Re: [RFC PATCH 0/3] ACPI PCI support for arm64

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Fri, Dec 04, 2015 at 12:11:30AM +0530, Jayachandran C. wrote:
> On Thu, Dec 03, 2015 at 10:56:28AM +0000, Lorenzo Pieralisi wrote:
> > [CC'ing Tomasz]
> > 
> > On Thu, Dec 03, 2015 at 03:54:43AM +0530, Jayachandran C wrote:
> > > This is a very simple and generic implementation of a PCI host controller
> > > based on ACPI. This approach does not pull in the MMCONFIG and ECAM code
> > > from x86.
> > 
> > Why ? Tomasz's patchset does not move MMCONFIG and ECAM code to the generic
> > PCI layer for fun,
> 
> Honestly, Lorenzo, I can see that it was not fun :)

Ok, maybe you have not noticed it was done on Bjorn's request to
consolidate ECAM (ie pulling that code out of x86) instead of reinventing
the wheel for arm64.

> > it is generic code and should be shared by all
> > architectures and most importantly we should not add more churn on
> > top of it which would complicate consolidation even further.
> 
> There is no need for such a common/generic infrastructure to
> walk thru a simple table. In my opinion, trying to do this added
> a lot of complexity into what should be a very simple patchset.
> 
> The x86 code has to deal with a lot more fw/hw issues and I fail
> to see why that mess should be brought into the a new architecture.

See above. We can't keep adding code that does the same thing as
code already in the mainline.

> > > It is important for us to have a working ACPI based PCI host controller
> > > implementation for arm64, so I thought I would post this as a simple
> > > and less disruptive alternative.
> > 
> > It is important for everyone but that's not a reason granting shortcuts.
>  
> I am suggesting a simpler (and maybe better) implementation, which
> is much easier to review and merge - not a shortcut.

You are suggesting adding code to parse the MCFG table, it exists today
and should be consolidated instead of adding on top of it.

> > > This is tested with arm64 QEMU and OVMF. Comments are very welcome.
> > 
> > Tomasz's patch went through several review cycles, please help review
> > it and test it, that's my comment.
> > 
> > A new version should be posted soon, previous version here:
> > 
> > https://lkml.org/lkml/2015/10/27/504
> 
> It seems to be v1, I did not see any ACKs from maintainers either -
> sorry if I am missing something here.

That patchset went through several reviews already, they just reset the
version. I agree with you it is time we got this done, with Tomasz's code,
your code or any combination thereof, please help us get this through,
thanks.

Lorenzo