On Mon, Mar 23, 2015 at 06:29:11PM +0800, Jean-Christophe PLAGNIOL-VILLARD wrote:

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On Mar 23, 2015, at 6:09 PM, Sascha Hauer [off-list ref] wrote:

On Mon, Mar 23, 2015 at 10:08:27AM +0100, Ludovic Desroches wrote:

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On Mon, Mar 23, 2015 at 07:44:24AM +0100, Sascha Hauer wrote:

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On Fri, Mar 20, 2015 at 04:06:09PM +0100, Ludovic Desroches wrote:

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On Thu, Mar 19, 2015 at 07:56:37PM +0100, Sascha Hauer wrote:

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On Thu, Mar 19, 2015 at 04:39:50PM +0100, Ludovic Desroches wrote:

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	[...]

	pinctrl_defs {
		mci0 {
			mci0_ioset0_1bit_grp {
				at91,pins = <68 69 70>;
				at91,mux = <2>;
			};

			mci0_ioset0_4bit_grp {
				at91,pins = <68 69 70 71 72 73>;
				at91,mux = <2>;
			};

			mci0_ioset0_8bit_grp {
				at91,pins = <68 69 70 71 72 73 74 75 76 77>;
				at91,mux = <2>;
			};
		};
	};

Why are different groups here? Do you want to put them into the dtsi?

We used to have a configuration per pin in our products. On next ones we
will have some constraints ie. on the controller side we still have a
configuration per pin but we will introduced the notion of iosets. This
notion involves that timings are guaranteed only in one ioset. That's
why we can't mix signals from several iosets because. On the controller side
we can do all we want so I would like to use groups as a software protection.

What does happen when you mix signals of different iosets? It won't work
so the developer will change it. What do you need the software
protection for?

I can't say it won't work, it could work in some cases. My fear is to
have some support cases because of this. It seems easy to spot this kind
of issue but experience tell us that we can loose time for this kind of
"stupid" error.

Hm, the software (dts in this case) developer will only mix signals of
different iosets when he is forced to by the board designer. It's the
board designer that has made this mistake, the software developer will
only try to make it work anyway. I doubt that the board designer will
design the board based on the possibilities shown in the dts files.

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- A subnode for these definitions in order to not parse the whole
 pinctrl node to retrieve groups and functions.
- Using node names as function and group names.
- Can we get generic properties to define the groups? Of course a 'pins'
 property is mandatory. In my case I will need an extra one to tell the
 controller how to mux the pins (a same pin can have up to 7 muxing
 possibilities).

Did you have a look at the RFC I sent for these kind of controllers [1] and
the final result for the Mediatek driver currently in Linux-next [2]?.

The binding has both the config and the pins in a single node and thus
is very compact.

Thanks for the links. Well I had a look to them and now I am a bit
lost...

I agree with this binding but it involves to get rid of
pinconf_generic_dt_node_to_map_all, isn't it? What do group and function
become? It seems these concepts have disappeared.

The binding I suggested changes nothing with pinconf, only the pinmux
information is added to the same node. You can still call
pinconf_generic_dt_node_to_map_all() on the nodes, it will simply ignore
the pinmux information. You would have to handle them separately (or
write some generic helper if you like)

Yes, I can still use it. What I mean is there is no generic helper at the
moment to get both pinmux (excepting using the function property) and
pinconf information. Is it planned to have something generic for the
pinmux property?

Not yet, but it would be a good idea to add something generic.

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I see MTK_GET_PIN_NO and MTK_GET_PIN_FUNC macros, on my side,
I think it will feet my needs. Maybe we only need to remove the MTK
prefix and put these macros in another header.

In the mediatek driver, I have also noticed that we have a group for
each pin. I have the feeling that the concept of groups disappear, isn't
it?

This may be because the concept of groups doesn't most hardware.
There really is hardware out there which can only handle the pins in
groups (that is, a single mux switches multiple pins), but this hardware
is not very common. Most hardware can indeed control every pin
indivually. In this situation some drivers are consequent and make a
group out of each pin which renders the group concept moot. Other
drivers just interpret each device node as pin group which creates
artificial groups which do not exist in hardware.

This is what we do on the current pinctrl-at91

It is a bit different with pinctrl-at91, we don't have npins groups.
Even if there is no hardware reality behind we have groups of pins.

and as we do not see the specific of this new IP for at91 it?s difficult to see
if we can use generic or not.

We can use the generic pinconf for sure. My main concern were the
concepts of groups and functions. But it seems, now, we can't get rid of these
concepts.

I am trying to figure out what we loose (or not) if using a mapping such as
'a pin = a group'. For example I am thinking about sysfs, it is probably
more human readable to have some groups with a name related to the
device they are connected as done in pinctrl-at91.

Personally I do prefer when the number of possibility are not high to have a big
soc dtsi.

But in the case of I.MX yes it?s impossible to manage

Best Regards,
J.
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