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authorDan Williams <dan.j.williams@intel.com>2022-11-04 03:30:54 +0300
committerDan Williams <dan.j.williams@intel.com>2022-11-05 02:01:24 +0300
commite4f6dfa9ef756a3934a4caf618b1e86e9e8e21d0 (patch)
tree9e0823da0fed30893ac89d42f8e6170f7fa9a706 /drivers
parente41c8452b9b204689e68756a3836d1d37b617ad5 (diff)
downloadlinux-e4f6dfa9ef756a3934a4caf618b1e86e9e8e21d0.tar.xz
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')
-rw-r--r--drivers/cxl/core/port.c11
-rw-r--r--drivers/cxl/core/region.c9
-rw-r--r--drivers/cxl/cxl.h2
3 files changed, 19 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,
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 1164ad49f3d3..ac75554b5d76 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -457,6 +457,7 @@ struct cxl_pmem_region {
* @regions: cxl_region_ref instances, regions mapped by this port
* @parent_dport: dport that points to this port in the parent
* @decoder_ida: allocator for decoder ids
+ * @nr_dports: number of entries in @dports
* @hdm_end: track last allocated HDM decoder instance for allocation ordering
* @commit_end: cursor to track highest committed decoder for commit ordering
* @component_reg_phys: component register capability base address (optional)
@@ -475,6 +476,7 @@ struct cxl_port {
struct xarray regions;
struct cxl_dport *parent_dport;
struct ida decoder_ida;
+ int nr_dports;
int hdm_end;
int commit_end;
resource_size_t component_reg_phys;