Re: PCI BAR's prefetchable bit and pci_mapreg_map()

[Michael <macallan%netbsd.org@localhost>]

Hello,

On Wed, 22 Mar 2017 16:35:21 +0900
Masanobu SAITOH <msaitoh%execsw.org@localhost> wrote:

>   A) modify pci_mapreg_map(). Stop setting BUS_SPACE_MAP_PREFETCHABLE
>      by defalut when prefetchable bit is set. If a driver really know
>      the whole area of the BAR is prefetchable, set BUS_SPACE_MAP_PREFETCHABLE
>      in the 4th argument(busflags) of pci_mapreg_map(). pci_mapreg_map()
>      check for both the 4th argument and the prefetchable bit, it sets
>      BUS_SPACE_MAP_PREFETCHABLE only when both bits are set.

On 2nd thought, I think we should ignore the prefetchable bit in the
BAR here and just go with whatever the driver wants, since you ran into
devices which have the bit set and shouldn't, and I have seen graphics
chips which don't set it for their video memory apertures.

have fun
Michael