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Date: Mon, 19 Feb 2024 15:38:31 +0100
Message-Id: <CZ94S0SE0WFN.1RS0SY3KNMWQQ@bootlin.com>
From: =?utf-8?q?Th=C3=A9o_Lebrun?= <theo.lebrun@bootlin.com>
Subject: Re: [PATCH 08/13] i2c: nomadik: replace jiffies by ktime for FIFO
 flushing timeout
Cc: "Andi Shyti" <andi.shyti@kernel.org>, "Rob Herring"
 <robh+dt@kernel.org>, "Krzysztof Kozlowski"
 <krzysztof.kozlowski+dt@linaro.org>, "Conor Dooley" <conor+dt@kernel.org>,
 "Thomas Bogendoerfer" <tsbogend@alpha.franken.de>,
 <linux-arm-kernel@lists.infradead.org>, <linux-i2c@vger.kernel.org>,
 <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
 <linux-mips@vger.kernel.org>, "Gregory Clement"
 <gregory.clement@bootlin.com>, "Vladimir Kondratiev"
 <vladimir.kondratiev@mobileye.com>, "Thomas Petazzoni"
 <thomas.petazzoni@bootlin.com>, "Tawfik Bayouk"
 <tawfik.bayouk@mobileye.com>
To: "Linus Walleij" <linus.walleij@linaro.org>
References: <20240215-mbly-i2c-v1-0-19a336e91dca@bootlin.com>
 <20240215-mbly-i2c-v1-8-19a336e91dca@bootlin.com>
 <CACRpkdbuTX50syD0CMFcZXBmAHw4nwpcSc-C1OOUQEA9WHqCwA@mail.gmail.com>
In-Reply-To: <CACRpkdbuTX50syD0CMFcZXBmAHw4nwpcSc-C1OOUQEA9WHqCwA@mail.gmail.com>

Hello,

On Mon Feb 19, 2024 at 3:21 PM CET, Linus Walleij wrote:
> On Thu, Feb 15, 2024 at 5:52=E2=80=AFPM Th=C3=A9o Lebrun <theo.lebrun@boo=
tlin.com> wrote:
>
> > The FIFO flush function uses a jiffies amount to detect timeouts as the
> > flushing is async. Replace with ktime to get more accurate precision
> > and support short timeouts.
> >
> > Signed-off-by: Th=C3=A9o Lebrun <theo.lebrun@bootlin.com>
>
> Excellent patch. Thanks.
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Somewhat related to this patch: while writing it, I noticed the total
timeout of flush_i2c_fifo() is 10 times the timeout. Without this
series, this means 10*200ms of busywaiting!

If you have an opinion on a more sensible option for this I could add a
patch to my V2. I don't know enough to pick a sensible value.

I'm unsure if it makes sense that the timeout of flush_i2c_fifo() is a
multiple of the transfer timeout. Does it make sense that those two
timeouts are correlated?

Big thanks for your review,

--
Th=C3=A9o Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com