[PATCH v3 0/7] cxl/region: Refactor cxl_port_setup_targets()

[PATCH v3 0/7] cxl/region: Refactor cxl_port_setup_targets()

[Alison Schofield]

This is a somewhat fast turnaround, and I probably caught Jonathan
midway through looking at v2. My reason (excuse) is that it's a foundation
for another set, so trying to keep it fresh.


Changes in v3:
- Drop patch "cxl/region: Name the interleave locals in cxl_port_setup_targets()".
- Move the distance comment above cxl_port_peer_distance() (Jonathan)
- Name the out-params out_iw/out_ig.
- Minor reverse fir and alignment cleanups
- Reorder the cxl_port_calc_interleave() declarations
v2: https://lore.kernel.org/linux-cxl/cover.1791676454.git.alison.schofield@intel.com/

Changes in v2:
- New patch 3 adds 'switch' to cxl_port_setup_targets() name (DaveJ)
- Add 'switch' to cxl_port_add_target() name (DaveJ)
- Pass the switch decoder to cxl_switch_port_add_target (DaveJ)
- Minor commit message updates based on function renamings
v1: https://lore.kernel.org/linux-cxl/cover.1791575481.git.alison.schofield@intel.com/

Begin Cover Letter:
cxl_port_setup_targets() has grown to nearly 200 lines. It open codes each
step of adding an endpoint to a port's decoder: finding the distance
between peer positions, reading the parent interleave, calculating and
validating the port's interleave, setting up the decoder, and adding the
target.

This set is inspired by review feedback from Robert Richter on the series
that adds mixed-granularity region support [1]. That series needs to change
how this function calculates interleaves and Robert asked for that new code
to be moved into a helper. Rather than tidy only the new code, this set
splits up the whole function first.

Patch 1 prepares the code that moves. It is a suggestion Jonathan offered
on the mixed gran series.

Patch 2 renames the function to cxl_switch_port_setup_targets(), since it
configures switch decoder targets.

Patches 3-7 each move one step at a time into its own helper, which leaves
cxl_switch_port_setup_targets() at 56 lines.

The refactor patches make no functional changes and aim to be mechanical
and easy to review. I tried to avoid all 'while you're at it' changes
that would muddy the mechanical split.

That base commit is from cxl/next.

[1] https://lore.kernel.org/linux-cxl/cover.1788475206.git.alison.schofield@intel.com/

Alison Schofield (7):
  cxl: Add interleave encoding validity helpers
  cxl/region: Rename cxl_port_setup_targets() to
    cxl_switch_port_setup_targets()
  cxl/region: Factor out cxl_port_peer_distance()
  cxl/region: Factor out cxl_port_parent_interleave()
  cxl/region: Factor out cxl_port_calc_interleave()
  cxl/region: Factor out cxl_port_setup_decoder()
  cxl/region: Factor out cxl_switch_port_add_target()

 drivers/cxl/core/region.c | 230 ++++++++++++++++++++++++--------------
 drivers/cxl/cxl.h         |  21 ++++
 2 files changed, 164 insertions(+), 87 deletions(-)


base-commit: 91320b84095afcaf9e4f676eef5b05346d60eb79
-- 
2.37.3

[PATCH v3 1/7] cxl: Add interleave encoding validity helpers

[Alison Schofield]

Some callers of ways_to_eiw(), granularity_to_eig(), and
eig_to_granularity() only need to determine whether an input is valid,
but must provide storage for a converted value that is then discarded.
This obscures the purpose of the call and requires unnecessary temporary
variables.

Define and use new helpers that provide a validation-only interface for
those callers.

cxl_port_setup_targets() also encodes and then decodes its calculated
granularity solely to validate it. Calculate the granularity directly
and validate it instead, making the calculation explicit and removing
the encode/decode round trip.

No functional change.

Suggested-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
---
 drivers/cxl/core/region.c | 49 +++++++++++++--------------------------
 drivers/cxl/cxl.h         | 21 +++++++++++++++++
 2 files changed, 37 insertions(+), 33 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index a048bd5c06cb..bc087ca63946 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -493,11 +493,9 @@ static int set_interleave_ways(struct cxl_region *cxlr, int val)
 	struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
 	struct cxl_region_params *p = &cxlr->params;
 	int save, rc;
-	u8 iw;
 
-	rc = ways_to_eiw(val, &iw);
-	if (rc)
-		return rc;
+	if (!ways_valid(val))
+		return -EINVAL;
 
 	/*
 	 * Even for x3, x6, and x12 interleaves the region interleave must be a
@@ -566,12 +564,9 @@ static int set_interleave_granularity(struct cxl_region *cxlr, int val)
 	struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
 	struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
 	struct cxl_region_params *p = &cxlr->params;
-	int rc;
-	u16 ig;
 
-	rc = granularity_to_eig(val, &ig);
-	if (rc)
-		return rc;
+	if (!granularity_valid(val))
+		return -EINVAL;
 
