Re: [RFC PATCH 0/3] PCI: Use Configuration RRS to wait for device ready

Bjorn Helgaas
2024-09-10T00:59:06Z

On Tue, Aug 27, 2024 at 06:48:45PM -0500, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@google.com>
>
> After a device reset, pci_dev_wait() waits for a device to become
> completely ready by polling the PCI_COMMAND register. The spec envisions
> that software would instead poll for the device to stop responding to
> config reads with Completions with Request Retry Status (RRS).
>
> Polling PCI_COMMAND leads to hardware retries that are invisible to
> software and the backoff between software retries doesn't work correctly.
>
> Root Ports are not required to support the Configuration RRS Software
> Visibility feature that prevents hardware retries and makes the RRS
> Completions visible to software, so this series only uses it when available
> and falls back to PCI_COMMAND polling when it's not.
>
> This is completely untested and posted for comments.
>
> Bjorn Helgaas (3):
> PCI: Wait for device readiness with Configuration RRS
> PCI: aardvark: Correct Configuration RRS checking
> PCI: Rename CRS Completion Status to RRS
>
> drivers/bcma/driver_pci_host.c | 10 ++--
> drivers/pci/controller/dwc/pcie-tegra194.c | 18 +++---
> drivers/pci/controller/pci-aardvark.c | 64 +++++++++++-----------
> drivers/pci/controller/pci-xgene.c | 6 +-
> drivers/pci/controller/pcie-iproc.c | 18 +++---
> drivers/pci/pci-bridge-emul.c | 4 +-
> drivers/pci/pci.c | 41 +++++++++-----
> drivers/pci/pci.h | 11 +++-
> drivers/pci/probe.c | 33 +++++------
> include/linux/bcma/bcma_driver_pci.h | 2 +-
> include/linux/pci.h | 1 +
> include/uapi/linux/pci_regs.h | 6 +-
> 12 files changed, 117 insertions(+), 97 deletions(-)

I'd like to merge this unchanged (except for adding credit to
Stanislav in the [1/3] commit log) for v6.12. Let me know if you
test, review, or object.

Bjorn