linux-kernel - Re: [RFC v2 25/39] pcmcia: add HAS

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Date:   Wed, 4 May 2022 13:38:35 +0100 (BST)
From:   "Maciej W. Rozycki" <macro@...am.me.uk>
To:     Arnd Bergmann <arnd@...nel.org>
cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        Dominik Brodowski <linux@...inikbrodowski.net>
Subject: Re: [RFC v2 25/39] pcmcia: add HAS_IOPORT dependencies

On Wed, 4 May 2022, Arnd Bergmann wrote:

> Almost all architectures that support CONFIG_PCI also provide
> HAS_IOPORT today (at least at compile time, if not at runtime),
> with s390 as a notable exception. Any machines that have legacy
> PCI device support will also have I/O ports because a lot of
> legacy PCI cards used it, and any machine with a pc-card slot
> should also support legacy PCI devices.
> 
> If we get new architectures without I/O space in the future, they
> would certainly not care about supporting old cardbus devices.

 POWER9 is another architecture with no port I/O space[1]:

Table 3-2. PCIe TLP command summary
-----------+-----------------------------+-------------------------------
  Class    |           Type Name         |           Notes
===========+=============================+===============================
Completion | Completion without Data     | For PCI CFG Writes (nonposted)
           |                             | or for error responses.
Completion | Completion with Data        | CI load responses.
Nonposted  | Configuration Read Request  | Outbound only.
Nonposted  | Configuration Write Request | Outbound only.
Posted     | Message Request             | Inbound only.
Nonposted  | Memory Read Request         |
Posted     | Memory Write Request        |
===========+=============================+===============================
 1. All other valid PCIe command types are ignored and dropped.
 2. Invalid PCIe request command types will result in a completion
    response of Unsupported Request.
------------------------------------+------------------------------------

that we do support -- I have such a system.  And I guess POWER10 is the 
same, as will be all future architecture updates.

References:

[1] "Power Systems Host Bridge 4 (PHB4) Specification", Version 1.0, 
    International Business Machines Corporation, 27 July 2018, Section 3.1 
    "PHB4 Command Details", p.29

  Maciej