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


On Wed, 22 Mar 2017 16:35:21 +0900
Masanobu SAITOH <> wrote:

>   So what should we do?
>   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.
> I prefer A.

So do I. As you said, not many video drivers use pci_mapreg_map() and
the ones that do can be trivially modified. The driver should decide if
it wants write combining or similar.

have fun

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