 	/*
 	 * When the host-bridge is interleaved, disallow region granularity !=
@@ -1451,8 +1446,6 @@ static int cxl_port_setup_targets(struct cxl_port *port,
 	struct cxl_decoder *cxld = cxl_rr->decoder;
 	struct cxl_switch_decoder *cxlsd;
 	struct cxl_port *iter = port;
-	u16 eig, peig;
-	u8 eiw, peiw;
 
 	/*
 	 * While root level decoders support x3, x6, x12, switch level
@@ -1524,48 +1517,38 @@ static int cxl_port_setup_targets(struct cxl_port *port,
 		parent_iw = parent_cxld->interleave_ways;
 	}
 
-	rc = granularity_to_eig(parent_ig, &peig);
-	if (rc) {
+	if (!granularity_valid(parent_ig)) {
 		dev_dbg(&cxlr->dev, "%s:%s: invalid parent granularity: %d\n",
 			dev_name(parent_port->uport_dev),
 			dev_name(&parent_port->dev), parent_ig);
-		return rc;
+		return -EINVAL;
 	}
 
-	rc = ways_to_eiw(parent_iw, &peiw);
-	if (rc) {
+	if (!ways_valid(parent_iw)) {
 		dev_dbg(&cxlr->dev, "%s:%s: invalid parent interleave: %d\n",
 			dev_name(parent_port->uport_dev),
 			dev_name(&parent_port->dev), parent_iw);
-		return rc;
+		return -EINVAL;
 	}
 
 	iw = cxl_rr->nr_targets;
-	rc = ways_to_eiw(iw, &eiw);
-	if (rc) {
+	if (!ways_valid(iw)) {
 		dev_dbg(&cxlr->dev, "%s:%s: invalid port interleave: %d\n",
 			dev_name(port->uport_dev), dev_name(&port->dev), iw);
-		return rc;
+		return -EINVAL;
 	}
 
 	/*
 	 * Interleave granularity is a multiple of @parent_port granularity.
 	 * Multiplier is the parent port interleave ways.
 	 */
-	rc = granularity_to_eig(parent_ig * parent_iw, &eig);
-	if (rc) {
+	ig = parent_ig * parent_iw;
+
+	if (!granularity_valid(ig)) {
 		dev_dbg(&cxlr->dev,
 			"%s: invalid granularity calculation (%d * %d)\n",
 			dev_name(&parent_port->dev), parent_ig, parent_iw);
-		return rc;
-	}
-
-	rc = eig_to_granularity(eig, &ig);
-	if (rc) {
-		dev_dbg(&cxlr->dev, "%s:%s: invalid interleave: %d\n",
-			dev_name(port->uport_dev), dev_name(&port->dev),
-			256 << eig);
-		return rc;
+		return -EINVAL;
 	}
 
 	if (iw > 8 || iw > cxlsd->nr_targets) {
@@ -3131,13 +3114,13 @@ static bool cxl_is_hpa_in_chunk(u64 hpa, struct cxl_region *cxlr, int pos)
  */
 int cxl_validate_translation_params(u8 eiw, u16 eig, int pos)
 {
-	int ways, gran;
+	int ways;
 
 	if (eiw_to_ways(eiw, &ways)) {
 		pr_debug("%s: invalid eiw=%u\n", __func__, eiw);
 		return -EINVAL;
 	}
-	if (eig_to_granularity(eig, &gran)) {
+	if (!eig_valid(eig)) {
 		pr_debug("%s: invalid eig=%u\n", __func__, eig);
 		return -EINVAL;
 	}
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index d96210b8f147..8f0a79e7b8ab 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -146,6 +146,27 @@ static inline int ways_to_eiw(unsigned int ways, u8 *eiw)
 	return 0;
 }
 
+static inline bool eig_valid(u16 eig)
+{
+	int granularity;
+
+	return eig_to_granularity(eig, &granularity) == 0;
+}
+
+static inline bool granularity_valid(int granularity)
+{
+	u16 eig;
+
+	return granularity_to_eig(granularity, &eig) == 0;
+}
+
+static inline bool ways_valid(unsigned int ways)
+{
+	u8 eiw;
+
+	return ways_to_eiw(ways, &eiw) == 0;
+}
+
 /* RAS Registers CXL 2.0 8.2.5.9 CXL RAS Capability Structure */
 #define CXL_RAS_UNCORRECTABLE_STATUS_OFFSET 0x0
 #define   CXL_RAS_UNCORRECTABLE_STATUS_MASK (GENMASK(16, 14) | GENMASK(11, 0))
-- 
2.37.3

[PATCH v3 2/7] cxl/region: Rename cxl_port_setup_targets() to cxl_switch_port_setup_targets()

[Alison Schofield]

cxl_port_setup_targets() configures the switch decoder targets for a
region. It runs for each switch port, including host bridges, between the
root and an endpoint.

Rename the function to cxl_switch_port_setup_targets() to make its scope
explicit.

No functional change.

