linux-kernel - Re: [PATCH v3 1/1] i2c: add ACPI support for I2C mux ports

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Message-ID: <20151021085241.GA5949@cumulusnetworks.com>
Date:	Wed, 21 Oct 2015 01:52:41 -0700
From:	Dustin Byford <dustin@...ulusnetworks.com>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	rjw@...ysocki.net, andriy.shevchenko@...ux.intel.com
Subject: Re: [PATCH v3 1/1] i2c: add ACPI support for I2C mux ports

On Wed Oct 21 11:34, Mika Westerberg wrote:
> On Wed, Oct 21, 2015 at 01:21:16AM -0700, Dustin Byford wrote:
> > On Wed Oct 21 11:12, Mika Westerberg wrote:
> > > On Tue, Oct 20, 2015 at 10:49:59AM -0700, Dustin Byford wrote:
> > > > I considered it, but I thought a default that fairly closely matches the
> > > > old behavior was more convenient.
> > > > 
> > > > On the other hand, leaving it up to the controllers makes it all very
> > > > explicit and perhaps simpler to reason about.
> > > > 
> > > > 
> > > > I could be convinced either way.  But, if we move it to the controller
> > > > drivers, which ones need the change?
> > > > 
> > > > grep -i acpi drivers/i2c/busses/i2c*
> > > > 
> > > > shows 18 drivers that might care.
> > > 
> > > I'm quite confident the designware I2C is enough for now. Intel uses it
> > > for all SoCs with LPSS and I think AMD has the same block for their I2C
> > > solution.
> > 
> > I certainly care about i801, ismt, and isch.  Doesn't this affect any
> > i2c controller with clients that may be enumerated through ACPI?
> 
> Yes, but so far I haven't seen any other devices being used for this
> than the I2C designware.
> 
> Which hardware you are testing this patch on?

I'm working with a number of x86-based network switch platforms.  Mostly
rangeley at the moment, but I'm sure others are in the works.  Have a
look at:

http://www.opencompute.org/wiki/Networking/SpecsAndDesigns

for examples.


My goal, hence the recent patches, is to help the network switch
industry move a lot of platform description into ACPI.  That means lots
of complicated I2C trees; switches are full of I2C devices.

		--Dustin
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