linux-kernel - Re: [PATCH 1/3] pinctrl: pinctrl-imx: add imx pinctrl core driver

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Message-ID: <20120415144549.GJ3852@pengutronix.de>
Date:	Sun, 15 Apr 2012 16:45:49 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Shawn Guo <shawn.guo@...aro.org>
Cc:	Dong Aisheng <dongas86@...il.com>, linus.walleij@...ricsson.com,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	rob.herring@...xeda.com, kernel@...gutronix.de,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/3] pinctrl: pinctrl-imx: add imx pinctrl core driver

On Sun, Apr 15, 2012 at 10:17:43PM +0800, Shawn Guo wrote:
> On Sun, Apr 15, 2012 at 11:49:04AM +0800, Dong Aisheng wrote:
> ...
> > My plan is:
> > 1) not all combinations, just define frequently used ones since
> > it's hard to define all combinations groups for per based IMX.
> > (maybe we can try to add a fix-up function which can do minor changes
> > based on available ones, then user does not need to write a new group
> > caused by only a small change.
> > what do you think?)
> > 
> > 2)  When dt supports macro, will try convert string to integer macro.
> > Then it maybe:
> > fsl,pins = <MX6Q_PAD_SD4_CMD 0
> >                 MX6Q_PAD_SD4_CLK 0
> >                 MX6Q_PAD_SD4_DAT0 1
> >                 .................>,
> > Why i did not start pin id with a raw integer is because it's less
> > meaning to user and
> > not easy to read in dts file.
> > 
> We may want to use integer from the beginning to reduce the churn on
> driver later.
> 
> I'm thinking about documenting the definition we used to have in
> iomux-mx*.h in the binding document and assign id to each of them
> in order.
> 
> pinmux						id
> ------						--
> MX6Q_PAD_SD2_DAT1__USDHC2_DAT1			0
> MX6Q_PAD_SD2_DAT1__ECSPI5_SS0			1
> MX6Q_PAD_SD2_DAT1__WEIM_WEIM_CS_2		2
> ...
> 
> The ordering between the list and imx6q_pin_regs[] array need to match.
> 
> By looking at the binding document, we can just put pinmux-id into
> property "fsl,pins" (maybe rename it to "fsl,pinmux-ids") to get the
> desired pinmux settings.  With doing so, we can gain the following.
> 
> 1) The pinmux-id can be used as index to locate the entry in array
>    imx6q_pin_regs[], so that the slow string lookup can be avoid.
> 
> 2) Property "fsl,mux" can be dropped, as it's been encoded in
>    imx6q_pin_regs[] entry.
> 
> 3) Converting the existing board files to device tree will be much
>    easier.  We only need to find the pinmux-id of those existing
>    definitions and put them in "fsl, pinmux-ids".
> 
> 4) When DTC support macro, we can simply move the pinmux-id list from
>    binding document into dts file.  No driver change is needed at all.
> 
> Thoughts?

I like it. I think it will feel much more natural to use.

Sascha

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