From: Sinan Kaya <okaya@codeaurora.org>
To: Mikulas Patocka <mpatocka@redhat.com>, Arnd Bergmann <arnd@arndb.de>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>,
Matt Turner <mattst88@gmail.com>,
linux-alpha@vger.kernel.org, okaya@kernel.org,
Will Deacon <will.deacon@arm.com>,
linux-arch <linux-arch@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: Alpha Avanti broken by 9ce8654323d69273b4977f76f11c9e2d345ab130
Date: Wed, 22 Aug 2018 15:38:46 -0400 [thread overview]
Message-ID: <09c561cf-541c-219a-f19b-4ecfaf9a0f02@codeaurora.org> (raw)
In-Reply-To: <alpine.LRH.2.02.1808221336400.12083@file01.intranet.prod.int.rdu2.redhat.com>
On 8/22/2018 1:47 PM, Mikulas Patocka wrote:
> If ARM guarantees that the accesses to a given device are not reordered -
> then the barriers in readl and writel are superfluous.
It is not. ARM only guarantees ordering of read/write transactions targeting
a device not memory.
example:
write memory
raw write to device
or
raw read from device
read memory
these can bypass each other on ARM unless a barrier is placed in the right
place either via readl()/writel() or explicitly.
raw write to device
raw write to device
or
raw write to device
raw read from device
or
raw read from device
raw read from device
are guaranteed to be ordered on ARM without needing any explicit barrier.
next prev parent reply other threads:[~2018-08-22 23:05 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <alpine.LRH.2.02.1808161556450.13597@file01.intranet.prod.int.rdu2.redhat.com>
[not found] ` <CAK8P3a09jqhxYah6SZUjbku3NGiPX2PyhA+jJNG7VzJUnwUZKQ@mail.gmail.com>
[not found] ` <alpine.LFD.2.21.1808172254110.26277@eddie.linux-mips.org>
[not found] ` <CAK8P3a3kq35zny70Mnzmk9Tzfm2U9DLPNMyBrursPtOHpOyJSw@mail.gmail.com>
[not found] ` <28597e7477418ac7cb646e2edb5e6da2@codeaurora.org>
[not found] ` <alpine.LRH.2.02.1808201010200.15146@file01.intranet.prod.int.rdu2.redhat.com>
[not found] ` <CAK8P3a3ribyvLwXaB=J4dcTwD9aYc64hfw+ORTFtyvOHuS-U0g@mail.gmail.com>
[not found] ` <alpine.LRH.2.02.1808201740170.2948@file01.intranet.prod.int.rdu2.redhat.com>
[not found] ` <CAK8P3a1E2V-zFN5PpJ868L=6CgTykkyjtF6-aTsCCh6QqryUig@mail.gmail.com>
[not found] ` <alpine.LRH.2.02.1808210814250.24287@file01.intranet.prod.int.rdu2.redhat.com>
[not found] ` <CAK8P3a3vJK1caKpDqkEhMG=8n8N3U6ckqe=0f2fjUJwk-9K0XA@mail.gmail.com>
[not found] ` <alpine.LRH.2.02.1808220743270.12730@file01.intranet.prod.int.rdu2.redhat.com>
[not found] ` <21c0bd37-0ae7-db8f-76b8-6552c30faa4f@codeaurora.org>
[not found] ` <alpine.LFD.2.21.1808221609000.26277@eddie.linux-mips.org>
2018-08-22 15:50 ` Alpha Avanti broken by 9ce8654323d69273b4977f76f11c9e2d345ab130 Mikulas Patocka
2018-08-22 16:06 ` Arnd Bergmann
2018-08-22 17:20 ` Maciej W. Rozycki
2018-08-22 17:47 ` Mikulas Patocka
2018-08-22 19:38 ` Sinan Kaya [this message]
2018-08-22 19:56 ` Mikulas Patocka
2018-08-22 20:03 ` Will Deacon
2018-08-22 20:06 ` Sinan Kaya
2018-08-22 20:12 ` Will Deacon
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