[PATCH 01/16] ARM: dts: exynos4210: Replace legacy GPIO bank nodes with pinctrl bank nodes

* Stephen Warren [off-list ref] [121010 09:36]:

On 10/10/2012 01:26 AM, Linus Walleij wrote:

quoted

On Mon, Oct 8, 2012 at 10:39 AM, Tomasz Figa [off-list ref] wrote:

quoted

Seuqential patches from this series introduce SoC-specific data parsing
from device tree.

This patch removes legacy GPIO bank nodes from exynos4210.dtsi and
replaces them with nodes and properties required for these patches.

So to be clear:

quoted

+       pinctrl-bank-types {
+               bank_off: bank-off {
+                       samsung,reg-names = "func", "dat", "pud",
+                                               "drv", "conpdn", "pudpdn";
+                       samsung,reg-params = <0x00 4>, <0x04 1>, <0x08 2>,
+                                               <0x0C 2>, <0x10 2>, <0x14 2>;
+               };

This is starting to look like a firmware language, I have mixed
feelings about this. Shall this be read:

"Poke 4 into 0x00, poke 1 into 0x04, poke 2 into 0x08" etc?

We really need to discuss this, Grant has already NACK:ed
such approaches once.

Well, I don't think he NACK'd Tony Lindgren's generic pinctrl driver,
which is doing this exact same thing. I did raise the same point about
Tony's driver when he posted it, but nobody seemed inclined to NACK it
based on that at the time, IIRC...

To summarize, using reg value pairs in DT makes sense if the amount
of data is huge. Otherwise we'll be describing indidual hardware bits
as properties in DT, or have to have huge amounts of static data in
the kernel.

Where it does not make sense is if there's a sequence of reads
and writes with test loops in between.. But that's does not look
to be the case here.

The reg value pairs will be readable when the DT preprocessing is
available, and that allows the values to be orred together while
DT properties don't. The alternative is to describe hardware register
bits as DT properties, which is very bloated.

But considering all this.. Are the samsung,reg-names really needed
by the kernel?

The pinctrl named modes actually are more generic from the pinctrl
client driver point of view as you can set up multiple states for
runtime PM.
 

BTW, the idea here is IIRC to create a generic Samsung pinctrl driver
that works across N different Samsung SoCs, each with different register
layout, without having to encode the register layout into tables in the
kernel.

quoted

If you're still going to do this, it is mandatory
to NOT use magic hex numbers anymore, because Stephen has
merged preprocessor support to the DTC compiler so you
can use #defined macros.

See commit:
cd296721a9645f9f28800a072490fa15458d1fb7

That feature isn't enabled yet. While dtc has been modified to be able
to accept input that's been generated/processed by cpp, there is still
ongoing discussion about how/whether to actually enable *.dts to use
that feature.

Hey finally! That's good news.

Regards,

Tony