linux-kernel - Re: [PATCH V2 5/6] dt: Document Tegra20/30 pinctrl binding

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Date:	Thu, 22 Mar 2012 09:45:31 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Dong Aisheng <aisheng.dong@...escale.com>
CC:	Dong Aisheng-B29396 <B29396@...escale.com>,
	"linus.walleij@...aro.org" <linus.walleij@...aro.org>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linus.walleij@...ricsson.com" <linus.walleij@...ricsson.com>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"dongas86@...il.com" <dongas86@...il.com>,
	"shawn.guo@...aro.org" <shawn.guo@...aro.org>,
	"thomas.abraham@...aro.org" <thomas.abraham@...aro.org>,
	"tony@...mide.com" <tony@...mide.com>,
	"sjg@...omium.org" <sjg@...omium.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH V2 5/6] dt: Document Tegra20/30 pinctrl binding

On 03/21/2012 10:00 PM, Dong Aisheng wrote:
> On Wed, Mar 21, 2012 at 11:57:14PM +0800, Stephen Warren wrote:
>> On 03/21/2012 03:19 AM, Dong Aisheng wrote:
>>> On Wed, Mar 21, 2012 at 01:44:38AM +0800, Stephen Warren wrote:
>>>> Define a new binding for the Tegra pin controller, which is capable of
>>>> defining all aspects of desired pin multiplexing and pin configuration.
>>>> This is all based on the new common pinctrl bindings.
>>>>
>>>> Add Tegra30 binding based on Tegra20 binding.
...
>>>> +Example board file extract:
>>>> +
>>>> +	pinctrl@...00000 {
>>>> +		sdmmc4_default: pinmux {
>>>> +			sdmmc4_clk_pcc4 {
>>>> +				nvidia,pins =	"sdmmc4_clk_pcc4",
>>>> +						"sdmmc4_rst_n_pcc3";
>>>> +				nvidia,function = "sdmmc4";
>>>> +				nvidia,pull = <0>;
>>>> +				nvidia,tristate = <0>;
>>>> +			};
>>>> +			sdmmc4_dat0_paa0 {
>>>> +				nvidia,pins =	"sdmmc4_dat0_paa0",
>>>> +						"sdmmc4_dat1_paa1",
>>>> +						"sdmmc4_dat2_paa2",
>>>> +						"sdmmc4_dat3_paa3",
>>>> +						"sdmmc4_dat4_paa4",
>>>> +						"sdmmc4_dat5_paa5",
>>>> +						"sdmmc4_dat6_paa6",
>>>> +						"sdmmc4_dat7_paa7";
>>>> +				nvidia,function = "sdmmc4";
>>>> +				nvidia,pull = <2>;
>>>> +				nvidia,tristate = <0>;
>>>
>>> It seems it does not support per pin config for tegra30 and we have to
>>> separate them in different nodes with same group config value, right?
>>
>> Sorry, I don't understand the question.
>
> I meant for tegra, the config(not mux) in one pinctrl node functions
> on all entities in nvidia,pins, IOW, all pin or group must have the
> same config.
> So we can not set them differently in one node.
> 
> For example, considering if  sdmmc4_dat0_paa0 is nvidia,pull <0>
> while sdmmc4_dat1_paa1 is nvidia,pull <1>.
> Then we need to separate them in different pinctrl nodes, right?

Yes, that's true.

However, note that you can have more than one node affecting a
particular pin or group if you want. For example, you could have one set
of nodes that sets the mux, another set of nodes that sets
pullup/down/none, another set that sets tristate/driven. That way,
within each set of nodes, you get to group together all pins with
similar properties. This is all because we take the list of affected
pins/groups from the nvidia,pins property, rather than e.g. the node
name, so it's possible to list the same pin/group in multiple nodes. An
example from the Tegra Harmony board file:

There's one node for each mux function that's used, specifying which
pins/groups it's used on:

    ata {
            pins = "ata";
            function = "ide";
    };
    atb {
            nvidia,pins = "atb", "gma", "gme";
            nvidia,function = "sdio4";
    };
    ... many other nodes for other functions

There's also one node for each combination of pull and tristate that's
used, specifying which pins/groups it's used on:

    conf_ata {
            nvidia,pins = "ata", "atb", "atc", "atd", "ate",
                    "cdev1", "dap1", "dtb", "gma", "gmb",
                    "gmc", "gmd", "gme", "gpu7", "gpv",
                    "i2cp", "pta", "rm", "slxa", "slxk",
                    "spia", "spib";
            nvidia,pull = <0>;
            nvidia,tristate = <0>;
    };
    ... many other nodes for other pull/tristate combinations

I ran a script to group the various pins into nodes in different ways,
and this particular combination seemed to generate the smallest device
tree source file for Harmony.
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