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Date: Thu, 24 Apr 2014 11:41:15 +1000
From: NeilBrown <neilb@suse.de>
To: <balbi@ti.com>
Cc: Nishanth Menon <nm@ti.com>, Greg KH <gregkh@linuxfoundation.org>,
 <marcel@holtmann.org>, <gustavo@padovan.org>, <johan.hedberg@gmail.com>,
 <jslaby@suse.cz>, <grant.likely@linaro.org>, Linux Kernel Mailing List
 <linux-kernel@vger.kernel.org>, <linux-bluetooth@vger.kernel.org>,
 <linux-serial@vger.kernel.org>, <devicetree@vger.kernel.org>, Linux OMAP
 Mailing List <linux-omap@vger.kernel.org>, Tony Lindgren <tony@atomide.com>
Subject: Re: [PATCH 10/13] tty: serial: omap: remove some dead code
Message-ID: <20140424114115.51ab3f98@notabene.brown>
In-Reply-To: <20140424012100.GB13374@saruman.home>
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On Wed, 23 Apr 2014 20:21:00 -0500 Felipe Balbi <balbi@ti.com> wrote:

> I have no problem either way, just that unused code doesn't have to be
> sitting in the tree and I'm not entirely sure this GPIO should be
> handled by omap-serial.c, perhaps something more generic inside
> serial-core so other UART drivers can benefit from it.

Perhaps.  But there there are more people I need to convince :-)

>=20
> > On the other hand, if you can point out to me what I'm missing, and how=
 I can
> > solve my problem with any virtual GPIOs, I'm all ears.
> >=20
> > To make my problem simple and explicit:  I have a device attached to a =
UART
> > which has a separate regulator.  The regulator should be powered on if =
and
>=20
> So you're using DTR to power the GPIO and hoping that the regulator
> stabilizes quickly enough so that by the time your open() finishes you
> don't have to add nonsensical msleep() calls before writing to the
> device. Sounds a bit fragile to me.

The gpio_set call is synchronous, and the gpio-regulator driver could add a
delay (I think).


>=20
> > only if the /dev/ttyXX interface to the UART is open.  The device is a
> > bluetooth transceiver.
>=20
> considering this is a BTUART device, why didn't you do this at the ldisc
> level ? hci_uart_open() sounds like a good choice from a quick thinking.
>=20

I'll have a look into that, thanks.

NeilBrown


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