Re: [PATCH 1/2] spi: bcm2835: add spi-bcm2835aux driver for the auxiliar spi1 and spi2

From: Martin Sperl <kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org>
To: "Noralf Trønnes" <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
Cc: "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"Mark Brown" <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	linux-spi <linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	linux-rpi-kernel
	<linux-rpi-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>,
	"Jakub Kiciński" <moorray3-5tc4TXWwyLM@public.gmane.org>
Subject: Re: [PATCH 1/2] spi: bcm2835: add spi-bcm2835aux driver for the auxiliar spi1 and spi2
Date: Sun, 5 Jul 2015 11:14:59 +1000	[thread overview]
Message-ID: <1400E1A3-43E1-4D0E-A54D-E5D668A4C516@martin.sperl.org> (raw)
In-Reply-To: <55945448.7010502-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>

> On 02.07.2015, at 06:57, Noralf Trønnes <noralf@tronnes.org> wrote:
> 
> 
> Den 01.07.2015 21:39, skrev Martin Sperl:
>>> On 30.06.2015, at 19:42, Mark Brown <broonie@kernel.org> wrote:
>>> 
>>> This looks relevant:
>>> 
>>>>>> On 22.06.2015, at 16:55, Jakub Kiciński <moorray3@wp.pl> wrote:
>>>>>> As mentioned by Noralf UART1 is quite commonly used on Compute Modules.
>>>>>> Proper driver - perhaps modelled as a bus - seems like a prerequisite
>>>>>> for this work.  You are also not using IRQ mux in DT binding example
>>>>>> which is very misleading.
> 
> [...]
> 
>> Finally asking for a recommendation with regards to using a bus
>> to arbitrate access to the enable register there was no feedback
>> how this could be get implemented...
> 
> Maybe you can use drivers/mfd/syscon.c to enable shared access to the
> aux enable register. Then the spi driver could get the regmap with:
> aux_regmap = syscon_regmap_lookup_by_phandle(np, "syscon");

Seems as if you found an answer to my original question of if
there is a framework to handle this.

> About sharing the aux interrupt, could this be implemented in irq-bcm2835
> as a Bank 3?
Obviously it could, but the question is if it is not more overhead than using
a shared interrupt (requesting an interrupt with the shared flag set) in the
first place (like this driver currently does or i2c and USB do).

I am working on a new version to make use of syscon.

Thanks, Martin

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