Date:	Mon, 21 Jun 2010 17:45:14 +0200
From:	Luotao Fu <l.fu@...gutronix.de>
To:	Rabin VINCENT <rabin.vincent@...ricsson.com>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	STEricsson_nomadik_linux <STEricsson_nomadik_linux@...t.st.com>,
	Linus WALLEIJ <linus.walleij@...ricsson.com>,
	"l.fu@...gutronix.de" <l.fu@...gutronix.de>
Subject: Re: [PATCH 1/3] mfd: add STMPExxxx I/O Expander support

On Mon, Jun 21, 2010 at 07:03:07PM +0530, Rabin VINCENT wrote:
> On Sat, Jun 19, 2010 at 01:42:24 +0200, Samuel Ortiz wrote:
> > On Mon, May 31, 2010 at 05:47:14PM +0530, Rabin Vincent wrote:
> > > Add support for the STMPExxxx family of I/O Expanders from
> > > STMicroelectronics.  These devices include upto 24 gpios, a PWM
> > > controller, and a keypad controller.  This patch adds the MFD core.
> > The patchset looks fairly good, but before merging it I'd like to know of we
> > could merge it with this one:
> > https://patchwork.kernel.org/patch/106173/
> > 
> > I don't know enough about the hardware, and although the register layouts don't
> > look like they have much in common, I'd like to know from the actual HW
> > manufacturer (i.e. you :)) if there's something we can do here.
> 
> I don't have any inside information about these parts (we just use them
> on our U8500 dev boards), but all the datasheets are publicly
> available[1].  There seems to be more than a dozen variants of this MFD
> with varying combinations of devices.
> 
> [1] http://www.st.com/stonline/stappl/productcatalog/app?path=/pages/stcom/PcStComPartNumberSearch.searchPartNumber&search=stmpe
> 
> On Sat, Jun 19, 2010 at 15:50:16 +0200, Luotao Fu wrote:
> > hmm, I took a quick look into the core driver. The register layout
> > seems, as Samuel mentioned, quite different. However, the r/w
> > functionalities and irq handling are quite the same. For now I'd say
> > that should be possible to merge the stuff.
> 
> The IRQ handling and GPIO block seem to be about the same (registers are
> at different offsets, but this is also the case between STMPE1601 and
> STMPE24XX and is thus already handled in the STMPExxxx driver).  The
> STMPExxxx GPIO driver should also already be able to handle a variant
> with lesser gpios, such as STMPE811.
> 
> Similarities:
>  - I2C access functions
>  - GPIO block (same registers, different offsets)
>  - IRQ block (same registers and handling, different irqs and different
>    register offsets)
> 
> Differences:
>  - Different blocks (but sharing between different groups of variants)
>  - SYSCTRL register bits (reset, clock enabling)
>  - GPIO altfunc bits
>  - The STMPE811 also has a SPI interface, while most other support only I2C
>    This is also not avaiabile in Luotao's driver so I'm not addressing
>    this for now.
> 
I2C is the most common usage variant. Otherwise adding spi access
routines should be no big deal. Some additional to the probe function
might be needed besides the r/w core functions. I do think that we leave
the stuff this way and take care of them if somebody does need SPI.

> Here's a preliminary patch (untested!) which shows how the STMPExxx can
> be made more generic to support 811 and hopefully other variants.  If
> this looks sane, I'll complete it up, fold it in, and repost the
> STMPExxxx series for review and also 811 testing and touchscreen
> addition from Luotao.
> 

I'll test the patch as soon as I can. Do you have any public GIT tree
with the stmpexxx stuffs in them, so that I might be able to merge it
with my board stuffs directly?

cheers
Luotao Fu

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