Date: Fri, 28 Aug 2015 10:35:50 -0700 From: John Baldwin <jhb@freebsd.org> To: freebsd-arch@freebsd.org Cc: Marcel Moolenaar <marcel@xcllnt.net>, Justin Hibbits <jrh29@alumni.cwru.edu> Subject: Re: Devices with 36-bit paddr on 32-bit system Message-ID: <1568331.OrSoeYfXsf@ralph.baldwin.cx> In-Reply-To: <ED4B5B25-D7A7-440C-9452-4C79B0800D2E@xcllnt.net> References: <CAHSQbTDsvB32%2BLyzHJO78VwUwAfUTMOUQp13BMCUpapSMT0fbg@mail.gmail.com> <ED4B5B25-D7A7-440C-9452-4C79B0800D2E@xcllnt.net>
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On Tuesday, August 25, 2015 08:55:45 AM Marcel Moolenaar wrote: >=20 > > On Aug 24, 2015, at 11:44 PM, Justin Hibbits <jrh29@alumni.cwru.edu= > wrote: > >=20 > > With my work porting FreeBSD to PowerPC e500mc and e5500, I have > > devices in my device tree mapped well above the 4GB mark > > (0xffexxxxxx), and have no idea how to properly address them for > > resources in rman. Do we already have a solution to support this? > > Part of the problem is the powerpc nexus does a straight convert to= > > vm_offset_t of rman_get_start() (itself returning a u_long), and > > vm_offset_t is not necessarily equal to vm_paddr_t (on Book-E power= pc > > vm_offset_t is 32-bits, vm_paddr_t is 64-bits). >=20 > I think the best solution is to represent a resource address > space with a type other than u_long. It makes sense to have > it use bus_addr_t or vm_paddr_t for example. Such a change > comes at a high price for sure, but you=E2=80=99ll fix it once and > for all. I don=E2=80=99t think you should kluge your way out of this.= .. Expanding beyond u_long is the right solution. PAE doesn't generally s= uffer from this on i386 (though the ram0 device "punts" and ignores RAM range= s above 4G as a workaround). However, u_long is baked into the bus resource API quite a bit. Specif= ically, the values 0ul and ~0ul are used as magic numbers in lots of places to = request "anywhere" locations. Some of this has been mitigated by bus_alloc_resource_any(), but that doesn't cover all cases. You will p= robably want to add some explicit constants and do a sweep replacing the magic = numbers with those first (and MFC the constants at least to make it easier to p= ort drivers across branches). Then you can change the type. As far as the best type: rman's are in theory generic and not just for = bus addresses. I'd be tempted to let each platform define an rman_addr_t a= long with RMAN_ADDR_MAX constants, but in practice it is probably fine to us= e bus_addr_t and BUS_SPACE_MAXADDR. If you do that it also means you can= skip the step of having to MFC new constants. Note that various bus APIs will have to change to use bus_addr_t instea= d of u_long as well. --=20 John Baldwin
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