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From: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
To: Jonathan Cameron <jic23-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: "Vianney le Clément de Saint-Marcq"
	<vianney.leclement-buIOx9BAs4sybS5Ee8rs3A@public.gmane.org>,
	linux-iio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	"Peter Meerwald" <pmeerw-jW+XmwGofnusTnJN9+BGXg@public.gmane.org>,
	devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	"Arnout Vandecappelle (Essensium/Mind)"
	<arnout-agwphqFHkxc@public.gmane.org>,
	"Linux I2C" <linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"Wolfram Sang" <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
Subject: Re: [PATCH 6/7] iio: mlx90614: Add power management
Date: Mon, 9 Mar 2015 17:43:08 +0100	[thread overview]
Message-ID: <20150309164308.GA2320@katana> (raw)
In-Reply-To: <54FDBEB7.8030403-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

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On Mon, Mar 09, 2015 at 03:39:35PM +0000, Jonathan Cameron wrote:
> On 25/02/15 15:55, Vianney le Clément de Saint-Marcq wrote:
> > Add support for system sleep and runtime power management.
> > 
> > To wake up the device, the SDA line should be held low for at least 33ms
> > while SCL is high.  As this is not possible using the i2c API (and not
> > supported by all i2c adapters), a GPIO connected to the SDA line is
> > needed.  The GPIO is named "wakeup" and can be specified in a device
> > tree with the "wakeup-gpios" binding.
> Needs some i2c specialist input on this!  As you mentioned it is liable
> to be controversial.  Wolfram, is this a one off special or do
> any other devices do this sort of magic?

s/magic/insanity/ :)

I have never heard of something like this. Unsuprisingly, I can
not recommend doing it this way. But we all know hardware...

And while we could think about reusing the bus_recovery_infrastructure,
I don't think it is worth the hazzle. So, doing this GPIO fallback may
well be the best we can do now.


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  parent reply	other threads:[~2015-03-09 16:43 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-25 15:55 [PATCH 0/7] iio: mlx90614 enhancements Vianney le Clément de Saint-Marcq
     [not found] ` <1424879712-28304-1-git-send-email-vianney.leclement-buIOx9BAs4sybS5Ee8rs3A@public.gmane.org>
2015-02-25 15:55   ` [PATCH 6/7] iio: mlx90614: Add power management Vianney le Clément de Saint-Marcq
     [not found]     ` <1424879712-28304-7-git-send-email-vianney.leclement-buIOx9BAs4sybS5Ee8rs3A@public.gmane.org>
2015-03-09 15:39       ` Jonathan Cameron
     [not found]         ` <54FDBEB7.8030403-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2015-03-09 15:42           ` Jonathan Cameron
2015-03-09 16:43           ` Wolfram Sang [this message]
2015-03-12 10:30             ` Jonathan Cameron

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