linux-kernel - Re: [PATCH v7 3/3] arm64: Add architecture support for PCI

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Message-ID: <20140319172140.GA16328@e106497-lin.cambridge.arm.com>
Date:	Wed, 19 Mar 2014 17:21:41 +0000
From:	Liviu Dudau <Liviu.Dudau@....com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	linux-pci <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Will Deacon <Will.Deacon@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>,
	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>
Subject: Re: [PATCH v7 3/3] arm64: Add architecture support for PCI

On Wed, Mar 19, 2014 at 01:56:19PM +0000, Catalin Marinas wrote:
> On Mon, Mar 17, 2014 at 06:05:25PM +0000, Liviu Dudau wrote:
> > On Mon, Mar 17, 2014 at 05:38:21PM +0000, Catalin Marinas wrote:
> > > On Fri, Mar 14, 2014 at 06:05:27PM +0000, Liviu Dudau wrote:
> > > > On Fri, Mar 14, 2014 at 05:38:08PM +0000, Arnd Bergmann wrote:
> > > > > On Friday 14 March 2014, Catalin Marinas wrote:
> > > > > > On Fri, Mar 14, 2014 at 03:34:18PM +0000, Liviu Dudau wrote:
> > > > > > > --- /dev/null
> > > > > > > +++ b/arch/arm64/kernel/pci.c
> > > > > > [...]
> > > > > > > +int pci_register_io_range(phys_addr_t address, resource_size_t size)
> > > > > > [...]
> > > > > > > +unsigned long pci_address_to_pio(phys_addr_t address)
> > > > > > [...]
> > > > > > > +void pcibios_fixup_bus(struct pci_bus *bus)
> > > > > > [ actually most of this file ]
> > > > > > 
> > > > > > Maybe it was raised before already but can we have __weak generic
> > > > > > definitions of these functions? They don't seem to be arm64 specific in
> > > > > > any way.
> > > [...]
> > > > Catalin, if you are happy to ask for ACKs from all arch maintainers that might get
> > > > affected by our custom version of pci_address_to_pio() before you can pull PCI support
> > > > for arm64 then I can propose a new patchset.
> > > 
> > > You don't need to change the other architectures, that's the point of a
> > > __weak definition, it will be automatically overridden. If you want, you
> > > can even place a GENERIC_PCI or whatever config option that is only
> > > selected by arm64 for the time being.
> > 
> > pci_address_to_pio() is alread __weak. My patch was adding the arm64 version of it. Adding
> > an #ifdef GENERIC_PCI to the __weak implementation is not just a temporary solution.
> 
> Ah, I start to understand what you mean, pci_address_to_pio() is already
> defined as __weak in drivers/of/address.c. So the reason we redefine it
> on arm64 is that it uses the io_list resources which are populated by
> pci_register_io_range(). Do you see any other architecture using a
> similar logic (that could be shared)?

All architectures that memory map the PCI IO range should be supported by my version of
pci_address_to_pio(). But that still leaves the x86 and those architectures that have
separate IO space or map it 1:1 into CPU address space to carry a different version (which
the current "generic" weak version catters for).

> 
> Any other functions in this file that could be shared (and are not
> __weak already)?

A version of the pci_register_io_range() that uses part of pci_ioremap_io() (the calculation
of io_offset part).

My ultimate point is that no matter how long we argue about the shape of the functions that
I've added into arch/arm64/kernel/pci.c I don't think we can get away without having that
file, or at least not in the first phase if we want speedy integration into mainline.

Best regards,
Liviu

> 
> -- 
> Catalin

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

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