Re: [PATCH v7 0/2] PCI: designware-ep: Fix DBI access before core init

Niklas Cassel
2024-01-09T17:59:03Z

On Sun, Jan 07, 2024 at 04:27:07PM +0900, Krzysztof Wilczyński wrote:
> Hello,

Hello Krzysztof, Manivannan,

>
> > This series is the continuation of previous work by Vidya Sagar [1] to fix the
> > issues related to accessing DBI register space before completing the core
> > initialization in some EP platforms like Tegra194/234 and Qcom SM8450.
>
> Applied to controller/dwc-ep, thank you!
>
> [01/02] PCI: designware-ep: Fix DBI access before core init
> https://git.kernel.org/pci/pci/c/d3d13b00a2cf
> [02/02] PCI: designware-ep: Move pci_epc_init_notify() inside dw_pcie_ep_init_complete()
> https://git.kernel.org/pci/pci/c/a171e1d60dad
>
> Krzysztof

Considering that we know that this series introduces new problems
for drivers with a .core_init_notifier (i.e. tegra and qcom), see:
https://lore.kernel.org/linux-pci/ZWYmX8Y%2F7Q9WMxES@x1-carbon/

Do we really want to apply this series as is?

Reading the patch, it appears that (at least some) tegra and
qcom boards currently causes a whole system hang, which IIUC,
renders those boards unusable.

So perhaps the new issues introduced by this series is preferable
to a whole system hang.

As such, I can understand the urgency to merge this series.
However, at the very least, I think that it might be worth amending
the commit message to mention that this will currently not deregister
the dma device in a clean way, leading to e.g. superfluous entries in
/sys/class/dma/ and debugfs warnings being printed to dmesg.

Kind regards,
Niklas