From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH v4 3/6] RDMA/i40iw: Eliminate duplicate barriers on weakly-ordered archs Date: Tue, 20 Mar 2018 08:56:26 -0600 Message-ID: <20180320145626.GJ19744@ziepe.ca> References: <1521514068-8856-1-git-send-email-okaya@codeaurora.org> <1521514068-8856-4-git-send-email-okaya@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1521514068-8856-4-git-send-email-okaya@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org To: Sinan Kaya Cc: linux-rdma@vger.kernel.org, timur@codeaurora.org, sulrich@codeaurora.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Faisal Latif , Shiraz Saleem , Doug Ledford , linux-kernel@vger.kernel.org List-Id: linux-arm-msm@vger.kernel.org On Mon, Mar 19, 2018 at 10:47:45PM -0400, Sinan Kaya wrote: > Code includes wmb() followed by writel(). 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. > > Create a new wrapper function with relaxed write operator. Use the new > wrapper when a write is following a wmb(). > > Since code already has an explicit barrier call, changing writel() to > writel_relaxed(). > > Signed-off-by: Sinan Kaya > drivers/infiniband/hw/i40iw/i40iw_ctrl.c | 6 ++++-- > drivers/infiniband/hw/i40iw/i40iw_osdep.h | 1 + > drivers/infiniband/hw/i40iw/i40iw_uk.c | 2 +- > drivers/infiniband/hw/i40iw/i40iw_utils.c | 11 +++++++++++ > 4 files changed, 17 insertions(+), 3 deletions(-) The one looks fine Reviewed-by: Jason Gunthorpe Jason From mboxrd@z Thu Jan 1 00:00:00 1970 From: jgg@ziepe.ca (Jason Gunthorpe) Date: Tue, 20 Mar 2018 08:56:26 -0600 Subject: [PATCH v4 3/6] RDMA/i40iw: Eliminate duplicate barriers on weakly-ordered archs In-Reply-To: <1521514068-8856-4-git-send-email-okaya@codeaurora.org> References: <1521514068-8856-1-git-send-email-okaya@codeaurora.org> <1521514068-8856-4-git-send-email-okaya@codeaurora.org> Message-ID: <20180320145626.GJ19744@ziepe.ca> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Mar 19, 2018 at 10:47:45PM -0400, Sinan Kaya wrote: > Code includes wmb() followed by writel(). 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. > > Create a new wrapper function with relaxed write operator. Use the new > wrapper when a write is following a wmb(). > > Since code already has an explicit barrier call, changing writel() to > writel_relaxed(). > > Signed-off-by: Sinan Kaya > drivers/infiniband/hw/i40iw/i40iw_ctrl.c | 6 ++++-- > drivers/infiniband/hw/i40iw/i40iw_osdep.h | 1 + > drivers/infiniband/hw/i40iw/i40iw_uk.c | 2 +- > drivers/infiniband/hw/i40iw/i40iw_utils.c | 11 +++++++++++ > 4 files changed, 17 insertions(+), 3 deletions(-) The one looks fine Reviewed-by: Jason Gunthorpe Jason