From: "Arnd Bergmann" <arnd@arndb.de>
To: "Stefan Eichenberger" <eichest@gmail.com>,
o.rempel@pengutronix.de,
"Pengutronix Kernel Team" <kernel@pengutronix.de>,
"Andi Shyti" <andi.shyti@kernel.org>,
"Shawn Guo" <shawnguo@kernel.org>,
"Sascha Hauer" <s.hauer@pengutronix.de>,
"Fabio Estevam" <festevam@gmail.com>,
"Frank Li" <Frank.Li@nxp.com>
Cc: linux-i2c@vger.kernel.org, imx@lists.linux.dev,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
"Francesco Dolcini" <francesco.dolcini@toradex.com>,
"Stefan Eichenberger" <stefan.eichenberger@toradex.com>
Subject: Re: [PATCH v4 3/4] i2c: imx: use readb_relaxed and writeb_relaxed
Date: Wed, 02 Oct 2024 11:51:22 +0000 [thread overview]
Message-ID: <6b070948-cf02-4f13-a220-0f6cfa21c41a@app.fastmail.com> (raw)
In-Reply-To: <20241002112020.23913-4-eichest@gmail.com>
On Wed, Oct 2, 2024, at 11:19, Stefan Eichenberger wrote:
> From: Stefan Eichenberger <stefan.eichenberger@toradex.com>
>
> Use the relaxed version of readb and writeb to reduce overhead. It is
> safe to use the relaxed version because we either do not rely on dma
> completion, or we use a dma callback to ensure that the dma transfer is
> complete before we continue.
I would still consider this a bug in general, you should
never default to the unsafe variants.
If there is a codepath that needs the barrierless version,
please add imx_i2c_write_reg_relaxed()/imx_i2c_read_reg_relaxed()
helpers that use those only in the places where it makes
a measurable difference, with a comment that explains
the usage.
Arnd
next prev parent reply other threads:[~2024-10-02 11:51 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-02 11:19 [PATCH v4 0/4] i2c: imx: prevent rescheduling in non-dma mode Stefan Eichenberger
2024-10-02 11:19 ` [PATCH v4 1/4] i2c: imx: only poll for bus busy in multi master mode Stefan Eichenberger
2024-10-02 14:40 ` Lucas Stach
2024-10-02 14:56 ` Stefan Eichenberger
2024-10-02 15:16 ` Lucas Stach
2024-10-02 11:19 ` [PATCH v4 2/4] i2c: imx: separate atomic, dma and non-dma use case Stefan Eichenberger
2024-10-02 11:19 ` [PATCH v4 3/4] i2c: imx: use readb_relaxed and writeb_relaxed Stefan Eichenberger
2024-10-02 11:51 ` Arnd Bergmann [this message]
2024-10-02 13:08 ` Stefan Eichenberger
2024-10-02 13:36 ` Arnd Bergmann
2024-10-02 14:36 ` Stefan Eichenberger
2024-10-02 11:19 ` [PATCH v4 4/4] i2c: imx: prevent rescheduling in non dma mode Stefan Eichenberger
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