linux-kernel - Re: [PATCH 2/2] Make non-linear GPIO ranges accesible from gpiolib

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Date:	Tue, 25 Jun 2013 17:47:14 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Christian Ruppert <christian.ruppert@...lis.com>,
	Patrice CHOTARD <patrice.chotard@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>,
	Sascha Leuenberger <sascha.leuenberger@...lis.com>,
	Pierrick Hascoet <pierrick.hascoet@...lis.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Alexandre Courbot <acourbot@...dia.com>
Subject: Re: [PATCH 2/2] Make non-linear GPIO ranges accesible from gpiolib

On Tue, Jun 25, 2013 at 5:31 PM, Stephen Warren <swarren@...dotorg.org> wrote:
> On 06/25/2013 08:56 AM, Linus Walleij wrote:
>> On Fri, Jun 21, 2013 at 11:17 PM, Stephen Warren <swarren@...dotorg.org> wrote:
>>> On 06/20/2013 05:57 AM, Christian Ruppert wrote:
>>
>>>> Your remark seems to reflect one of the following two hardware
>>>> architectures:
>>>>
>>>>                                                      +- SPI
>>>>                  Physical pins --- GPIO --- pinctrl -+- I2C
>>>>                                                      +- mmc
>>>
>>> (that's diagram 1)
>>>
>>>>
>>>>                                 +- GPIO
>>>>                  Physical pins -+           +- SPI
>>>>                                 +- pinctrl -+- I2C
>>>>                                             +- mmc
>>>
>>> (that's diagram 2)
>>>
>>>> TB10x hardware architecture:
>>>>
>>>>                                             +- SPI
>>>>                  Physical pins --- pinctrl -+- I2C
>>>>                                             +- mmc
>>>>                                             +- GPIO
>>>
>>> (that's diagram 3)
>>>
>>> No, I was thinking of diagram 3 above. I'm not sure if diagrams (1) or
>>> (2) are common or exist?
>>
>> The U300 pin controller is obviously of type (1) as it can spy on
>> the signals.
>
> U300 HW might be diagram (1) - I can't say since I'm not familiar with
> the HW. However, the fact that GPIO can spy on signals in no way at all
> implies that the HW must conform to diagram (1).

That's true. And I don't know what it actually is in this case.
That hardware is actually weird in many ways, thanks to
helpful HW engineers modeling use cases into the HW.

>> The Nomadik pin controller is basically type (2).

This I know however to be true, as I have access to the
low-level schematics of the ASIC.

Yours,
Linus Walleij
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