linux-kernel - Re: Adding interrupt support to gpio-ich driver (possibly via SCI)

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Message-ID: <53436B1C.8010102@roeck-us.net>
Date:	Mon, 07 Apr 2014 20:21:00 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Matthew Garrett <mjg59@...f.ucam.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Peter Tyser <ptyser@...-inc.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: Adding interrupt support to gpio-ich driver (possibly via SCI)

On 04/07/2014 07:48 PM, Matthew Garrett wrote:
> On Fri, Apr 04, 2014 at 09:25:50AM -0700, Guenter Roeck wrote:
>
>> Is there a clean way to use any of those to implement interrupt support
>> for this driver ? I thought about hijacking the SCI interrupt by registering
>> an interrupt handler with acpi_install_sci_handler(), but that would restrict
>> the driver to kernel only (or the acpi function would have to be exported),
>> and I have no idea if it would work or, more importantly, if it would be
>> the best approach to solve the problem, or if the result would be acceptable.
>> I can figure out the "working" part, but that would not help much if I would
>> have to carry the patch locally because it is not acceptable for upstream
>> integration.
>
> You shouldn't need to install an SCI handler - the way the hardware will
> generate an SCI is to raise a GPE. If you know which GPE the device
> raises (my recollection is that for most Intel chipsets it's GPIO number
> + 0x10) then you can just call acpi_install_gpe_handler(). The problem

Sounds good. Do you by any chance have a pointer to some documentation
explaining this in some more detail ?

> is that the firmware may well already be using some of those GPIOs, and
> there's no easy way to tell. Checking the interrupt configuration isn't
> sufficient, since some of them may just be used as outputs.
>
The gpio-ich driver already has some magic to detect that condition - I
noticed that I can not request all GPIO pins on all hardware. Either case,
the gpio pins I am interested in are well defined on the hardware I am
dealing with, so I can be sure I won't step on some unexpected use.

Thanks!

Guenter

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