linux-kernel - Re: [PATCH v3] i2c: mediatek: i2c multi transfer optimization

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Message-ID: <20160412211355.GA1526@katana>
Date:	Tue, 12 Apr 2016 23:13:56 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Liguo Zhang <liguo.zhang@...iatek.com>
Cc:	srv_heupstream@...iatek.com,
	Matthias Brugger <matthias.bgg@...il.com>,
	Eddie Huang <eddie.huang@...iatek.com>,
	Xudong Chen <xudong.chen@...iatek.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v3] i2c: mediatek: i2c multi transfer optimization

Hi,

thanks for the submission!

On Tue, Mar 08, 2016 at 02:23:51AM +0800, Liguo Zhang wrote:
> Signal complete() in the i2c irq handler after one transfer done,
> and then wait_for_completion_timeout() will return, this procedure
> may cost much time, so only signal complete() when the entire
> transaction has been completed, it will reduce the entire transaction
> time.
> 
> Signed-off-by: Liguo Zhang <liguo.zhang@...iatek.com>

I wonder. You have less context switches, yes. On the other hand, you
likely have bigger interrupt latency because you do more stuff in the
interrupt handler. Is it really a gain in the end?

Regards,

   Wolfram


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