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Date: Mon, 04 Mar 2024 11:14:53 +0100
Message-Id: <CZKVXSULAGXC.1C5PDQJ6KCHN@bootlin.com>
Subject: Re: [PATCH v2 06/11] i2c: nomadik: support short xfer timeouts
 using waitqueue & hrtimer
Cc: "Linus Walleij" <linus.walleij@linaro.org>, "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: "Wolfram Sang" <wsa@kernel.org>
From: =?utf-8?q?Th=C3=A9o_Lebrun?= <theo.lebrun@bootlin.com>
References: <20240229-mbly-i2c-v2-0-b32ed18c098c@bootlin.com>
 <20240229-mbly-i2c-v2-6-b32ed18c098c@bootlin.com>
 <ZeWRyuN8v-VnraQA@ninjato>
In-Reply-To: <ZeWRyuN8v-VnraQA@ninjato>

Hello,

On Mon Mar 4, 2024 at 10:18 AM CET, Wolfram Sang wrote:
> On Thu, Feb 29, 2024 at 07:10:54PM +0100, Th=C3=A9o Lebrun wrote:
> > Replace the completion by a waitqueue for synchronization from IRQ
> > handler to task. For short timeouts, use hrtimers, else use timers.
> > Usecase: avoid blocking the I2C bus for too long when an issue occurs.
> >=20
> > The threshold picked is one jiffy: if timeout is below that, use
> > hrtimers. This threshold is NOT configurable.
> >=20
> > Implement behavior but do NOT change fetching of timeout. This means th=
e
> > timeout is unchanged (200ms) and the hrtimer case will never trigger.
> >=20
> > A waitqueue is used because it supports both desired timeout approaches=
.
> > See wait_event_timeout() and wait_event_hrtimeout(). An atomic boolean
> > serves as synchronization condition.
> >=20
> > Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> > Signed-off-by: Th=C3=A9o Lebrun <theo.lebrun@bootlin.com>
>
> Largely:
>
> Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Thanks for the reviews Wolfram.

> Nit:
>
> > -	int				timeout;
> > +	int				timeout_usecs;
>
> I think 'unsigned' makes a lot of sense here. Maybe u32 even?

Yes unsigned would make sense. unsigned int or u32, I wouldn't know
which to pick.

Regards,

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