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

Thomas Huth thuth at redhat.com
Mon Sep 14 16:07:33 AEST 2015

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.


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