linux-kernel - Re: [PATCH 2/2] iio: ti_am335x_adc: Take touchscreen channels into account for conversion timeout

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Message-ID: <20130923164637.GF27515@raspi>
Date:	Mon, 23 Sep 2013 18:46:37 +0200
From:	Matthias Kaehlcke <matthias.list@...hlcke.net>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	Jonathan Cameron <jic23@....ac.uk>,
	"Patil, Rachna" <rachna@...com>, Felipe Balbi <balbi@...com>,
	Pantelis Antoniou <panto@...oniou-consulting.com>,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] iio: ti_am335x_adc: Take touchscreen channels into
 account for conversion timeout

Hi Sebastian,

El Mon, Sep 23, 2013 at 03:31:14PM +0200 Sebastian Andrzej Siewior ha dit:

> On 09/10/2013 11:02 PM, Matthias Kaehlcke wrote:
> > The calculation of the old conversion timeout value was based on the number of
> > channels used by this driver. This doesn't take into account that other channels
> > can be used by the touchscreen driver. Adjust the timeout value to the maximum
> > if the touchscreen driver is enabled
> 
> What bug / miss behave are you trying to fix?

I ran into timeouts when using the touchscreen driver at the same time
as the general purpose ADC and reviewed the timeout calculations. I found
that the IDLE_TIMEOUT value is/was wrong (I submitted another patch
for this) and that the ADC driver doesn't take into account the
steps used by the touchscreen driver

> The difference in timming is minimal and therefore I would prefer to get
> rid of this ifdef and assume the max value of those two instead.

Jonathan also expressed his concerns about this, I submitted a
follow-up patch without the ifdef (https://lkml.org/lkml/2013/9/16/460).
I would appreciate your comments on this patch

note that the timing difference isn't that minimal with the correct
IDLE_TIMEOUT (~100us instead of 10us), it sums up to a max timeout of
~1.6ms (16 steps) and we are busy looping (though in the non-error
case we will bail out as soon as the conversion cycle is finished)

best regards

-- 
Matthias Kaehlcke
Embedded Linux Developer
Amsterdam

    In the absence of clearly-defined goals, we become strangely loyal to
      performing daily trivia until ultimately we become enslaved by it
                           (Robert Heinlein)
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