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From: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: "Jean-Christophe PLAGNIOL-VILLARD" <plagnioj@jcrosoft.com>,
	"Linus Walleij" <linus.walleij@linaro.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Heiko Stübner" <heiko@sntech.de>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	alan.cheng@mediatek.com, "Russell King" <linux@arm.linux.org.uk>,
	"Hongzhou Yang" <hongzhou.yang@mediatek.com>,
	toby.liu@mediatek.com, "Grant Likely" <grant.likely@linaro.org>,
	"Joe.C" <yingjoe.chen@mediatek.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"Vladimir Murzin" <vladimir.murzin@arm.com>,
	"Pawel Moll" <pawel.moll@arm.com>,
	"Ian Campbell" <ijc+devicetree@hellion.org.uk>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Matthias Brugger" <matthias.bgg@gmail.com>,
	dandan.he@mediatek.com, "huang eddie" <eddie.huang@mediatek.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Ashwin Chaugule" <ashwin.chaugule@linaro.org>,
	"Sascha Hauer" <kernel@pengutronix.de>,
	"Kumar Gala" <galak@codeaurora.org>
Subject: Re: [PATCH v3 2/3] dt-bindings: Add pinctrl bindings for mt65xx/mt81xx.
Date: Wed, 14 Jan 2015 00:24:53 +0800	[thread overview]
Message-ID: <15A74798-690D-40CA-88F0-A2CA06781546@jcrosoft.com> (raw)
In-Reply-To: <20150113161614.GF23940@pengutronix.de>


> On Jan 14, 2015, at 12:16 AM, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> 
> On Tue, Jan 13, 2015 at 11:05:22AM +0100, Linus Walleij wrote:
>>>> I am worried that there is something in your reasoning that sort of
>>>> assumes all pin controllers mux pins one-by-one and not in groups.
>>>> How do we make it impossible to write a device tree that also
>>>> make hardware that do groupwise config viable without ambiguities?
>>> 
>>> Sorry, I don't understand this sentence. What do you mean here?
>>> 
>>> The bindings I suggested are for individual pin based controllers
>>> only. I know there are group based controllers, but I don't want to
>>> change their bindings. I believe there is no single binding that is
>>> good for both types of controllers.
>>> 
>>> I think we must face it that individual pin based controllers are
>>> different from group based controllers. That's the main difference
>>> between different pin controllers and I think there are good reasons
>>> to reflect that in the device tree.
>> 
>> OK let's work on a binding for this usecase.
> 
> Okay.
> 
>> 
>>> You often talk about ambiguities. Could you give an example what
>>> ambiguities you mean?
>> 
>> What happened was this pins = ; arguments were sometimes
>> strings and sometimes integers, that becomes strange to handle
>> in code, ambiguous.
> 
> I see. I like naming it 'pinmux' because that's what it is: pins and
> mux settings. A plain 'pinno' suggests that it contains only pin mubers,
> without mux setting. How about 'pin-no-mux'? We also could add an
> explicit "pins-are-numbered" property instead of distinguishing this
> by property names.
> 
>> 
>> I'm fuzzily referring to the concept of things being named the
>> same way in different device trees, yet lacking commonality,
>> confusing a human reader that they may be the same thing,
>> even if it is possible to write schemas and parsers handling
>> it unambigously, so not ambiguity in the formal logic sense.
>> 
>> If i later want to refactor the code around this to a central
>> parser I cannot do so because it would lead to formal ambiguities
>> and is non-doable.
> 
> There could be a flag in the pinctroller struct indicating whether the
> properties are to be interpreted as strings or as numbers.
> 
>> 
>>> Note that the way we combine pin/mux in a single define is not new,
>>> the i.MX pin controller uses this already and so far I'm not aware of
>>> any problems this makes.
>> 
>> Yeah we never had time to sit down and come up with proper
>> generic pin control bindings, we went with custom bindings
>> partly because of general disagreements, partly because I
>> was new to device tree and honestly had no idea of how
>> to skin this cat.
>> 
>> Now that we get to formalize generic bindings for DT and
>> ACPI and whatever alike, I prefer if we make both groupwise
>> and per-pin pin controllers as strict and well defined as
>> possible.
>> 
>> One minor problem I have with using an integer for mux config
>> is that it assumes something about how many pins, configs etc
>> that may exist on such a system. This should be stated
>> explicitly in the bindings atleast so we know what restrictions
>> we build into them. String-based function+group matching has
>> no such restrictions.
> 
> No problem, that can be documented. Normally the defines should be used
> anyway, not the plain pin numbers.
> 
> BTW one thing I really like about integers is the pure binary size. In
> barebox I also parse the pinmux settings from the device tree. The
> drivers using string matching are multiple times bigger due to the
> string tables:
> 
> -rw-r--r-- 1 sha ptx  5436 Jan 13 15:00 imx-iomux-v3.o
> -rw-r--r-- 1 sha ptx 42060 Jan 13 15:00 pinctrl-tegra30.o

Agreed with Sascha that’s why I chose integer for at91 too

if you want string just use define instead to make it more readable

Best Regards,
J.
> 
> Sascha
> 
> -- 
> Pengutronix e.K.                           |                             |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
> Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
> Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel


  reply	other threads:[~2015-01-13 18:53 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1415709535-31515-1-git-send-email-hongzhou.yang@mediatek.com>
2014-11-18 16:24 ` [PATCH v3 0/3] Add Mediatek SoC Pinctrl/GPIO driver for MT8135 Sascha Hauer
     [not found] ` <1415709535-31515-3-git-send-email-hongzhou.yang@mediatek.com>
2014-11-27  8:44   ` [PATCH v3 2/3] dt-bindings: Add pinctrl bindings for mt65xx/mt81xx Linus Walleij
2014-11-27 10:18     ` Sascha Hauer
2014-11-28 16:12       ` Linus Walleij
2014-12-02 13:55         ` Sascha Hauer
2015-01-10 21:33           ` Linus Walleij
2015-01-12 12:22             ` Sascha Hauer
2015-01-13 10:05               ` Linus Walleij
2015-01-13 16:16                 ` Sascha Hauer
2015-01-13 16:24                   ` Jean-Christophe PLAGNIOL-VILLARD [this message]
2015-01-16  9:53                   ` Linus Walleij
2015-01-16 10:23                     ` Yingjoe Chen
2015-01-20  9:45                       ` Linus Walleij
2015-01-26 15:57                         ` Sascha Hauer
2015-01-27 14:07                           ` Linus Walleij
     [not found] ` <1415709535-31515-2-git-send-email-hongzhou.yang@mediatek.com>
2014-11-27  9:14   ` [PATCH v3 1/3] ARM: mediatek: Add Pinctrl/GPIO driver for mt8135 Linus Walleij

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