Re: [RFC Patch v1 2/3] cxl/pci: Update Port GPF timeout only when the first EP attaching

[Davidlohr Bueso]

On Wed, 19 Mar 2025, Li Ming wrote:

> If a CXL switch is under a CXL root port, The Port GPF Phase timeout
> will be updated on the CXL root port when each cxl memory device under
> the CXL switch is attaching. It is possible to be updated more than
> once. Actually, it is enough to initialize once, other extra
> initializations are redundant.

It's actually not updated more than necessary because update_gpf_port_dvsec()
checks first:

	if (FIELD_GET(base, ctrl) == GPF_TIMEOUT_BASE_MAX &&
	    FIELD_GET(scale, ctrl) == GPF_TIMEOUT_SCALE_MAX)
		return 0;

> When the first EP attaching, it always triggers its ancestor dports to
> locate their own Port GPF DVSEC. The change is that updating Port GPF
> Phase timeout on these ancestor dports after ancestor dport locating a
> Port GPF DVSEC. It guaranttess that Port GPF Phase timeout updating on a

s/guaranttess/guarantees

> dport only happens during the first EP attaching.

... but yeah, I think this is still better, logically.

Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>

(with the caveat that if patch 1 is not necessary then this would need to
be redone).