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

On Mon, Dec 14, 2020 at 4:43 AM Daniel Thompson
[off-list ref] wrote:

On Fri, Dec 11, 2020 at 05:05:58PM +0000, Daniel Thompson wrote:

quoted

On Fri, Dec 11, 2020 at 08:37:40AM -0600, Rob Herring wrote:

quoted

On Fri, Dec 11, 2020 at 6:15 AM Daniel Thompson

quoted

    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?

I think I'd just go the adding a delay route. It's a fairly big series
and depends on my other clean-up done in 5.10. And there's at least
some possibility it regresses some platform given the limited testing
linux-next gets.

Rob

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