---
- branch: MAIN
  date: Mon Dec  2 17:13:13 UTC 2019
  files:
  - new: '1.39'
    old: '1.38'
    path: src/sys/dev/pci/pci_map.c
    pathrev: src/sys/dev/pci/pci_map.c@1.39
    type: modified
  id: 20191202T171313Z.bae3e13f80a4b6d534810c91fba4d5f037506531
  log: |
    Leave it entirely up to the driver whether to map prefetchable.

    We have only a few drivers that pass BUS_SPACE_MAP_PREFETCHABLE to
    pci_mapreg_map -- dev/pci/if_hme_pci.c, dev/pci/igma.c,
    dev/pci/radeonfb.c, dev/pci/wcfb.c -- and they all do it for ROM or
    framebuffers.

    Based on a subthread from macallan@ in the earlier discussion:

    https://mail-index.NetBSD.org/tech-kern/2017/03/23/msg021685.html

    The thrust is that:
    - a driver not asking for prefetchable mappings shouldn't get it
    - some devices are correctly used with prefetchable mappings, but for
      some reason fail to set the prefetchable bit in the BAR
    - nobody could identify any classes of device for which
      (a) the driver asks for prefetchable mappings, but
      (b) certain matching devices can't actually be used with
          prefetchable mappings

    This brings pci_mapreg_map in line with what the documentation says;
    the documentation never advertised that the prefetchable bit in the
    BAR could cause the bus_space mapping to be prefetchable.
  module: src
  subject: 'CVS commit: src/sys/dev/pci'
  unixtime: '1575306793'
  user: riastradh