On 9/10/2026 11:04 PM, Manivannan Sadhasivam wrote:
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 <[email protected]>
Does this patch help?
https://lore.kernel.org/linux-pci/[email protected]/
- Mani
Thanks for the pointer. I don't think it helps in this case. That patch
enables the Qualcomm ECAM blocker when the Root Port link goes down.
Here, the link between the Root Port and the TC9563 remains up; only
some TC9563 downstream port functions are powered off, and probing those
functions triggers the SError. Therefore, we still need to avoid these
config-space reads.
--
Best regards,
Xilin Wu <[email protected]>
