Re: [PATCH] PCI: Disable RRS polling for Intel SSDPE2KX020T8 nvme

[Bjorn Helgaas <helgaas@kernel.org>]

Nirmal, Jonathan, can you confirm that when RRS SV is enabled for VMD
Root Ports, we should actually see the 0x0001 value when a device
downstream of VMD responds with RRS?  From the log below, it appears
that we actually get 0xffffffff when reading Device ID after a reset.

On Thu, Aug 21, 2025 at 11:39:36AM -0500, Bjorn Helgaas wrote:
> On Thu, Jul 03, 2025 at 08:05:05AM +0800, Hui Wang wrote:
> > On 7/2/25 17:43, Hui Wang wrote:
> > > On 7/2/25 07:23, Bjorn Helgaas wrote:
> ...

> > > > Thank you!  It seems like we get 0xffffffff (probably PCIe error) for
> > > > a long time after we think the device should be able to respond with
> > > > RRS.
> > > > 
> > > > I always thought the spec required that after the delays, a device
> > > > should respond with RRS if it's not ready, but now I guess I'm not
> > > > 100% sure.  Maybe it's allowed to just do nothing, which would lead to
> > > > the Root Port timing out and logging an Unsupported Request error.
> > > > 
> > > > Can I trouble you to try the patch below?  I think we might have to
> > > > start explicitly checking for that error.  That probably would require
> > > > some setup to enable the error, check for it, and clear it.  I hacked
> > > > in some of that here, but ultimately some of it should go elsewhere.
> ...

The patch is here:
https://lore.kernel.org/r/20250701232341.GA1859056@bhelgaas
and the log with that patch is here:

> > This is the testing result and log.
> > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2111521/comments/65

> We're waiting for 01:00.0, and we're seeing the poll message for about
> 375 ms:

[   10.177356] pci 10000:00:02.0: PCI bridge to [bus 01]
[   10.182278] pci 10000:01:00.0: [8086:0a54] type 00 class 0x010802 PCIe Endpoint
[   10.195247] pci 10000:00:02.0: pci_reset_secondary_bus: PCI_BRIDGE_CTL_BUS_RESET deasserted
[   10.195464] pci 10000:00:02.0: waiting 100 ms for downstream link, after activation
[   10.195467] pci 10000:00:02.0: pcie_wait_for_link_delay: active 1 delay 100 link_active_reporting 1
[   10.229269] pci 10000:00:02.0: pcie_wait_for_link_status: LNKSTA 0xb043
[   10.334784] pci 10000:00:02.0: pcie_wait_for_link_delay: waited 100ms

>   [   10.334786] pci 10000:01:00.0: pci_dev_wait: VF- bus reset timeout 59900
>   [   10.334792] pci 10000:00:02.0: pci_dev_wait: read 0xffffffff DEVSTA 0x0000
>   ...
>   [   10.708367] pci 10000:00:02.0: pci_dev_wait: read 0xffffffff DEVSTA 0x0000
> 
> The 00:02.0 Root Port has RRS SV enabled, but the config reads of the
> 01:00.0 Vendor ID did not return the RRS value (0x0001).  Instead,
> they returned 0xffffffff, which typically means an error on PCIe.