On Friday 07 December 2012, Michal Simek wrote:

On 12/06/2012 10:27 PM, Bjorn Helgaas wrote:

quoted

[+cc linux-pci]

On Thu, Dec 6, 2012 at 7:23 AM, Michal Simek [off-list ref] wrote:

quoted

Hi guys,

I have a question regarding to sharing generic OF pcie driver between
two architectures MB and ARM Zynq.
Is drivers/pci/pcie location good for it?
Make no sense to have the same driver in two locations.

I think you're talking about a PCI host bridge driver.  It would
definitely be nice to move toward a generic, shared driver.  Host
bridge drivers are responsible for enumerating the PCI hierarchy below
the bridge.  Enumeration is not really PCIe-specific, so I wouldn't
put it in drivers/pci/pcie.

Not a PCI expert, just trying to find out the proper location for this shared driver.

I'd suggest creating a drivers/pci/host directory. We will have more of
these in the future. AFAIK, there is no fully generic (architecture
independent) way to interface a PCI host driver to the PCI subsystem,
but I think we are getting closer to that. You are probably fairly
free to modify the microblaze architecture specific code though if needed.

quoted

quoted

Is using readl/writel IO functions in this driver the best option
which we can have?
Or is there any other recommendation?

I'm not really a driver person, but if you're writing a new driver,
wouldn't you use the iomap interfaces (ioremap(), ioread32(), etc)
rather than readl()?

That driver exists but it is not in mainline and it is better to directly
add it to proper location with correct io functions.
The question is if ioread/iowrite functions are correct one.
PowerPC io-defs.h suggests that readl/writel should be used for PCI.

ioread32/iowrite32 are defined to behave the same way readl/writel regarding
addressing modes and barriers, but also allow operating on __iomem pointers
that were returned from ioport_map(). You probably don't need that.

Some architectures like powerpc have their own accessors for on-chip MMIO
areas, but ARM does not. The PowerPC rule is that you must use either
readl/writel or ioread32/iowrite32 to access devices connected to a PCI
bus, but you would not necessarily do that for the PCI host controller
itself on PowerPC.

	Arnd

	Arnd