[RFC PATCH 2/2] arm: pcibios: move to generic PCI domains

[Liviu Dudau]

On Mon, Nov 03, 2014 at 11:26:25PM +0000, Simon Horman wrote:
> On Fri, Oct 31, 2014 at 05:04:49PM +0000, Phil Edworthy wrote:
> > Hi Bjorn,
> > 
> > On 31 October 2014 16:37, Bjorn wrote:
> > > On Fri, Oct 31, 2014 at 7:43 AM, Phil Edworthy
> > > <phil.edworthy at renesas.com> wrote:
> > > > Hi Lorenzo,
> > > >
> > > > On 30 October 2014 11:45, Lorenzo wrote:
> > > >> Most if not all ARM PCI host controller device drivers either ignore the
> > > >> domain field in the pci_sys_data structure or just increment it every
> > > >> time a host controller is probed, using it as a domain counter.
> > > >>
> > > >> Therefore, instead of relying on pci_sys_data to stash the domain number
> > > >> in a standard location, ARM pcibios code can be moved to the newly
> > > >> introduced generic PCI domains code, implemented in commits:
> > > >>
> > > >> commit 41e5c0f81d3e676d671d96a0a1fafb27abfbd9
> > > >> ("of/pci: Add pci_get_new_domain_nr() and of_get_pci_domain_nr()")
> > > >>
> > > >> commit 670ba0c8883b576d0aec28bd7a838358a4be1
> > > >> ("PCI: Add generic domain handling")
> > > >>
> > > >> In order to assign a domain number dynamically, the ARM pcibios defines
> > > >> the function, called by core PCI code:
> > > >>
> > > >> void pci_bus_assign_domain_nr(...)
> > > >>
> > > >> that relies on a DT property to define the domain number or falls back to
> > > >> a counter; its usage replaces the current domain assignment code in PCI
> > > >> host controllers present in the kernel.
> > > >>
> > > >> Cc: Arnd Bergmann <arnd at arndb.de>
> > > >> Cc: Phil Edworthy <phil.edworthy at renesas.com>
> > > >> Cc: Jason Gunthorpe <jgunthorpe at obsidianresearch.com>
> > > >> Cc: Jingoo Han <jg1.han at samsung.com>
> > > >> Cc: Bjorn Helgaas <bhelgaas at google.com>
> > > >> Cc: Russell King <linux at arm.linux.org.uk>
> > > >> Cc: Mohit Kumar <mohit.kumar at st.com>
> > > >> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> > > >
> > > > This patch fixes a current problem with R-Car devices where there is an
> > > > internal PCI bridge and an external PCIe bridge on the devices. Both drivers
> > > > work independently but need to be on different domains. Just needed to
> > > enable
> > > > PCI_DOMAINS along with this.
> > > > I've done basic testing that the internal PCI and external PCIe work at the
> > > > same time.
> > > 
> > > Hi Phil,
> > > 
> > > Thanks for testing this.  Can you give me some more guidance on where
> > > you'd like to see this merged?  Until your comment about this fixing a
> > > current problem on R-Car, I probably would have considered this to be
> > > a cleanup and enhancement and hence material for v3.19.  But if R-Car
> > > is actually broken and this fixes it, maybe this should go in for
> > > v3.18 instead.
> > I don’t think its urgent as most of our customers use LTSI kernels, e.g. v3.10.
> > Renesas typically provide out-of-tree BSPs with upstream code back ported, along
> > with other patches. Simon Horman (Renesas maintainer, cc'd) generally handles
> > the back ports, so I'll defer to his opinion.
> 
> Hi Phil,
> 
> from my point of view it would be best if this went into -stable if it is a
> fix. However, as you point out, from a customer point of view it shouldn't
> be a big deal as they should get backports via our LTSI kernel regardless of
> if the patch goes through stable or not.

Unfortunately this patch depends on a series that only got in in v3.18-rc1, so
I don't think -stable is a workable target.

Best regards,
Liviu

> 
> > > If it is currently broken, is there a point where it broke?  I assume
> > > it used to work at one time.  If there's a commit that broke it, it
> > > would be nice to reference that in the changelog and explain exactly
> > > what was broken and how this fixes it.
> > Both the internal PCI and external PCIe drivers work on their own, but have
> > never worked at the same time. I think it was just unfortunate timing when I
> > added the PCIe driver. At that time, the internal PCI driver didn’t have the
> > relevant DT nodes for the board I was using so I didn't see any conflicts.
> > 
> > Thanks
> > Phil
> 

-- 
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