:49 -0500 [thread overview]
Message-ID: <4BF5B4D1.1010504@opengridcomputing.com> (raw)
In-Reply-To: <27BBA4336B784434AAE16BB1126AD59C-Zpru7NauK7drdx17CPfAsdBPR1lH4CV8@public.gmane.org>
Sean Hefty wrote:
>> /* account for the status page. */
>> entries++;
>>
>> + /* IQ needs one extra entry to differentiate full vs empty. */
>> + entries++;
>> +
>> /*
>> * entries must be multiple of 16 for HW.
>> */
>> @@ -801,7 +804,7 @@ struct ib_cq *c4iw_create_cq(struct ib_device *ibdev, int
>> entries,
>>
>> chp->rhp = rhp;
>> chp->cq.size--; /* status page */
>> - chp->ibcq.cqe = chp->cq.size;
>> + chp->ibcq.cqe = chp->cq.size - 1;
>>
>
> Why does the status page adjust using size--, but we use size - 1 for the extra
> entry?
>
>
chp->cq.size is the actual number of entries that can write-to by the
HW. But since one must always be available to detect "full" vs "empty",
we tell the ULP that the size is one less than that.
Steve.
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next prev parent reply other threads:[~2010-05-20 22:16 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-20 21:57 [PATCH 01/11] RDMA/cxgb4: Detach from the LLD after unregistering with the RDMA core Steve Wise
[not found] ` <20100520215727.32394.90669.stgit-T4OLL4TyM9aNDNWfRnPdfg@public.gmane.org>
2010-05-20 21:57 ` [PATCH 02/11] RDMA/cxgb4: register rdma provider based on LLD state_change events Steve Wise
2010-05-20 21:57 ` [PATCH 03/11] RDMA/cxgb4: CQ size must be IQ size - 2 Steve Wise
[not found] ` <20100520215738.32394.60360.stgit-T4OLL4TyM9aNDNWfRnPdfg@public.gmane.org>
2010-05-20 22:08 ` Sean Hefty
[not found] ` <27BBA4336B784434AAE16BB1126AD59C-Zpru7NauK7drdx17CPfAsdBPR1lH4CV8@public.gmane.org>
2010-05-20 22:16 ` Steve Wise [this message]
2010-05-20 21:57 ` [PATCH 04/11] RDMA/cxgb4: Optimize CQ overflow detection Steve Wise
2010-05-20 21:57 ` [PATCH 05/11] RDMA/cxgb4: Fix overflow bug in cq arm Steve Wise
2010-05-20 21:57 ` [PATCH 06/11] RDMA/cxgb4: Return proper errors in fastreg mr/pbl allocation Steve Wise
2010-05-20 21:57 ` [PATCH 07/11] RDMA/cxgb4: Don't limit fastreg page list depth Steve Wise
2010-05-20 21:58 ` [PATCH 08/11] RDMA/cxgb4: Update some HW limits Steve Wise
2010-05-20 21:58 ` [PATCH 09/11] RDMA/cxgb4: Set fence flag for inv-local-stag work requests Steve Wise
2010-05-20 21:58 ` [PATCH 10/11] RDMA/cxgb4: Support IB_WR_READ_WITH_INV opcode Steve Wise
2010-05-20 21:58 ` [PATCH 11/11] RDMA/cxgb4: Only insert sq qid in lookup table Steve Wise
2010-05-25 4:08 ` [PATCH 01/11] RDMA/cxgb4: Detach from the LLD after unregistering with the RDMA core Roland Dreier
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