On Fri, Aug 2, 2013 at 10:24 PM, Olof Johansson [off-list ref] wrote:

On Fri, Aug 2, 2013 at 4:06 PM, Christian Daudt [off-list ref] wrote:

quoted

On Fri, Aug 2, 2013 at 1:33 AM, Tony Lindgren [off-list ref] wrote:

quoted

* Jason Cooper [off-list ref] [130731 07:25]:

quoted

So, I'd like to propose we discuss some lessons learned and maybe arrive
at some best practices.  eg, should we just go with mach-$COMPANY/?  How
best to handle config symbols for efficient building?  Deprecation path
for legacy (unconverted) boards?

A lot of that problem goes away by initializing everything as late
as possible, and making things to live under drivers.

One category of items that we haven't found a good place for in this
new multiplatform world is where does dt-driven non-driver code reside
? e.g. we have a secure monitor access function that only kicks in if
the appropriate dt entry is available . It currently resides in
mach-bcm/bcm_kona_smc.c as it seems like the only location for it at
the moment, but that doesn't seem like the best place because (a)
mach-bcm might end up littered with one-of cases like this and (b)
anything in mach-bcm is not visible to arm64 SoCs, and some of those
in the future will need to share with their arm32 cousins.

ARM is working on standardizing some of these interfaces through
things like PSCI. It should take care of _some_ of the SMC needs. I
know you're already shipping some of these platforms though and
firmware interfaces might be locked in to something that's not
PSCI-compatible. :(

Agreed, but that is in the future. Most ARMv7 platforms will likely
never see PSCI and they still need to talk to their secure half. Even
when PSCI code gets into mainline, where will it sit ?

quoted

 But putting in drivers (e.g. drivers/smc) seems like the wrong thing
to do also because this is not a driver.

I really don't think we need to migrate everything to drivers/*. At
some point the need of exorcising code out of arch/arm will reach a
plateu, and there's some code that just simply belongs in that sub
directory.

Ok, that's why I'm trying to determine. How low do we want to go with
the thinning of mach-* dirs.

The sharing with arm64 is the obvious sticky point, since the base
directories aren't the same. Luckily not too many vendors have shipped
arm64 platforms, and nobody is shipping in volume yet, so there's a
little time to sort out some of this.

quoted

 We have a couple of other smallish pieces of IP that just need a bit
of generic init code to keep them happy, which we were discussing
internally where to best land them. At present they are also headed to
mach-bcm.

I think the 3.12 merge window will see the introduction of
drivers/platform/arm. It must not become a dumping ground for
board-file equivalent code though, so I am a little scared to
introduce it. Mostly it should contain whatever glue code isn't
possible or practical to describe with device tree (or ACPI) today,
and in particular for established consumer devices, i.e. for actual
product needs. Compare to what's in drivers/platform/x86 to get a feel
for what we're talking about.

So putting things in drivers/platform solves the a32/a64 sharing
problem at least. So it's a positive step.

quoted

 Ultimately the question is 'what is allowed to reside in mach-<misc>
?' And by extension: 'is there a good home for everything else ?''

Right, and see above about some of my opinions on the matter. arm64
does complicate things quite a bit since it's no longer easy to share
code between the architectures.

Having a few concise examples of what code you're looking for a home
for could be useful for the discussion though. Would you mind
volunteering a few? :)

Other than the already upstreamed SMC code, this again came up in the
context of a dma mux block that we have. The code needs to do static
configuration of the block @ bringup and then there's nothing else for
it to do. We're trying to figure out where the best place for it is.
Options being:
 a) write a couple of functions in arch/arm/mach-bcm/<filename>.c
which based on dt config do the necessary setup
 b) write those same functions with a bit of driver wrapper to make it
pretend to be a driver (i.e. add a probe/remove) and plunk it into
drivers/dma/<filename>.c
 c) ?


 Thanks,
   csd