[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-ppc] [Qemu-devel] [PATCH v2 10/14] pci: allow 0 address for PC
From: |
Peter Maydell |
Subject: |
Re: [Qemu-ppc] [Qemu-devel] [PATCH v2 10/14] pci: allow 0 address for PCI IO regions |
Date: |
Tue, 10 Dec 2013 22:14:18 +0000 |
On 10 December 2013 21:42, Michael Roth <address@hidden> wrote:
> Quoting Peter Maydell (2013-12-05 17:33:48)
>> And presumably whoever put that specific check for 0 into
>> QEMU had a reason for it.
>>
>> On the other hand I can't now find whatever document it was
>> that I was reading that claimed 0 wasn't valid :-(
>
> Can't seem to find anything either, checked the 2.3 spec as well. I tried to
> look up the git history for the new_addr == 0 check but unfortunately it
> seemed
> to be part of the initial check-in.
>
> The only clue I've found regarding special-casing for a 0-bar is this:
>
> "Power-up software can determine how much address space the device requires by
> writing a value of all 1's to the register and then reading the value back.
> The
> device will return 0's in all don't-care address bits, effectively specifying
> the address space required. Unimplemented Base Address registers are hardwired
> to zero." - PCI 3.0, 6.2.5.1
Googling again brought up this mailing list thread:
http://www.pcisig.com/reflector/msg00459.html
which includes what is supposedly a quote from the PCI 2.1 spec:
# "Note: A Base Address register does not contain a valid
# address when it is equal to "0""
(I don't have access to the 2.1 version to check.)
This text seems to have been removed from the 2.2 spec.
thanks
-- PMM
- [Qemu-ppc] [PATCH v2 05/14] spapr_pci: add get/set-power-level RTAS interfaces, (continued)
- [Qemu-ppc] [PATCH v2 05/14] spapr_pci: add get/set-power-level RTAS interfaces, Michael Roth, 2013/12/05
- [Qemu-ppc] [PATCH v2 07/14] spapr_pci: add ibm, configure-connector RTAS interface, Michael Roth, 2013/12/05
- [Qemu-ppc] [PATCH v2 06/14] spapr_pci: add get-sensor-state RTAS interface, Michael Roth, 2013/12/05
- [Qemu-ppc] [PATCH v2 03/14] spapr: add helper to retrieve a PHB/device DrcEntry, Michael Roth, 2013/12/05
- [Qemu-ppc] [PATCH v2 02/14] spapr_pci: populate DRC dt entries for PHBs, Michael Roth, 2013/12/05
- [Qemu-ppc] [PATCH v2 09/14] pci: make pci_bar useable outside pci.c, Michael Roth, 2013/12/05
- [Qemu-ppc] [PATCH v2 10/14] pci: allow 0 address for PCI IO regions, Michael Roth, 2013/12/05
- Re: [Qemu-ppc] [PATCH v2 10/14] pci: allow 0 address for PCI IO regions, Michael S. Tsirkin, 2013/12/12
[Qemu-ppc] [PATCH v2 08/14] memory: add memory_region_find_subregion, Michael Roth, 2013/12/05
[Qemu-ppc] [PATCH v2 11/14] spapr_pci: enable basic hotplug operations, Michael Roth, 2013/12/05
[Qemu-ppc] [PATCH v2 14/14] spapr_pci: emit hotplug add/remove events during hotplug, Michael Roth, 2013/12/05
[Qemu-ppc] [PATCH v2 13/14] spapr_events: event-scan RTAS interface, Michael Roth, 2013/12/05
[Qemu-ppc] [PATCH v2 12/14] spapr_events: re-use EPOW event infrastructure for hotplug events, Michael Roth, 2013/12/05