1. 21 Jun, 2005 1 commit
    • 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: Pat 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>
      22329b51