Suggested-by: Dave Jiang <dave.jiang@intel.com>
Assisted-by: LLM
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
---
 drivers/cxl/core/region.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index bc087ca63946..9b0e2f195d1f 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1432,9 +1432,9 @@ static int check_interleave_cap(struct cxl_decoder *cxld, int iw, int ig)
 	return 0;
 }
 
-static int cxl_port_setup_targets(struct cxl_port *port,
-				  struct cxl_region *cxlr,
-				  struct cxl_endpoint_decoder *cxled)
+static int cxl_switch_port_setup_targets(struct cxl_port *port,
+					 struct cxl_region *cxlr,
+					 struct cxl_endpoint_decoder *cxled)
 {
 	struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
 	int parent_iw, parent_ig, ig, iw, rc, pos = cxled->pos;
@@ -1716,7 +1716,7 @@ static int cxl_region_setup_targets(struct cxl_region *cxlr)
 		 */
 		for (ep = cxl_ep_load(iter, cxlmd); iter;
 		     iter = ep->next, ep = cxl_ep_load(iter, cxlmd)) {
-			rc = cxl_port_setup_targets(iter, cxlr, cxled);
+			rc = cxl_switch_port_setup_targets(iter, cxlr, cxled);
 			if (rc) {
 				cxl_region_teardown_targets(cxlr);
 				return rc;
-- 
2.37.3

[PATCH v3 3/7] cxl/region: Factor out cxl_port_peer_distance()

[Alison Schofield]

cxl_switch_port_setup_targets() is nearly 200 lines long and open codes
each step of adding an endpoint to a port's decoder. One of those steps
calculates the distance between region positions that share a downstream
port.

Move that calculation to a new helper, cxl_port_peer_distance().

No functional change.

Assisted-by: LLM
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
---
 drivers/cxl/core/region.c | 50 +++++++++++++++++++++++----------------
 1 file changed, 29 insertions(+), 21 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 9b0e2f195d1f..ea281ce4ec49 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1432,6 +1432,33 @@ static int check_interleave_cap(struct cxl_decoder *cxld, int iw, int ig)
 	return 0;
 }
 
+/*
+ * The "distance" between peer downstream ports represents which
+ * endpoint positions in the region interleave a given port can
+ * host.
+ *
+ * For example, at the root of a hierarchy the distance is
+ * always 1 as every index targets a different host-bridge. At
+ * each subsequent switch level those ports map every Nth region
+ * position where N is the width of the switch == distance.
+ */
+static int cxl_port_peer_distance(struct cxl_port *port, struct cxl_region *cxlr)
+{
+	struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
+	struct cxl_region_ref *cxl_rr_iter;
+	struct cxl_port *iter = port;
+	int distance = 1;
+
+	do {
+		cxl_rr_iter = cxl_rr_load(iter, cxlr);
+		distance *= cxl_rr_iter->nr_targets;
+		iter = to_cxl_port(iter->dev.parent);
+	} while (!is_cxl_root(iter));
+	distance *= cxlrd->cxlsd.cxld.interleave_ways;
+
+	return distance;
+}
+
 static int cxl_switch_port_setup_targets(struct cxl_port *port,
 					 struct cxl_region *cxlr,
 					 struct cxl_endpoint_decoder *cxled)
@@ -1445,7 +1472,6 @@ static int cxl_switch_port_setup_targets(struct cxl_port *port,
 	struct cxl_region_params *p = &cxlr->params;
 	struct cxl_decoder *cxld = cxl_rr->decoder;
 	struct cxl_switch_decoder *cxlsd;
-	struct cxl_port *iter = port;
 
 	/*
 	 * While root level decoders support x3, x6, x12, switch level
@@ -1460,27 +1486,9 @@ static int cxl_switch_port_setup_targets(struct cxl_port *port,
 
 	cxlsd = to_cxl_switch_decoder(&cxld->dev);
 	if (cxl_rr->nr_targets_set) {
-		int i, distance = 1;
-		struct cxl_region_ref *cxl_rr_iter;
+		int distance = cxl_port_peer_distance(port, cxlr);
 
-		/*
-		 * The "distance" between peer downstream ports represents which
-		 * endpoint positions in the region interleave a given port can
-		 * host.
-		 *
-		 * For example, at the root of a hierarchy the distance is
-		 * always 1 as every index targets a different host-bridge. At
-		 * each subsequent switch level those ports map every Nth region
-		 * position where N is the width of the switch == distance.
-		 */
-		do {
-			cxl_rr_iter = cxl_rr_load(iter, cxlr);
-			distance *= cxl_rr_iter->nr_targets;
-			iter = to_cxl_port(iter->dev.parent);
-		} while (!is_cxl_root(iter));
-		distance *= cxlrd->cxlsd.cxld.interleave_ways;
-
-		for (i = 0; i < cxl_rr->nr_targets_set; i++)
+		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
 			if (ep->dport == cxlsd->target[i]) {
 				rc = check_last_peer(cxled, ep, cxl_rr,
 						     distance);
-- 
2.37.3

[PATCH v3 4/7] cxl/region: Factor out cxl_port_parent_interleave()

[Alison Schofield]

cxl_switch_port_setup_targets() derives a decoder's interleave from the
interleave of the decoder above it. That parent interleave comes from
either the root decoder or a switch decoder, and each case is open coded
along with the parent validity checks.

