[PATCH 3/4] arm64: add support for i.MX8M EVK board

Am Donnerstag, den 25.01.2018, 21:03 +0800 schrieb Dong Aisheng:

On 2018-01-25 19:09, Lucas Stach wrote:

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Am Donnerstag, den 25.01.2018, 18:49 +0800 schrieb Dong Aisheng:

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On 2018-01-25 18:31, Lucas Stach wrote:

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Am Donnerstag, den 25.01.2018, 18:10 +0800 schrieb?
aisheng.dong at codeaurora.org:

[...]

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AFAIK we switched to generic pinconfig since MX7ULP as
maintainer?

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won't
access old binding pinctrl drivers.

I'm not convinced that the generic pinconf is good fit. For
pingroups
with different configs for some of the pins, like the example
above, we
would need to split things into multiple DT nodes. This really
hurts
readability, so I'm not going to switch to the generic stuff
without
some really convincing arguments.

Per my understanding, based on the last discussion with Linus W,
we?
actually did this in order to increase the readability that 1)
user?
does
not need?to see the 'ugly' unreadable raw data and refer to
reference
manual 2)?unified generic binding format which already exist in
kernel
and used by many platforms.

Actually MXS platform already used it for many years in a similar
way.
So IMHO a little hurt to add another node for different pad
setting?
in?
the same group won't be enough reason to stop switching to
generic?
config.

Does it make sense?

I know that Linus W is pushing for this common pinconf thing in the
name of readability. It's just that I don't think it's such a clear
win.

After all you still need to look into the reference manual or
binding
to see which values in the common binding correspond to a specific
drive/pull strength, etc.

User don't need to look into reference manual and they don't need to
compose the 'ulgy' raw data which is the most tough thing.

With generic binding, it probably can saving ~80% pad setting effort
by refer to the defined generic config properties.
And things can be even better when the reference code is already
there
as user becomes know which property supported.

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On the other hand it really bloats the DT description of the pin
configuration. If you want to look at an (IMHO) bad example, go
look at
the Tegra DTs. The Tegra pincontrol implements the "separate
properties
for each pinconf option" that is pushed by Linus W. This bloated
the DT
description to the point that no-one is able/willing to write those
descriptions anymore and the only viable way to get them is to
auto-
generate them from some spreadsheets. Not really what I would call
an
readable...

I wonder the worst case you're worrying whether exist in reality.
Take imx6qdl-sabresd as an example, about half of pingroups having
the?
same
pad setting while others have two different settings at most.
That means it may not bloat the device tree too much.

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Maybe I'm a little stubborn when it comes to this topic, but at
Pengutronix we see a lot of customer designs where we need to come
up
with the board DT. Bloating each one of those and making the work
of
the developers harder in the name of a readability win that I just
don't see doesn't sound like something I want to support. :)

Hmm.. In contrast, what i feel currently is that it may ease the
using?of pad setting, not make it harder. Not sure if i overlooked
something.

Let's listen to Shawn and Linus W if they have some comments.

While I'm still unconvinced that the generic binding actually adds any
value, I'll go and see how converting the MX8M pinctrl will look on a
real board.

This will delay rev 2 of this series a bit, but I hope to have
something to send out tomorrow.

Regards,
Lucas