Re: [PATCH 1/6] PCI: of: Avoid config reads for disabled bridge nodes
From: Manivannan Sadhasivam <mani@kernel.org>
Date: 2026-09-10 15:05:05
Also in:
dri-devel, linux-arm-msm, linux-gpio, linux-pci, lkml
On Tue, Sep 01, 2026 at 04:47:54PM +0800, Xilin Wu wrote:
The TC9563 PCI power-control driver powers off external downstream ports
whose device tree nodes have status = "disabled".
On the Radxa Dragon Q8B, reading the Vendor ID from one of these
powered-off port functions during PCI enumeration raises an Arm SError
instead of returning an all-ones PCI error response. This prevents the
board from completing boot.
Commit 1a8c251cff20 ("PCI: move OF status = "disabled" detection to
dev->match_driver") made disabled PCI functions remain discoverable so
PCI fixups can still be applied, while suppressing driver binding later.
Preserve that behavior for endpoint functions.
For an unavailable node describing a PCI-to-PCI bridge, however, the
node also represents a subordinate bus that must not be enumerated.
Check the device tree node before reading the Vendor ID and return a PCI
error response without accessing config space when such a bridge is
disabled.
Functions not described by device tree and disabled endpoint functions
remain discoverable.
Signed-off-by: Xilin Wu <redacted>Does this patch help? https://lore.kernel.org/linux-pci/20260819-ecam_blocker-v2-1-e7a8fdc1c5cb@oss.qualcomm.com/ (local) - Mani -- மணிவண்ணன் சதாசிவம்