From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754013AbbANQcq (ORCPT ); Wed, 14 Jan 2015 11:32:46 -0500 Received: from mga01.intel.com ([192.55.52.88]:25315 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753553AbbANQck (ORCPT ); Wed, 14 Jan 2015 11:32:40 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,756,1413270000"; d="scan'208";a="651073738" Message-ID: <54B69A29.6060201@linux.intel.com> Date: Wed, 14 Jan 2015 08:32:41 -0800 From: Darren Hart User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Linus Walleij , Heikki Krogerus , "Rafael J. Wysocki" , Arnd Bergmann CC: Alexandre Courbot , Andy Shevchenko , Mika Westerberg , "linux-gpio@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Ortiz, Samuel" Subject: Re: [RFC PATCH] gpio: support for GPIO forwarding References: <1418890998-23811-1-git-send-email-heikki.krogerus@linux.intel.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ugh, Samuel actually Cc'd this time... On 1/14/15 4:58 AM, Linus Walleij wrote: > On Thu, Dec 18, 2014 at 9:23 AM, 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 >> --- >> >> 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. > > Oh ain't that great. > > So now we start patching around the kernel because the ACPI > tables are erroneous for GPIOs. I'd like some feedback from > Rafael &| Darren on this patch, i.e. if you two think this is a good > way of accounting for bad GPIO descriptions in ACPI tables then > ACK this patch. > > I guess the other option would be to fix up the ACPI DSDT > itself to put resources right, correct? Is this not possible? > > Alexandre also need to ACK it before I dare do anything with > it. > > Do we want to use the same mechanism for augmenting > bad device trees too? > > What I like about it so far is the create/remove symmetry > though. > > Yours, > Linus Walleij > -- Darren Hart Intel Open Source Technology Center