Re: [PATCH v2 0/2] pinctrl: Intel Cherryview/Braswell support

From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Timur Tabi <timur@codeaurora.org>
Cc: Linus Walleij <linus.walleij@linaro.org>,
	Alexandre Courbot <gnurou@gmail.com>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Mathias Nyman <mathias.nyman@linux.intel.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Ning Li <ning.li@intel.com>, Alan Cox <alan@linux.intel.com>,
	lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 0/2] pinctrl: Intel Cherryview/Braswell support
Date: Tue, 4 Nov 2014 11:39:07 +0200	[thread overview]
Message-ID: <20141104093907.GH1618@lahna.fi.intel.com> (raw)
In-Reply-To: <20141104082056.GG1618@lahna.fi.intel.com>

On Tue, Nov 04, 2014 at 10:20:56AM +0200, Mika Westerberg wrote:
> On Mon, Nov 03, 2014 at 05:24:55PM -0600, Timur Tabi wrote:
> > On Mon, Nov 3, 2014 at 5:01 AM, Mika Westerberg
> > <mika.westerberg@linux.intel.com> wrote:
> > > Hi,
> > >
> > > This is second version of the patch series adding pinctrl/GPIO support
> > > for Intel Braswell and Cherrryview. The previous version can be found here:
> > >
> > > https://lkml.org/lkml/2014/10/27/118
> > >
> > > I've dropped patches [2/4] and [3/4] as they are already applied to the
> > > pinctrl tree.
> > 
> > Mika,
> > 
> > I am also trying to add ACPI enablement to my pinctrl driver (not yet
> > submitted), but I'm new to ACPI and pin control drivers, so I have a
> > lot of catching up to do.
> > 
> > In reviewing this patchset, it appears to me that pinctrl-cherryview.c
> > is a normal pinctrl driver that has an acpi_match_table entry, and
> > nothing more.
> 
> Indeed, it just a normal platform driver that can be enumerated from
> ACPI using the .acpi_match_table entry.
> 
> > Assuming that this driver is booting on an ACPI system, what is the
> > mechanism that calls into the driver to configure the pins?  Is there
> > a definition for pin control in ASL that provides similar
> > functionality as the pinctrl nodes in a device tree?
> 
> There is nothing like that yet in ACPI world but with the ACPI _DSD
> patches we are getting properties similar to DT which means that we can
> provide pinctrl bindings from ACPI systems as well. Typically it has
> been the BIOS that configures things but it cannot get everything 100%
> right.
> 
> Currently I've been testing the muxing functionality so that I have a
> small board file that sets mappings and the driver core handles
> everything from there. For example I have development board where SPI
> pins are muxed as GPIOs by the BIOS and with the mappings when the SPI
> device appears the core will mux SPI out of those pins.

For reference the latest ACPI _DSD patches can be found here

https://lkml.org/lkml/2014/10/21/762