linux-kernel - Re: [PATCH V6 2/5] PCI: Adapt pci_register_io_range() for indirect-IO and PCI I/O translation

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Date:   Mon, 30 Jan 2017 18:10:30 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "zhichang.yuan" <yuanzhichang@...ilicon.com>
Cc:     catalin.marinas@....com, will.deacon@....com, robh+dt@...nel.org,
        frowand.list@...il.com, bhelgaas@...gle.com, rafael@...nel.org,
        mark.rutland@....com, brian.starkey@....com, olof@...om.net,
        arnd@...db.de, linux-arm-kernel@...ts.infradead.org,
        lorenzo.pieralisi@....com, benh@...nel.crashing.org,
        linux-kernel@...r.kernel.org, linuxarm@...wei.com,
        devicetree@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-serial@...r.kernel.org, minyard@....org, liviu.dudau@....com,
        zourongrong@...il.com, john.garry@...wei.com,
        gabriele.paoloni@...wei.com, zhichang.yuan02@...il.com,
        kantyzc@....com, xuwei5@...ilicon.com
Subject: Re: [PATCH V6 2/5] PCI: Adapt pci_register_io_range() for
 indirect-IO and  PCI I/O translation

On Tue, Jan 24, 2017 at 03:05:22PM +0800, zhichang.yuan wrote:
> After indirect-IO is introduced, system must can assigned indirect-IO devices
> with logical I/O ranges which are different from those for PCI I/O devices.
> Otherwise, I/O accessors can't identify whether the I/O port is for memory
> mapped I/O or indirect-IO.

Maybe:

  We must assign logical I/O port space for indirect I/O such that the
  I/O accessors can tell whether a logical I/O port refers to memory-
  mapped I/O space or indirect I/O space.

> As current helper, pci_register_io_range(), is used for PCI I/O ranges
> registration and translation, indirect-IO devices should also apply these
> helpers to manage the I/O ranges. It will be easy to ensure the assigned
> logical I/O ranges unique.
> But for indirect-IO devices, there is no cpu address. The current
> pci_register_io_range() can not work for this case.
> 
> This patch makes some changes on the pci_register_io_range() to support the
> I/O range registration with device's fwnode also. After this, the indirect-IO
> devices can register the device-local I/O range to system logical I/O and
> easily perform the translation between device-local I/O range and sytem
> logical I/O range.

> -int __weak pci_register_io_range(phys_addr_t addr, resource_size_t size)
> +int __weak pci_register_io_range(struct fwnode_handle *node, phys_addr_t addr,
> +				 resource_size_t size, unsigned long *port)

Why is this __weak?  It looks like it's been __weak since its
introduction by 41f8bba7f555 ("of/pci: Add pci_register_io_range() and
pci_pio_to_address()"), but I don't see any other implementations of
it.

Can you add a patch that does nothing but make this non-weak?

> +#else
> +	/*
> +	 * powerpc and microblaze have their own registration,
> +	 * just look up the value here

Can you include a pointer to the powerpc and microblaze registration
code here?  It's conceivable that somebody could generalize this
enough to support powerpc and microblaze as well.

> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -34,6 +34,9 @@
>  
>  #include <linux/pci_ids.h>
>  
> +/* the macro below flags an invalid cpu address
> + * and is used by IO special hosts              */

s/cpu/CPU/

Use conventional multi-line comment style:

/*
 * IO_RANGE_IOEXT flags an invalid CPU address ...
 */

> +#define IO_RANGE_IOEXT (resource_size_t)(-1ull)

And put this close to related things, e.g., pci_register_io_range(),
instead of just dropping it in at the top of the file.

>  /*
>   * The PCI interface treats multi-function devices as independent
>   * devices.  The slot/function address of each device is encoded
> @@ -1197,8 +1200,8 @@ int __must_check pci_bus_alloc_resource(struct pci_bus *bus,
>  						  resource_size_t),
>  			void *alignf_data);
>  
> -
> -int pci_register_io_range(phys_addr_t addr, resource_size_t size);
> +int pci_register_io_range(struct fwnode_handle *node, phys_addr_t addr,
> +			  resource_size_t size, unsigned long *port);
>  unsigned long pci_address_to_pio(phys_addr_t addr);
>  phys_addr_t pci_pio_to_address(unsigned long pio);
>  int pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr);
> -- 
> 1.9.1
>