linux-kernel - Re: [PATCH v2 2/5] mfd: ts4800-syscon: add driver for TS-4800 syscon

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Date:	Tue, 3 Nov 2015 08:38:17 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	Damien Riegel <damien.riegel@...oirfairelinux.com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-watchdog@...r.kernel.org, shawnguo@...nel.org,
	kernel@...gutronix.de, wim@...ana.be, robh+dt@...nel.org,
	sameo@...ux.intel.com, dinh.linux@...il.com, linux@...ck-us.net,
	kernel@...oirfairelinux.com, arnd@...db.de
Subject: Re: [PATCH v2 2/5] mfd: ts4800-syscon: add driver for TS-4800 syscon

On Mon, 02 Nov 2015, Damien Riegel wrote:
> On Mon, Nov 02, 2015 at 09:12:53AM +0000, Lee Jones wrote:
> > [Cc'ing Arnd]
> > 
> > On Fri, 30 Oct 2015, Damien Riegel wrote:
> > > On Fri, Oct 30, 2015 at 05:56:56PM +0000, Lee Jones wrote:
> > > > On Thu, 29 Oct 2015, Damien Riegel wrote:
> > > > 
> > > > > Driver for TS-4800 syscon. These registers belong to a FPGA that is
> > > > > memory mapped and are used for counters, enable various IPs in the FPGA,
> > > > > control LEDs, control IOs, etc.
> > > > > 
> > > > > Currently, only the watchdog is handled.
> > > > 
> > > > Why do you require your own syscon driver?
> > > > 
> > > > What's wrong with the generic one?
> > > > 
> > > 
> > > The generic one uses a regmap_config with reg_stride set to 4 and val_bits
> > > to 32.
> > > 
> > > TS-4800 syscon registers are 16-bit wide and must be accessed with 16
> > > bit read and writes:
> > > http://wiki.embeddedarm.com/wiki/TS-4800#Syscon
> > > 
> > > I will address the other issues in the next version (split commit,
> > > license issue, style, and superfluous remove).
> > 
> > The Syscon driver was written to be generic so that each
> > vendor/platform didn't require their own incarnation.  How unique is
> > the TS-4800?
> > 
> > Perhaps it might be better to supply a generic 16 bit Syscon for
> > devices akin to the TS-4800?
> 
> The TS-4800 syscon could use a generic 16-bit syscon. There is nothing
> specific that requires a driver besides that.
> 
> We could add some optional properties to the generic syscon node to
> configure reg_bits, val_bits, and reg_stride (and pad_bits ?). Would
> that be a good solution ?

Without looking at the ramifications of such an addition, the premise
sounds good to me.  So long as the current behaviour remains the
default.

> > Arnd, any opinion on this?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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