[SLOF] [PATCH] Correctly set ibm,my-drc-index

[David Gibson]

On Mon, Sep 14, 2015 at 08:07:33AM +0200, Thomas Huth wrote:
> On 14/09/15 05:57, David Gibson wrote:
> > On Sun, 13 Sep 2015 21:25:17 -0500
> > Michael Roth <mdroth at linux.vnet.ibm.com> wrote:
> > 
> >> Quoting David Gibson (2015-09-13 18:45:00)
> >>> On Fri, 11 Sep 2015 18:48:19 +0200
> >>> Laurent Vivier <lvivier at redhat.com> wrote:
> >>>
> >>>> The current calculation of DRC index for PCI card doesn't take
> >>>> into account the PHB bridge index, so with several bridges we
> >>>> can have several devices with the same DRC index.
> >>>>
> >>>> This is a problem when we want to unplug a PCI card with
> >>>> drmgr which is based on the DRC index.
> >>>>
> >>>> Signed-off-by: Laurent Vivier <lvivier at redhat.com>
> >>>
> >>> Actually, I think the safer fix is just for SLOF not to touch the
> >>> ibm,my-drc-index property if it's already present.  QEMU is already
> >>> setting it correctly, and SLOF is overwriting it  :(.
> >>
> >> This patch makes sense and fixes a real bug, but my understanding is that
> >> SLOF only fills in properties missing from device node rather than
> >> overwriting ones provided by QEMU. On my end, on the second PHB, I see
> >> this for a hotplugged device in slot 1 (where prop comes from QEMU via
> >> RTAS):
> >>
> >> mdroth at ubuntu:/proc/device-tree/pci at 800000020000001/pci at 2$ od -x
> >> ibm,my-drc-index
> >> 0000000 0140 1000
> >> 0000004
> >>
> >> And after reboot (where prop comes from QEMU via SLOF):
> >>
> >> mdroth at ubuntu:/proc/device-tree/pci at 800000020000001/ethernet at 2$ od -x
> >> ibm,my-drc-index
> >> 0000000 0140 1000
> >> 0000004
> >>
> >> If you're getting the buggy values (0040 1000, i.e. 40000010 be32 value)
> >> it makes me think you're not using the QEMU-generated DTs for device
> >> nodes. Older SLOF that doesn't have Nikunj's updates possibly? I think
> >> in that case values might get overwritten/thrown out.
> > 
> > 
> > Ah.  Good point, yes, the downstream qemu doesn't have the code to set
> > my-drc-index.
> > 
> > So the question is, do we fix this in SLOF, or do we pull down the qemu
> > changes to move more device node creation into qemu, making it moot.
> 
> If the code in SLOF is wrong, I'd say the fix should be include in SLOF
> anyway. slof/fs/pci-properties.fs is the "common" PCI setup code, so
> this fix might come in handy for board-js2x (or maybe any future other
> board) as well.

Except that the DRC indexes are PAPR specific, so they certainly won't
be relevant on js2x and very unlikely they'd be relevant for anything
else in future.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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