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From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Alexandre Courbot <gnurou@gmail.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] gpio: support for GPIO forwarding
Date: Thu, 8 Jan 2015 10:25:10 +0200	[thread overview]
Message-ID: <20150108082510.GA19346@kuha.fi.intel.com> (raw)
In-Reply-To: <1418890998-23811-1-git-send-email-heikki.krogerus@linux.intel.com>

On Thu, Dec 18, 2014 at 10:23:18AM +0200, Heikki Krogerus wrote:
> This makes it possible to assign GPIOs at runtime. The
> motivation for it is because of need to forward GPIOs from
> one device to an other. That feature may be useful for
> example with some mfd devices, but initially it is needed
> because on some Intel Braswell based ACPI platforms the GPIO
> resources controlling signals of the USB PHY are given to
> the controller device object for whatever reason, so the
> driver of that controller needs be able to pass them to the
> PHY device somehow.
> 
> So basically this is meant to allow patching of bad (bad
> from Linux kernels point of view) hardware descriptions
> provided by system fw in the drivers.
> 
> Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> ---
> 
> Hi,
> 
> I'm sending this first as a RFC in case you guys have some better
> idea how to solve our problem. I actually already have couple
> platforms where the GPIO resources are given to the "wrong" device
> objects now.
> 
> Originally we were thinking about simply handling our problem with
> hacks to the PHY drivers, basically also checking if the parent has
> GPIOs. That would only work if the controller is always the parent,
> which it's not, but even if it was, it would be too risky. The PHY
> drivers don't know which controller they are attached to, so what is
> to say that the GPIOs aren't really attached to the controller.
> 
> So the safest way to handle our problem is to deal with it in quirks
> in the controller drivers. Solving it by bouncing the GPIOs did not
> feel ideal there doesn't seem to be any other way. The API is copied
> from clkdev (clk_register_clkdev). In the end it's really only one
> function for adding the lookups and one for removing them.
> 
> The way it's implemented is by modifying the current style of handling
> the lookups a little bit. The per device lookup table is basically
> reverted back to the single linked-list format since it seems that
> these lookups may have to be assigned from several sources.
> 
> Thanks,

Gentle ping on this.

-- 
heikki

  reply	other threads:[~2015-01-08  8:25 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-18  8:23 Heikki Krogerus
2015-01-08  8:25 ` Heikki Krogerus [this message]
2015-01-15  9:21   ` Rafael J. Wysocki
2015-01-14 12:58 ` Linus Walleij
2015-01-14 16:32   ` Darren Hart
2015-01-15  9:28     ` Rafael J. Wysocki
2015-01-15  9:40       ` Heikki Krogerus
2015-01-14 16:32   ` Darren Hart
2015-01-19  5:59   ` Alexandre Courbot
2015-01-19 11:53     ` Heikki Krogerus
2015-01-20 12:16     ` Linus Walleij
2015-01-20 21:25       ` Rafael J. Wysocki
2015-01-22  2:57         ` Alexandre Courbot
2015-01-22 16:14           ` Rafael J. Wysocki
2015-01-23 11:21             ` Heikki Krogerus
2015-01-23 15:14               ` Rafael J. Wysocki
2015-01-26 13:06                 ` Heikki Krogerus
2015-02-10  9:32               ` Alexandre Courbot
2015-02-10 15:10                 ` Rafael J. Wysocki
2015-02-12 12:46                   ` Heikki Krogerus
2015-02-24 20:34           ` David Cohen
2015-02-25  1:34             ` Alexandre Courbot
2015-02-25 18:25               ` David Cohen
2015-03-07 22:13                 ` Linus Walleij
2015-01-22  8:17         ` Linus Walleij
2015-01-22 16:12           ` Rafael J. Wysocki
2015-01-30 14:48             ` Linus Walleij
2015-01-30 16:17               ` Rafael J. Wysocki
2015-02-04  9:51                 ` Linus Walleij
2015-02-04 14:11                   ` Heikki Krogerus
2015-02-10  9:44                     ` Alexandre Courbot
2015-02-12 12:38                       ` Heikki Krogerus

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