linux-kernel - Re: [PATCH v3 18/18] infiniband: cxgb4: Eliminate duplicate barriers on weakly-ordered archs

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Message-ID: <CAOZdJXWMmsSUXpT_XVboXM5DRHzt0=EXL9mFNPm0bWtTxhU_QA@mail.gmail.com>
Date:   Fri, 16 Mar 2018 23:30:59 -0500
From:   Timur Tabi <timur@...eaurora.org>
To:     Sinan Kaya <okaya@...eaurora.org>
Cc:     Steve Wise <swise@...ngridcomputing.com>,
        netdev <netdev@...r.kernel.org>,
        Timur Tabi <timur@...eaurora.org>, sulrich@...eaurora.org,
        Casey Leedom <leedom@...lsio.com>,
        Steve Wise <swise@...lsio.com>, linux-rdma@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Doug Ledford <dledford@...hat.com>,
        Michael Werner <werner@...lsio.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 18/18] infiniband: cxgb4: Eliminate duplicate barriers
 on weakly-ordered archs

On Fri, Mar 16, 2018 at 11:25 PM, Sinan Kaya <okaya@...eaurora.org> wrote:
> @@ -477,15 +477,16 @@ static inline void t4_ring_sq_db(struct t4_wq *wq, u16 inc, union t4_wr *wqe)
>                                  (u64 *)wqe);
>                 } else {
>                         pr_debug("DB wq->sq.pidx = %d\n", wq->sq.pidx);
> -                       writel(PIDX_T5_V(inc) | QID_V(wq->sq.bar2_qid),
> -                              wq->sq.bar2_va + SGE_UDB_KDOORBELL);
> +                       __raw_writel(PIDX_T5_V(inc) | QID_V(wq->sq.bar2_qid),

I think Jason might be right that drivers shouldn't be calling the
__raw_write functions.  You definitely need to run this by the PPC
developers, specifically Ben Herrenschmidt.


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