From: Mark Brown <broonie@kernel.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "Clément Léger" <clement.leger@bootlin.com>,
"Lee Jones" <lee.jones@linaro.org>,
"Rob Herring" <robh+dt@kernel.org>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
DTML <devicetree@vger.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Peng Fan" <peng.fan@nxp.com>,
"Sudeep Holla" <sudeep.holla@arm.com>,
"Alexandre Belloni" <alexandre.belloni@bootlin.com>
Subject: Re: [PATCH 2/3] syscon: add support for "syscon-smc" compatible
Date: Fri, 23 Jul 2021 17:41:58 +0100 [thread overview]
Message-ID: <20210723164158.GJ5221@sirena.org.uk> (raw)
In-Reply-To: <CAK8P3a1stoM2zRpkEBOLSFRxPy6Tabn6NgO-1sVRL4uq3wudaQ@mail.gmail.com>
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On Fri, Jul 23, 2021 at 06:07:44PM +0200, Arnd Bergmann wrote:
> There is also a problem with locking: In the case that both firmware and
> kernel have to access registers within a syscon area, you may need to
> have a semaphore to protect an atomic sequence of accesses, but since
> the interface only provides a single register load/store, there is no way for
> a kernel driver to serialize against a firmware-internal driver.
The standard solution to this for the read/modify/write case would be to
expose an explicit update_bits() operation (some hardware does this for
concurrency and/or bus bandwidth/latency reasons), though that doesn't
help with larger or multi-register sequences (and to be clear as I've
been saying I don't think we should do this at all).
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next prev parent reply other threads:[~2021-07-23 16:42 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 13:52 [PATCH 0/3] add SMC based regmap driver for secure syscon access Clément Léger
2021-07-23 13:52 ` [PATCH 1/3] regmap: add regmap using ARM SMCCC Clément Léger
2021-07-23 14:43 ` Mark Brown
2021-07-23 15:53 ` Clément Léger
2021-07-23 16:37 ` Mark Brown
2021-07-23 13:52 ` [PATCH 2/3] syscon: add support for "syscon-smc" compatible Clément Léger
2021-07-23 15:27 ` Lee Jones
2021-07-23 15:56 ` Clément Léger
2021-07-23 16:07 ` Arnd Bergmann
2021-07-23 16:41 ` Mark Brown [this message]
2021-07-24 12:36 ` Peng Fan (OSS)
2021-07-24 7:00 ` kernel test robot
2021-07-24 7:00 ` kernel test robot
2021-07-23 13:52 ` [PATCH 3/3] dt-bindings: mfd: add "syscon-smc" YAML description Clément Léger
2021-07-29 21:19 ` Rob Herring
2021-07-30 7:21 ` Clément Léger
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