[RFC HACK PATCH] PCI: dwc: layerscape: Hack around enumeration problems with Honeycomb LX2K

[Daniel Thompson]

On Fri, Dec 11, 2020 at 05:05:58PM +0000, Daniel Thompson wrote:
> On Fri, Dec 11, 2020 at 08:37:40AM -0600, Rob Herring wrote:
> > On Fri, Dec 11, 2020 at 6:15 AM Daniel Thompson
> > >     BTW I noticed many other pcie-designware drivers take advantage
> > >     of a function called dw_pcie_wait_for_link() in their init paths...
> > >     but my naive attempts to add it to the layerscape driver results
> > >     in non-booting systems so I haven't embarrassed myself by including
> > >     that in the patch!
> > 
> > You need to look at what's pending for v5.11, because I reworked this
> > to be more unified. The ordering of init is also possibly changed. The
> > sequence is now like this:
> > 
> >         dw_pcie_setup_rc(pp);
> >         dw_pcie_msi_init(pp);
> > 
> >         if (!dw_pcie_link_up(pci) && pci->ops->start_link) {
> >                 ret = pci->ops->start_link(pci);
> >                 if (ret)
> >                         goto err_free_msi;
> >         }
> > 
> >         /* Ignore errors, the link may come up later */
> >         dw_pcie_wait_for_link(pci);
> 
> Thanks. That looks likely to fix it since IIUC dw_pcie_wait_for_link()
> will end up waiting somewhat like the double check I added to
> ls_pcie_link_up().
> 
> I'll take a look at let you know.

Yes. These changes have fixed the enumeration problems for me.

I tested pci/next and I cherry picked your patch series onto v5.10 and
both are working well.

Given this fixes a bug for me, do you think there is any scope for me
to whittle down your series into patches for the stable kernels or am
I likely to find too many extra bits being pulled in?


Daniel.