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From: Sinan Kaya <okaya@codeaurora.org>
To: linux-alpha@vger.kernel.org, arnd@arndb.de, timur@codeaurora.org,
	sulrich@codeaurora.org, Matt Turner <mattst88@gmail.com>
Cc: linux-arm-msm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Richard Henderson <rth@twiddle.net>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	Philippe Ombredanne <pombredanne@nexb.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Kate Stewart <kstewart@linuxfoundation.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] alpha: io: reorder barriers to guarantee writeX() and iowriteX() ordering #2
Date: Fri, 20 Apr 2018 12:20:11 -0400	[thread overview]
Message-ID: <2fd54f7c-ff73-5935-a253-c924f4373cc6@codeaurora.org> (raw)
In-Reply-To: <b9d845ad-62af-d300-53d9-2b62f5da6c44@codeaurora.org>

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 <okaya@codeaurora.org>
>> Reported-by: Arnd Bergmann <arnd@arndb.de>
>> ---
>>  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.

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.

  reply	other threads:[~2018-04-20 16:20 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-16 22:16 Sinan Kaya
2018-04-17 18:43 ` Sinan Kaya
2018-04-20 16:20   ` Sinan Kaya [this message]
2018-05-01 22:48     ` Sinan Kaya
2018-05-09  2:57     ` Matt Turner

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