Re: [PATCH] arch: powerpc: pci-common: fix wrong return value check on phd_id

[Guilherme Piccoli]

On Mon, Jun 18, 2018 at 1:57 PM, Daniel Walker <danielwa@xxxxxxxxx> wrote:
> Cisco has a couple platforms which depend on the domain values getting
> set a certain way. We discovered our machines not detecting the pci
> devices, and traced it back to this commit,
>
> 63a7228 powerpc/pci: Assign fixed PHB number based on device-tree
> properties
>
> It seems that the code is expecting the return value of of_property_read_u64()
> to be the opposite of what it actually is.. It returns zero on success, and a
> negative return value on error. So if you only check when it's non-zero your
> going to set Opal for all platforms but Opal, which I assume is not what was
> expected.

Hi Daniel, thanks for exposing a potential issue and trying to fix.
(And thanks Mauro to point this message, since my email changed).

I disagree with your patch Daniel, I think it's wrong.
Since the logic of my original patch is kind of convoluted, for improve
(even my own) understanding, I tried to over-comment the logic here:
https://pastebin.ubuntu.com/p/4DNvd9b2bY

Please, take a look and see if you agree with the logic now.


Regarding your issue, I'm interested - I think perhaps you have some FW
flaw that might be exposing duplicated "reg" or "ibm,opal-phbid" properties.
Or maybe you somehow rely on the old incremental PHB setting and your
software stack is not working properly with the DT-based PHB values.

Please, elaborate the issue a bit more in order we can try to figure
out. And also, you could try reverting the below two patches and boot
the kernel to be sure it works:

61e8a0d5a02 powerpc/pci: Fix endian bug in fixed PHB numbering
63a72284b15 powerpc/pci: Assign fixed PHB number based on device-tree properties

*Notice* the first is a fix to my patch, and both should be tested together.
Be sure your current kernel has _both or neither_ these patches!

Cheers,


Guilherme