Re: [PATCH v2] of: property: Create devlink between PCI Host bridge and Root Port supplies

[Konrad Dybcio]

On 5/6/26 9:56 AM, Manivannan Sadhasivam wrote:
> Recently, devicetree started to represent the PCI Host bridge supplies like
> PHY in the Root Port nodes as seen in commit 38fcbfbd4207
> ("dt-bindings: PCI: qcom: Move PHY & reset GPIO to Root Port node"). But
> the Host bridge drivers still control the Root Port supplies as a part of
> their controller initialization/deinitialization sequence.
> 
> So the Host bridge drivers end up parsing the Root Port supplies in their
> probe() and control them. A downside to this approach is that the devlink
> dependency between the suppliers and Host bridge is completely broken. Due
> to this, the driver core probes the Host bridge drivers even if the
> supplies are not ready, causing probe deferrals and setup teardowns in
> Host bridge probe().
> 
> These probe deferrals sometime happen over 1000 times (as reported in Qcom
> Glymur platform) leading to a waste of CPU resources and increase in boot
> time. So to fix these unnecessary deferrals, create devlink between the
> Host bridge and Root Port supplies in of_fwnode_add_links(). This will
> allow the driver core to probe the Host bridge drivers only when all Root
> Port supplies are available.
> 
> Reported-by: Bjorn Andersson <andersson@xxxxxxxxxx>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxxxxxxxx>
> ---

Rob, can you pick this one up?

Konrad