Move the parent interleave lookup and validation to a new helper,
cxl_port_parent_interleave().

No functional change.

Assisted-by: LLM
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---
 drivers/cxl/core/region.c | 88 +++++++++++++++++++++++----------------
 1 file changed, 52 insertions(+), 36 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index ea281ce4ec49..c14ac041c4ac 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1459,45 +1459,13 @@ static int cxl_port_peer_distance(struct cxl_port *port, struct cxl_region *cxlr
 	return distance;
 }
 
-static int cxl_switch_port_setup_targets(struct cxl_port *port,
-					 struct cxl_region *cxlr,
-					 struct cxl_endpoint_decoder *cxled)
+static int cxl_port_parent_interleave(struct cxl_port *port, struct cxl_region *cxlr,
+				      int *out_iw, int *out_ig)
 {
-	struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
-	int parent_iw, parent_ig, ig, iw, rc, pos = cxled->pos;
 	struct cxl_port *parent_port = to_cxl_port(port->dev.parent);
-	struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
-	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
-	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
+	struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
 	struct cxl_region_params *p = &cxlr->params;
-	struct cxl_decoder *cxld = cxl_rr->decoder;
-	struct cxl_switch_decoder *cxlsd;
-
-	/*
-	 * While root level decoders support x3, x6, x12, switch level
-	 * decoders only support powers of 2 up to x16.
-	 */
-	if (!is_power_of_2(cxl_rr->nr_targets)) {
-		dev_dbg(&cxlr->dev, "%s:%s: invalid target count %d\n",
-			dev_name(port->uport_dev), dev_name(&port->dev),
-			cxl_rr->nr_targets);
-		return -EINVAL;
-	}
-
-	cxlsd = to_cxl_switch_decoder(&cxld->dev);
-	if (cxl_rr->nr_targets_set) {
-		int distance = cxl_port_peer_distance(port, cxlr);
-
-		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
-			if (ep->dport == cxlsd->target[i]) {
-				rc = check_last_peer(cxled, ep, cxl_rr,
-						     distance);
-				if (rc)
-					return rc;
-				goto out_target_set;
-			}
-		goto add_target;
-	}
+	int parent_iw, parent_ig;
 
 	if (is_cxl_root(parent_port)) {
 		/*
@@ -1539,6 +1507,54 @@ static int cxl_switch_port_setup_targets(struct cxl_port *port,
 		return -EINVAL;
 	}
 
+	*out_iw = parent_iw;
+	*out_ig = parent_ig;
+
+	return 0;
+}
+
+static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_region *cxlr,
+					 struct cxl_endpoint_decoder *cxled)
+{
+	int parent_iw, parent_ig, ig, iw, rc, pos = cxled->pos;
+	struct cxl_port *parent_port = to_cxl_port(port->dev.parent);
+	struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
+	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
+	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
+	struct cxl_region_params *p = &cxlr->params;
+	struct cxl_decoder *cxld = cxl_rr->decoder;
+	struct cxl_switch_decoder *cxlsd;
+
+	/*
+	 * While root level decoders support x3, x6, x12, switch level
+	 * decoders only support powers of 2 up to x16.
+	 */
+	if (!is_power_of_2(cxl_rr->nr_targets)) {
+		dev_dbg(&cxlr->dev, "%s:%s: invalid target count %d\n",
+			dev_name(port->uport_dev), dev_name(&port->dev),
+			cxl_rr->nr_targets);
+		return -EINVAL;
+	}
+
+	cxlsd = to_cxl_switch_decoder(&cxld->dev);
+	if (cxl_rr->nr_targets_set) {
+		int distance = cxl_port_peer_distance(port, cxlr);
+
+		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
+			if (ep->dport == cxlsd->target[i]) {
+				rc = check_last_peer(cxled, ep, cxl_rr,
+						     distance);
+				if (rc)
+					return rc;
+				goto out_target_set;
+			}
+		goto add_target;
+	}
+
+	rc = cxl_port_parent_interleave(port, cxlr, &parent_iw, &parent_ig);
+	if (rc)
+		return rc;
+
 	iw = cxl_rr->nr_targets;
 	if (!ways_valid(iw)) {
 		dev_dbg(&cxlr->dev, "%s:%s: invalid port interleave: %d\n",
-- 
2.37.3

[PATCH v3 5/7] cxl/region: Factor out cxl_port_calc_interleave()

[Alison Schofield]

cxl_switch_port_setup_targets() calculates the interleave ways and
granularity of a port's decoder from the parent interleave and the number
of targets below the port, then validates the result. That calculation and
its checks are open coded between the target search and the decoder setup.

Move the calculation and its checks to a new helper,
cxl_port_calc_interleave(), so that the interleave for the port's decoder
is calculated and validated in one place.

