• Brent Casavant's avatar
    [PATCH] ioc4: Core driver rewrite · 22329b51
    Brent Casavant authored
    This series of patches reworks the configuration and internal structure
    of the SGI IOC4 I/O controller device drivers.
    These changes are motivated by several factors:
    - The IOC4 chip PCI resources are of mixed use between functions (i.e.
      multiple functions are handled in the same address range, sometimes
      within the same register), muddling resource ownership and initialization
      issues.  Centralizing this ownership in a core driver is desirable.
    - The IOC4 chip implements multiple functions (serial, IDE, others not
      yet implemented in the mainline kernel) but is not a multifunction
      PCI device.  In order to properly handle device addition and removal
      as well as module insertion and deletion, an intermediary IOC4-specific
      driver layer is needed to handle these operations cleanly.
    - All IOC4 drivers are currently enabled by a single CONFIG value.  As
      not all systems need all IOC4 functions, it is desireable to enable
      these drivers independently.
    - The current IOC4 core driver will trigger loading of all function-level
      drivers, as it makes direct calls to them.  This situation should be
      reversed (i.e. function-level drivers cause loading of core driver)
      in order to maintain a clear and least-surprise driver loading model.
    - IOC4 hardware design necessitates some driver-level dependency on
      the PCI bus clock speed.  Current code assumes a 66MHz bus, but the
      speed should be autodetected and appropriate compensation taken.
    This patch series effects the above changes by a newly and better designed
    IOC4 core driver with which the function-level drivers can register and
    deregister themselves upon module insertion/removal.  By tracking these
    modules, device addition/removal is also handled properly.  PCI resource
    management and ownership issues are centralized in this core driver, and
    IOC4-wide configuration actions such as bus speed detection are also
    handled in this core driver.
    This patch:
    The SGI IOC4 I/O controller chip implements multiple functions, though it is
    not a multi-function PCI device.  Additionally, various PCI resources of the
    IOC4 are shared by multiple hardware functions, and thus resource ownership by
    driver is not clearly delineated.  Due to the current driver design, all core
    and subordinate drivers must be loaded, or none, which is undesirable if not
    all IOC4 hardware features are being used.
    This patch reorganizes the IOC4 drivers so that the core driver provides a
    subdriver registration service.  Through appropriate callbacks the subdrivers
    can now handle device addition and removal, as well as module insertion and
    deletion (though the IOC4 IDE driver requires further work before module
    deletion will work).  The core driver now takes care of allocating PCI
    resources and data which must be shared between subdrivers, to clearly
    delineate module ownership of these items.
    Signed-off-by: default avatarBrent Casavant <bcasavan@sgi.com>
    Acked-by: default avatarPat Gefre <pfg@sgi.com>
    Acked-by: default avatarJeremy Higdon <jeremy@sgi.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>