linux-kernel - Re: Sharing PCIE driver between Microblaze and Arm zynq

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Date:	Fri, 07 Dec 2012 10:45:01 +0100
From:	Michal Simek <monstr@...str.eu>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	Michal Simek <michal.simek@...inx.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	linux-arch@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
	Grant Likely <grant.likely@...retlab.ca>,
	John Linn <John.Linn@...inx.com>,
	John Williams <jwilliams@...inx.com>, linux-pci@...r.kernel.org
Subject: Re: Sharing PCIE driver between Microblaze and Arm zynq

On 12/06/2012 10:27 PM, Bjorn Helgaas wrote:
> [+cc linux-pci]
>
> On Thu, Dec 6, 2012 at 7:23 AM, Michal Simek <michal.simek@...inx.com> wrote:
>> 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.


>> 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.


>> Also just want to check if it is correct to use pcie device_type.
>
> I don't know what you're asking here.  Can you elaborate or give a
> specific example?

If node property device_type pcie should be used.
device_type = "pcie";

For pci it is device_type = "pci";
For network it is device_type = "network"
the same for serial, watchdogs.

Do we have any list of device_types which we should use?

Thanks,
Michal

-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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