No functional change.

Assisted-by: LLM
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
---
 drivers/cxl/core/region.c | 81 ++++++++++++++++++++++++---------------
 1 file changed, 50 insertions(+), 31 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index c14ac041c4ac..ee9e615a9a4c 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1513,11 +1513,58 @@ static int cxl_port_parent_interleave(struct cxl_port *port, struct cxl_region *
 	return 0;
 }
 
+static int cxl_port_calc_interleave(struct cxl_port *port, struct cxl_region *cxlr,
+				    struct cxl_region_ref *cxl_rr, int *out_iw,
+				    int *out_ig)
+{
+	struct cxl_port *parent_port = to_cxl_port(port->dev.parent);
+	struct cxl_decoder *cxld = cxl_rr->decoder;
+	int parent_iw, parent_ig, iw, ig, rc;
+	struct cxl_switch_decoder *cxlsd;
+
+	rc = cxl_port_parent_interleave(port, cxlr, &parent_iw, &parent_ig);
+	if (rc)
+		return rc;
+
+	iw = cxl_rr->nr_targets;
+	if (!ways_valid(iw)) {
+		dev_dbg(&cxlr->dev, "%s:%s: invalid port interleave: %d\n",
+			dev_name(port->uport_dev), dev_name(&port->dev), iw);
+		return -EINVAL;
+	}
+
+	/*
+	 * Interleave granularity is a multiple of @parent_port granularity.
+	 * Multiplier is the parent port interleave ways.
+	 */
+	ig = parent_ig * parent_iw;
+
+	if (!granularity_valid(ig)) {
+		dev_dbg(&cxlr->dev,
+			"%s: invalid granularity calculation (%d * %d)\n",
+			dev_name(&parent_port->dev), parent_ig, parent_iw);
+		return -EINVAL;
+	}
+
+	cxlsd = to_cxl_switch_decoder(&cxld->dev);
+	if (iw > 8 || iw > cxlsd->nr_targets) {
+		dev_dbg(&cxlr->dev,
+			"%s:%s:%s: ways: %d overflows targets: %d\n",
+			dev_name(port->uport_dev), dev_name(&port->dev),
+			dev_name(&cxld->dev), iw, cxlsd->nr_targets);
+		return -ENXIO;
+	}
+
+	*out_iw = iw;
+	*out_ig = ig;
+
+	return 0;
+}
+
 static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_region *cxlr,
 					 struct cxl_endpoint_decoder *cxled)
 {
-	int parent_iw, parent_ig, ig, iw, rc, pos = cxled->pos;
-	struct cxl_port *parent_port = to_cxl_port(port->dev.parent);
+	int iw, ig, rc, pos = cxled->pos;
 	struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
 	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
 	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
@@ -1551,38 +1598,10 @@ static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_regio
 		goto add_target;
 	}
 
-	rc = cxl_port_parent_interleave(port, cxlr, &parent_iw, &parent_ig);
+	rc = cxl_port_calc_interleave(port, cxlr, cxl_rr, &iw, &ig);
 	if (rc)
 		return rc;
 
-	iw = cxl_rr->nr_targets;
-	if (!ways_valid(iw)) {
-		dev_dbg(&cxlr->dev, "%s:%s: invalid port interleave: %d\n",
-			dev_name(port->uport_dev), dev_name(&port->dev), iw);
-		return -EINVAL;
-	}
-
-	/*
-	 * Interleave granularity is a multiple of @parent_port granularity.
-	 * Multiplier is the parent port interleave ways.
-	 */
-	ig = parent_ig * parent_iw;
-
-	if (!granularity_valid(ig)) {
-		dev_dbg(&cxlr->dev,
-			"%s: invalid granularity calculation (%d * %d)\n",
-			dev_name(&parent_port->dev), parent_ig, parent_iw);
-		return -EINVAL;
-	}
-
-	if (iw > 8 || iw > cxlsd->nr_targets) {
-		dev_dbg(&cxlr->dev,
-			"%s:%s:%s: ways: %d overflows targets: %d\n",
-			dev_name(port->uport_dev), dev_name(&port->dev),
-			dev_name(&cxld->dev), iw, cxlsd->nr_targets);
-		return -ENXIO;
-	}
-
 	if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags)) {
 		if (cxld->interleave_ways != iw ||
 		    (iw > 1 && cxld->interleave_granularity != ig) ||
-- 
2.37.3

[PATCH v3 6/7] cxl/region: Factor out cxl_port_setup_decoder()

[Alison Schofield]

Once cxl_switch_port_setup_targets() has calculated the interleave for a
port's decoder, it either checks that interleave against the decoder
settings found for an auto region, or checks the decoder's interleave
capabilities and programs the decoder for a user created region. Both paths
are open coded in cxl_switch_port_setup_targets().

Move both paths to a new helper, cxl_port_setup_decoder().

No functional change.

