Re: [PATCH 1/3] cxl/mem: Quiet port walking warning

[Dan Williams <dan.j.williams@intel.com>]

Robert Richter wrote:
> On 16.12.22 17:33:32, Dan Williams wrote:
> > The cxl_mem driver attempts to establish, or revalidate, the cxl_port
> > hierarcy to attach a cxl_memdev to a CXL platform topology. There is a
> > natural race (on ACPI platforms) between when the cxl_mem driver
> > attempts to attach and when the cxl_acpi driver establishes the root of
> > the topology.
> > 
> > If cxl_mem_probe() runs first it will iterate to the top of the device
> > topology without finding the CXL platform root. That situation is benign
> > / expected, so stop warning about it. The cxl_acpi driver will poke
> > cxl_mem_probe() to try again once the CXL platform root is established.
> > 
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> > ---
> >  drivers/cxl/core/port.c |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> > index 810e60cc331c..6296d2bc909a 100644
> > --- a/drivers/cxl/core/port.c
> > +++ b/drivers/cxl/core/port.c
> > @@ -1400,8 +1400,8 @@ int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd)
> >  
> >  		uport_dev = dport_dev->parent;
> >  		if (!uport_dev) {
> > -			dev_warn(dev, "at %s no parent for dport: %s\n",
> > -				 dev_name(iter), dev_name(dport_dev));
> > +			dev_dbg(dev, "at %s no parent for dport: %s\n",
> > +				dev_name(iter), dev_name(dport_dev));
> >  			return -ENXIO;
> 
> Maybe we should also change the return code to the common -EAGAIN for
> this case here too? It looks like it is just passed to
> cxl_mem_probe(), so there are probably no side effects of this change.
> The probe is triggered then again by the base driver.

Good point, might as well explicitly return EPROBE_DEFER rather than let
the driver core turn EAGAIN into EPROBE_DEFER. Tests seem to pass with
that change as well.