linux-kernel - Re: spi-imx: wait_for_completion should timeout even in non-DMA transfer cases

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Message-ID: <20150922172919.GK30445@sirena.org.uk>
Date:	Tue, 22 Sep 2015 10:29:19 -0700
From:	Mark Brown <broonie@...nel.org>
To:	Jean-Michel Hautbois <jean-michel.hautbois@...-labs.com>
Cc:	linux-spi@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: spi-imx: wait_for_completion should timeout even in non-DMA
 transfer cases

On Mon, Sep 21, 2015 at 11:08:55AM +0200, Jean-Michel Hautbois wrote:
> 2015-09-19 19:56 GMT+02:00 Mark Brown <broonie@...nel.org>:

> > A calculated timeout is probably best.

> Well, it depends...
> If you have a 20MHz clock, then you can transfer a byte in 4µs.
> As most of the time pio_transfer is used for 8 to 32 bytes max, it
> would be irrelevant to use such a small timeout.
> I can obviously do it, but not sure if using a small (say, 100ms)
> timeout would not be better.

You want a minimum threashold, yes, but you also need to be able toc ope
with larger transfers too so need to be able to raise that where
appropriate.

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