Assisted-by: LLM
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
---
 drivers/cxl/core/region.c | 88 ++++++++++++++++++++++-----------------
 1 file changed, 50 insertions(+), 38 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index ee9e615a9a4c..229372123271 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1561,46 +1561,11 @@ static int cxl_port_calc_interleave(struct cxl_port *port, struct cxl_region *cx
 	return 0;
 }
 
-static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_region *cxlr,
-					 struct cxl_endpoint_decoder *cxled)
+static int cxl_port_setup_decoder(struct cxl_port *port, struct cxl_region *cxlr,
+				  struct cxl_decoder *cxld, int iw, int ig)
 {
-	int iw, ig, rc, pos = cxled->pos;
-	struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
-	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
-	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
 	struct cxl_region_params *p = &cxlr->params;
-	struct cxl_decoder *cxld = cxl_rr->decoder;
-	struct cxl_switch_decoder *cxlsd;
-
-	/*
-	 * While root level decoders support x3, x6, x12, switch level
-	 * decoders only support powers of 2 up to x16.
-	 */
-	if (!is_power_of_2(cxl_rr->nr_targets)) {
-		dev_dbg(&cxlr->dev, "%s:%s: invalid target count %d\n",
-			dev_name(port->uport_dev), dev_name(&port->dev),
-			cxl_rr->nr_targets);
-		return -EINVAL;
-	}
-
-	cxlsd = to_cxl_switch_decoder(&cxld->dev);
-	if (cxl_rr->nr_targets_set) {
-		int distance = cxl_port_peer_distance(port, cxlr);
-
-		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
-			if (ep->dport == cxlsd->target[i]) {
-				rc = check_last_peer(cxled, ep, cxl_rr,
-						     distance);
-				if (rc)
-					return rc;
-				goto out_target_set;
-			}
-		goto add_target;
-	}
-
-	rc = cxl_port_calc_interleave(port, cxlr, cxl_rr, &iw, &ig);
-	if (rc)
-		return rc;
+	int rc;
 
 	if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags)) {
 		if (cxld->interleave_ways != iw ||
@@ -1639,6 +1604,53 @@ static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_regio
 	}
 	dev_dbg(&cxlr->dev, "%s:%s iw: %d ig: %d\n", dev_name(port->uport_dev),
 		dev_name(&port->dev), iw, ig);
+
+	return 0;
+}
+
+static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_region *cxlr,
+					 struct cxl_endpoint_decoder *cxled)
+{
+	int iw, ig, rc, pos = cxled->pos;
+	struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
+	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
+	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
+	struct cxl_decoder *cxld = cxl_rr->decoder;
+	struct cxl_switch_decoder *cxlsd;
+
+	/*
+	 * While root level decoders support x3, x6, x12, switch level
+	 * decoders only support powers of 2 up to x16.
+	 */
+	if (!is_power_of_2(cxl_rr->nr_targets)) {
+		dev_dbg(&cxlr->dev, "%s:%s: invalid target count %d\n",
+			dev_name(port->uport_dev), dev_name(&port->dev),
+			cxl_rr->nr_targets);
+		return -EINVAL;
+	}
+
+	cxlsd = to_cxl_switch_decoder(&cxld->dev);
+	if (cxl_rr->nr_targets_set) {
+		int distance = cxl_port_peer_distance(port, cxlr);
+
+		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
+			if (ep->dport == cxlsd->target[i]) {
+				rc = check_last_peer(cxled, ep, cxl_rr,
+						     distance);
+				if (rc)
+					return rc;
+				goto out_target_set;
+			}
+		goto add_target;
+	}
+
+	rc = cxl_port_calc_interleave(port, cxlr, cxl_rr, &iw, &ig);
+	if (rc)
+		return rc;
+
+	rc = cxl_port_setup_decoder(port, cxlr, cxld, iw, ig);
+	if (rc)
+		return rc;
 add_target:
 	if (cxl_rr->nr_targets_set == cxl_rr->nr_targets) {
 		dev_dbg(&cxlr->dev,
-- 
2.37.3

[PATCH v3 7/7] cxl/region: Factor out cxl_switch_port_add_target()

[Alison Schofield]

cxl_switch_port_setup_targets() adds an endpoint's downstream port to a
port's decoder target list. For an auto region it checks that the decoder
already targets that downstream port at the next position. For a user
created region it programs the downstream port at that position. That step
is open coded behind an add_target label that the target search jumps to.

Move that step to a new helper, cxl_switch_port_add_target(). The helper
takes the switch decoder whose target list it updates, rather than the
port, which makes its scope explicit. With the decoder setup and the
target add now in helpers, the path for the first endpoint to reach a port
becomes an else branch of the target search, so the add_target label is
no longer needed.

No functional change.

