diff options
| author | Dan Williams | 2022-11-03 17:30:54 -0700 |
|---|---|---|
| committer | Dan Williams | 2022-11-04 16:01:24 -0700 |
| commit | e4f6dfa9ef756a3934a4caf618b1e86e9e8e21d0 (patch) | |
| tree | 9e0823da0fed30893ac89d42f8e6170f7fa9a706 /drivers/cxl/core | |
| parent | e41c8452b9b204689e68756a3836d1d37b617ad5 (diff) | |
cxl/region: Fix 'distance' calculation with passthrough ports
When programming port decode targets, the algorithm wants to ensure that
two devices are compatible to be programmed as peers beneath a given
port. A compatible peer is a target that shares the same dport, and
where that target's interleave position also routes it to the same
dport. Compatibility is determined by the device's interleave position
being >= to distance. For example, if a given dport can only map every
Nth position then positions less than N away from the last target
programmed are incompatible.
The @distance for the host-bridge's cxl_port in a simple dual-ported
host-bridge configuration with 2 direct-attached devices is 1, i.e. An
x2 region divided by 2 dports to reach 2 region targets.
An x4 region under an x2 host-bridge would need 2 intervening switches
where the @distance at the host bridge level is 2 (x4 region divided by
2 switches to reach 4 devices).
However, the distance between peers underneath a single ported
host-bridge is always zero because there is no limit to the number of
devices that can be mapped. In other words, there are no decoders to
program in a passthrough, all descendants are mapped and distance only
starts matters for the intervening descendant ports of the passthrough
port.
Add tracking for the number of dports mapped to a port, and use that to
detect the passthrough case for calculating @distance.
Cc: <stable@vger.kernel.org>
Reported-by: Bobo WL <lmw.bobo@gmail.com>
Reported-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: http://lore.kernel.org/r/20221010172057.00001559@huawei.com
Fixes: 27b3f8d13830 ("cxl/region: Program target lists")
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Link: https://lore.kernel.org/r/166752185440.947915.6617495912508299445.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/cxl/core')
| -rw-r--r-- | drivers/cxl/core/port.c | 11 | ||||
| -rw-r--r-- | drivers/cxl/core/region.c | 9 |
2 files changed, 17 insertions, 3 deletions
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c index bffde862de0b..e7556864ea80 100644 --- a/drivers/cxl/core/port.c +++ b/drivers/cxl/core/port.c @@ -811,6 +811,7 @@ static struct cxl_dport *find_dport(struct cxl_port *port, int id) static int add_dport(struct cxl_port *port, struct cxl_dport *new) { struct cxl_dport *dup; + int rc; device_lock_assert(&port->dev); dup = find_dport(port, new->port_id); @@ -821,8 +822,14 @@ static int add_dport(struct cxl_port *port, struct cxl_dport *new) dev_name(dup->dport)); return -EBUSY; } - return xa_insert(&port->dports, (unsigned long)new->dport, new, - GFP_KERNEL); + + rc = xa_insert(&port->dports, (unsigned long)new->dport, new, + GFP_KERNEL); + if (rc) + return rc; + + port->nr_dports++; + return 0; } /* diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c index c52465e09f26..c0253de74945 100644 --- a/drivers/cxl/core/region.c +++ b/drivers/cxl/core/region.c @@ -990,7 +990,14 @@ static int cxl_port_setup_targets(struct cxl_port *port, if (cxl_rr->nr_targets_set) { int i, distance; - distance = p->nr_targets / cxl_rr->nr_targets; + /* + * Passthrough ports impose no distance requirements between + * peers + */ + if (port->nr_dports == 1) + distance = 0; + else + distance = p->nr_targets / cxl_rr->nr_targets; for (i = 0; i < cxl_rr->nr_targets_set; i++) if (ep->dport == cxlsd->target[i]) { rc = check_last_peer(cxled, ep, cxl_rr, |