On 21-11-22 16:20:39, Jonathan Cameron wrote:
> On Fri, 19 Nov 2021 16:02:39 -0800
> Ben Widawsky <ben.widawsky@xxxxxxxxx> wrote:
>
> > Endpoints have decoders too. It is useful to share the same
> > infrastructure from cxl_core. Endpoints do not have dports (downstream
> > targets), only the underlying physical medium. As a result, some special
> > casing is needed.
> >
> > There is no functional change introduced yet as endpoints don't actually
> > enumerate decoders yet.
> >
> > Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
>
> I'm not a fan of special values like using 0 here to indicate endpoint
> device. I'd rather see a base cxl_decode_alloc(..., bool ep)
> and possibly wrappers for the non ep case and ep one.
>
> Jonathan
>
My inclination is the opposite. However, I think you and Dan both brought up
something to this effect in the previous RFCs.
Dan, do you have a preference here?
> > ---
> > drivers/cxl/core/bus.c | 41 +++++++++++++++++++++++++++++++++--------
> > 1 file changed, 33 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/cxl/core/bus.c b/drivers/cxl/core/bus.c
> > index 1ee12a60f3f4..16b15f54fb62 100644
> > --- a/drivers/cxl/core/bus.c
> > +++ b/drivers/cxl/core/bus.c
> > @@ -187,6 +187,12 @@ static const struct attribute_group *cxl_decoder_switch_attribute_groups[] = {
> > NULL,
> > };
> >
> > +static const struct attribute_group *cxl_decoder_endpoint_attribute_groups[] = {
> > + &cxl_decoder_base_attribute_group,
> > + &cxl_base_attribute_group,
> > + NULL,
> > +};
> > +
> > static void cxl_decoder_release(struct device *dev)
> > {
> > struct cxl_decoder *cxld = to_cxl_decoder(dev);
> > @@ -196,6 +202,12 @@ static void cxl_decoder_release(struct device *dev)
> > kfree(cxld);
> > }
> >
> > +static const struct device_type cxl_decoder_endpoint_type = {
> > + .name = "cxl_decoder_endpoint",
> > + .release = cxl_decoder_release,
> > + .groups = cxl_decoder_endpoint_attribute_groups,
> > +};
> > +
> > static const struct device_type cxl_decoder_switch_type = {
> > .name = "cxl_decoder_switch",
> > .release = cxl_decoder_release,
> > @@ -208,6 +220,11 @@ static const struct device_type cxl_decoder_root_type = {
> > .groups = cxl_decoder_root_attribute_groups,
> > };
> >
> > +static bool is_endpoint_decoder(struct device *dev)
> > +{
> > + return dev->type == &cxl_decoder_endpoint_type;
> > +}
> > +
> > bool is_root_decoder(struct device *dev)
> > {
> > return dev->type == &cxl_decoder_root_type;
> > @@ -499,7 +516,9 @@ static int decoder_populate_targets(struct cxl_decoder *cxld,
> > * cxl_decoder_alloc - Allocate a new CXL decoder
> > * @port: owning port of this decoder
> > * @nr_targets: downstream targets accessible by this decoder. All upstream
> > - * ports and root ports must have at least 1 target.
> > + * ports and root ports must have at least 1 target. Endpoint
> > + * devices will have 0 targets. Callers wishing to register an
> > + * endpoint device should specify 0.
> > *
> > * A port should contain one or more decoders. Each of those decoders enable
> > * some address space for CXL.mem utilization. A decoder is expected to be
> > @@ -516,7 +535,7 @@ struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port,
> > struct device *dev;
> > int rc = 0;
> >
> > - if (nr_targets > CXL_DECODER_MAX_INTERLEAVE || nr_targets == 0)
> > + if (nr_targets > CXL_DECODER_MAX_INTERLEAVE)
> > return ERR_PTR(-EINVAL);
> >
> > cxld = kzalloc(struct_size(cxld, target, nr_targets), GFP_KERNEL);
> > @@ -535,8 +554,11 @@ struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port,
> > dev->parent = &port->dev;
> > dev->bus = &cxl_bus_type;
> >
> > + /* Endpoints don't have a target list */
> > + if (nr_targets == 0)
> > + dev->type = &cxl_decoder_endpoint_type;
> > /* root ports do not have a cxl_port_type parent */
> > - if (port->dev.parent->type == &cxl_port_type)
> > + else if (port->dev.parent->type == &cxl_port_type)
> > dev->type = &cxl_decoder_switch_type;
> > else
> > dev->type = &cxl_decoder_root_type;
> > @@ -579,12 +601,15 @@ int cxl_decoder_add(struct cxl_decoder *cxld, int *target_map)
> > if (cxld->interleave_ways < 1)
> > return -EINVAL;
> >
> > - port = to_cxl_port(cxld->dev.parent);
> > - rc = decoder_populate_targets(cxld, port, target_map);
> > - if (rc)
> > - return rc;
> > -
> > dev = &cxld->dev;
> > +
> > + port = to_cxl_port(cxld->dev.parent);
> > + if (!is_endpoint_decoder(dev)) {
> > + rc = decoder_populate_targets(cxld, port, target_map);
> > + if (rc)
> > + return rc;
> > + }
> > +
> > rc = dev_set_name(dev, "decoder%d.%d", port->id, cxld->id);
> > if (rc)
> > return rc;
>