Assisted-by: LLM
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---
 drivers/cxl/core/region.c | 80 ++++++++++++++++++++++++---------------
 1 file changed, 49 insertions(+), 31 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 229372123271..50f4830c225d 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1608,15 +1608,50 @@ static int cxl_port_setup_decoder(struct cxl_port *port, struct cxl_region *cxlr
 	return 0;
 }
 
+static int cxl_switch_port_add_target(struct cxl_switch_decoder *cxlsd,
+				      struct cxl_region *cxlr,
+				      struct cxl_region_ref *cxl_rr,
+				      struct cxl_endpoint_decoder *cxled,
+				      struct cxl_ep *ep)
+{
+	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
+	struct cxl_port *port = cxl_rr->port;
+	int pos = cxled->pos;
+
+	if (cxl_rr->nr_targets_set == cxl_rr->nr_targets) {
+		dev_dbg(&cxlr->dev,
+			"%s:%s: targets full trying to add %s:%s at %d\n",
+			dev_name(port->uport_dev), dev_name(&port->dev),
+			dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev), pos);
+		return -ENXIO;
+	}
+	if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags)) {
+		if (cxlsd->target[cxl_rr->nr_targets_set] != ep->dport) {
+			dev_dbg(&cxlr->dev, "%s:%s: %s expected %s at %d\n",
+				dev_name(port->uport_dev), dev_name(&port->dev),
+				dev_name(&cxlsd->cxld.dev),
+				dev_name(ep->dport->dport_dev),
+				cxl_rr->nr_targets_set);
+			return -ENXIO;
+		}
+	} else {
+		cxlsd->target[cxl_rr->nr_targets_set] = ep->dport;
+		cxlsd->cxld.target_map[cxl_rr->nr_targets_set] = ep->dport->port_id;
+	}
+	cxl_rr->nr_targets_set++;
+
+	return 0;
+}
+
 static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_region *cxlr,
 					 struct cxl_endpoint_decoder *cxled)
 {
-	int iw, ig, rc, pos = cxled->pos;
 	struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
 	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
 	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
 	struct cxl_decoder *cxld = cxl_rr->decoder;
 	struct cxl_switch_decoder *cxlsd;
+	int rc, pos = cxled->pos;
 
 	/*
 	 * While root level decoders support x3, x6, x12, switch level
@@ -1641,38 +1676,21 @@ static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_regio
 					return rc;
 				goto out_target_set;
 			}
-		goto add_target;
-	}
-
-	rc = cxl_port_calc_interleave(port, cxlr, cxl_rr, &iw, &ig);
-	if (rc)
-		return rc;
-
-	rc = cxl_port_setup_decoder(port, cxlr, cxld, iw, ig);
-	if (rc)
-		return rc;
-add_target:
-	if (cxl_rr->nr_targets_set == cxl_rr->nr_targets) {
-		dev_dbg(&cxlr->dev,
-			"%s:%s: targets full trying to add %s:%s at %d\n",
-			dev_name(port->uport_dev), dev_name(&port->dev),
-			dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev), pos);
-		return -ENXIO;
-	}
-	if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags)) {
-		if (cxlsd->target[cxl_rr->nr_targets_set] != ep->dport) {
-			dev_dbg(&cxlr->dev, "%s:%s: %s expected %s at %d\n",
-				dev_name(port->uport_dev), dev_name(&port->dev),
-				dev_name(&cxlsd->cxld.dev),
-				dev_name(ep->dport->dport_dev),
-				cxl_rr->nr_targets_set);
-			return -ENXIO;
-		}
 	} else {
-		cxlsd->target[cxl_rr->nr_targets_set] = ep->dport;
-		cxlsd->cxld.target_map[cxl_rr->nr_targets_set] = ep->dport->port_id;
+		int iw, ig;
+
+		rc = cxl_port_calc_interleave(port, cxlr, cxl_rr, &iw, &ig);
+		if (rc)
+			return rc;
+
+		rc = cxl_port_setup_decoder(port, cxlr, cxld, iw, ig);
+		if (rc)
+			return rc;
 	}
-	cxl_rr->nr_targets_set++;
+
+	rc = cxl_switch_port_add_target(cxlsd, cxlr, cxl_rr, cxled, ep);
+	if (rc)
+		return rc;
 out_target_set:
 	dev_dbg(&cxlr->dev, "%s:%s target[%d] = %s for %s:%s @ %d\n",
 		dev_name(port->uport_dev), dev_name(&port->dev),
-- 
2.37.3

Re: [PATCH v3 1/7] cxl: Add interleave encoding validity helpers

[Li Ming]

在 2026/10/13 12:25, Alison Schofield 写道:
> Some callers of ways_to_eiw(), granularity_to_eig(), and
> eig_to_granularity() only need to determine whether an input is valid,
> but must provide storage for a converted value that is then discarded.
> This obscures the purpose of the call and requires unnecessary temporary
> variables.
>
> Define and use new helpers that provide a validation-only interface for
> those callers.
>
> cxl_port_setup_targets() also encodes and then decodes its calculated
> granularity solely to validate it. Calculate the granularity directly
> and validate it instead, making the calculation explicit and removing
> the encode/decode round trip.
>
> No functional change.
>
> Suggested-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>

