gt; <ariel.el...@cavium.com>; Doug Ledford <dledf...@redhat.com>; Jason
> > > Gunthorpe <j...@ziepe.ca>; linux-kernel@vger.kernel.org
> > > Subject: Re: [PATCH v5 3/3] RDMA/qedr: eliminate duplicate barriers
> > > on weakly-ordered archs #2
> > >
> &g
> To: linux-r...@vger.kernel.org; ti...@codeaurora.org;
> > > sulr...@codeaurora.org
> > > Cc: linux-arm-...@vger.kernel.org;
> > > linux-arm-ker...@lists.infradead.org;
> > > Kalderon, Michal ; Elior, Ariel
> > > ; Doug Ledford ; Jason
> > > Gu
vger.kernel.org; linux-arm-ker...@lists.infradead.org;
> > Kalderon, Michal <michal.kalde...@cavium.com>; Elior, Ariel
> > <ariel.el...@cavium.com>; Doug Ledford <dledf...@redhat.com>; Jason
> > Gunthorpe <j...@ziepe.ca>; linux-kernel@vger.kernel.org
vger.kernel.org; linux-arm-ker...@lists.infradead.org;
> > Kalderon, Michal ; Elior, Ariel
> > ; Doug Ledford ; Jason
> > Gunthorpe ; linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH v5 3/3] RDMA/qedr: eliminate duplicate barriers on
> > weakly-ordered archs #2
>
On 4/3/2018 3:42 AM, Kalderon, Michal wrote:
> The wmb before writel are used to make sure the
> HW observes the changes in memory before we trigger the doorbell.
According to Linus, writel() guarantees observability. No extra
barrier is necessary.
On 4/3/2018 3:42 AM, Kalderon, Michal wrote:
> The wmb before writel are used to make sure the
> HW observes the changes in memory before we trigger the doorbell.
According to Linus, writel() guarantees observability. No extra
barrier is necessary.
l.kalde...@cavium.com>; Elior, Ariel
> <ariel.el...@cavium.com>; Doug Ledford <dledf...@redhat.com>; Jason
> Gunthorpe <j...@ziepe.ca>; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v5 3/3] RDMA/qedr: eliminate duplicate barriers on
> weakly-ordered archs #2
>
l
> ; Doug Ledford ; Jason
> Gunthorpe ; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v5 3/3] RDMA/qedr: eliminate duplicate barriers on
> weakly-ordered archs #2
>
> On 3/22/2018 12:26 PM, Sinan Kaya wrote:
> > @@ -860,7 +860,7 @@ static void doorbell_cq(struct qedr
On 3/22/2018 12:26 PM, Sinan Kaya wrote:
> @@ -860,7 +860,7 @@ static void doorbell_cq(struct qedr_cq *cq, u32 cons, u8
> flags)
> wmb();
> cq->db.data.agg_flags = flags;
> cq->db.data.value = cpu_to_le32(cons);
> - writeq(cq->db.raw, cq->db_addr);
> +
On 3/22/2018 12:26 PM, Sinan Kaya wrote:
> @@ -860,7 +860,7 @@ static void doorbell_cq(struct qedr_cq *cq, u32 cons, u8
> flags)
> wmb();
> cq->db.data.agg_flags = flags;
> cq->db.data.value = cpu_to_le32(cons);
> - writeq(cq->db.raw, cq->db_addr);
> +
Code includes wmb() followed by writel() in multiple places. writel()
already has a barrier on some architectures like arm64.
This ends up CPU observing two barriers back to back before executing the
register write.
Since code already has an explicit barrier call, changing writel() to
Code includes wmb() followed by writel() in multiple places. writel()
already has a barrier on some architectures like arm64.
This ends up CPU observing two barriers back to back before executing the
register write.
Since code already has an explicit barrier call, changing writel() to
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