Re: Allocating Qbus memory space and Qbus map space

[Charles Dickman <chd%chdickman.com@localhost>]

On Fri, Jun 12, 2015 at 10:55 PM, Matt Thomas <matt%3am-software.com@localhost> wrote:
>
>> On Jun 12, 2015, at 7:29 PM, Charles Dickman <chd%chdickman.com@localhost> wrote:
>>
>> I can't find how the kernel handles allocation of Qbus memory space.
>>

>
> There should be an extent for the Q-bus memory in bus_dma_tag_t for
> that q-bus (_sgmap->aps_ex).
>
> Use it with
>
> extent_alloc_region(dmat->_sgmap->aps_ex, vastart, vaend, EX_WAITOK);

OK That's what I did.

> Thinking about this, bus_space_map on the iot should allocate the same
> address region from the sgmap.  That it does not is a bug.

Then what I was looking for wasn't there but should be.

> Or the uba attach code should probe each page and if does
> not timeout, mark it as mappable.

Am I correct that now there are two extents that are covering the same
resource, but they are not coordinated? bus_space_map covers the Q22
address space including the I/O space. dmat->_sqmap->aps_ex covers the
Qbus map. Properly done, the uba bus_space should only include the
memory that exists in real devices and the rest of the address space
given to the DMA map.