From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sinan Kaya Subject: Re: [PATCH] alpha: io: reorder barriers to guarantee writeX() and iowriteX() ordering #2 Date: Tue, 1 May 2018 18:48:02 -0400 Message-ID: References: <1523917017-28084-1-git-send-email-okaya@codeaurora.org> <2fd54f7c-ff73-5935-a253-c924f4373cc6@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <2fd54f7c-ff73-5935-a253-c924f4373cc6@codeaurora.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: linux-alpha@vger.kernel.org, arnd@arndb.de, timur@codeaurora.org, sulrich@codeaurora.org, Matt Turner Cc: linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Richard Henderson , Ivan Kokshaysky , Philippe Ombredanne , Greg Kroah-Hartman , Thomas Gleixner , Kate Stewart , linux-kernel@vger.kernel.org List-Id: linux-arm-msm@vger.kernel.org On 4/20/2018 12:20 PM, Sinan Kaya wrote: > Hi Matt, > > On 4/17/2018 2:43 PM, Sinan Kaya wrote: >> On 4/16/2018 6:16 PM, Sinan Kaya wrote: >>> memory-barriers.txt has been updated with the following requirement. >>> >>> "When using writel(), a prior wmb() is not needed to guarantee that the >>> cache coherent memory writes have completed before writing to the MMIO >>> region." >>> >>> Current writeX() and iowriteX() implementations on alpha are not >>> satisfying this requirement as the barrier is after the register write. >>> >>> Move mb() in writeX() and iowriteX() functions to guarantee that HW >>> observes memory changes before performing register operations. >>> >>> Signed-off-by: Sinan Kaya >>> Reported-by: Arnd Bergmann >>> --- >>> arch/alpha/kernel/io.c | 14 +++++++------- >>> 1 file changed, 7 insertions(+), 7 deletions(-) >> >> Sorry for catching this late but this also needs to go to 4.17 after >> review. >> >> I missed the writel() implementation on arch/alpha/kernel/io.c file >> on my first patch. >> > > Can you also queue this for 4.17? > > There are already drivers checked into 4.17 that dropped the unnecessary > barriers. > > I really hate to see Alpha broken because of this. ping. > > Sinan > -- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.