> ---
>   drivers/cxl/core/region.c | 49 +++++++++++++--------------------------
>   drivers/cxl/cxl.h         | 21 +++++++++++++++++
>   2 files changed, 37 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index a048bd5c06cb..bc087ca63946 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -493,11 +493,9 @@ static int set_interleave_ways(struct cxl_region *cxlr, int val)
>   	struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
>   	struct cxl_region_params *p = &cxlr->params;
>   	int save, rc;
> -	u8 iw;
>   
> -	rc = ways_to_eiw(val, &iw);
> -	if (rc)
> -		return rc;
> +	if (!ways_valid(val))
> +		return -EINVAL;
>   
>   	/*
>   	 * Even for x3, x6, and x12 interleaves the region interleave must be a
> @@ -566,12 +564,9 @@ static int set_interleave_granularity(struct cxl_region *cxlr, int val)
>   	struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
>   	struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
>   	struct cxl_region_params *p = &cxlr->params;
> -	int rc;
> -	u16 ig;
>   
> -	rc = granularity_to_eig(val, &ig);
> -	if (rc)
> -		return rc;
> +	if (!granularity_valid(val))
> +		return -EINVAL;
>   
>   	/*
>   	 * When the host-bridge is interleaved, disallow region granularity !=
> @@ -1451,8 +1446,6 @@ static int cxl_port_setup_targets(struct cxl_port *port,
>   	struct cxl_decoder *cxld = cxl_rr->decoder;
>   	struct cxl_switch_decoder *cxlsd;
>   	struct cxl_port *iter = port;
> -	u16 eig, peig;
> -	u8 eiw, peiw;
>   
>   	/*
>   	 * While root level decoders support x3, x6, x12, switch level
> @@ -1524,48 +1517,38 @@ static int cxl_port_setup_targets(struct cxl_port *port,
>   		parent_iw = parent_cxld->interleave_ways;
>   	}
>   
> -	rc = granularity_to_eig(parent_ig, &peig);
> -	if (rc) {
> +	if (!granularity_valid(parent_ig)) {
>   		dev_dbg(&cxlr->dev, "%s:%s: invalid parent granularity: %d\n",
>   			dev_name(parent_port->uport_dev),
>   			dev_name(&parent_port->dev), parent_ig);
> -		return rc;
> +		return -EINVAL;
>   	}
>   
> -	rc = ways_to_eiw(parent_iw, &peiw);
> -	if (rc) {
> +	if (!ways_valid(parent_iw)) {
>   		dev_dbg(&cxlr->dev, "%s:%s: invalid parent interleave: %d\n",
>   			dev_name(parent_port->uport_dev),
>   			dev_name(&parent_port->dev), parent_iw);
> -		return rc;
> +		return -EINVAL;
>   	}
>   
>   	iw = cxl_rr->nr_targets;
> -	rc = ways_to_eiw(iw, &eiw);
> -	if (rc) {
> +	if (!ways_valid(iw)) {
>   		dev_dbg(&cxlr->dev, "%s:%s: invalid port interleave: %d\n",
>   			dev_name(port->uport_dev), dev_name(&port->dev), iw);
> -		return rc;
> +		return -EINVAL;
>   	}
>   
>   	/*
>   	 * Interleave granularity is a multiple of @parent_port granularity.
>   	 * Multiplier is the parent port interleave ways.
>   	 */
> -	rc = granularity_to_eig(parent_ig * parent_iw, &eig);
> -	if (rc) {
> +	ig = parent_ig * parent_iw;
> +
> +	if (!granularity_valid(ig)) {
>   		dev_dbg(&cxlr->dev,
>   			"%s: invalid granularity calculation (%d * %d)\n",
>   			dev_name(&parent_port->dev), parent_ig, parent_iw);
> -		return rc;
> -	}
> -
> -	rc = eig_to_granularity(eig, &ig);
> -	if (rc) {
> -		dev_dbg(&cxlr->dev, "%s:%s: invalid interleave: %d\n",
> -			dev_name(port->uport_dev), dev_name(&port->dev),
> -			256 << eig);
> -		return rc;
> +		return -EINVAL;
>   	}
>   
>   	if (iw > 8 || iw > cxlsd->nr_targets) {
> @@ -3131,13 +3114,13 @@ static bool cxl_is_hpa_in_chunk(u64 hpa, struct cxl_region *cxlr, int pos)
>    */
>   int cxl_validate_translation_params(u8 eiw, u16 eig, int pos)
>   {
> -	int ways, gran;
> +	int ways;
>   
>   	if (eiw_to_ways(eiw, &ways)) {
>   		pr_debug("%s: invalid eiw=%u\n", __func__, eiw);
>   		return -EINVAL;
>   	}
> -	if (eig_to_granularity(eig, &gran)) {
> +	if (!eig_valid(eig)) {
>   		pr_debug("%s: invalid eig=%u\n", __func__, eig);
>   		return -EINVAL;
>   	}
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index d96210b8f147..8f0a79e7b8ab 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -146,6 +146,27 @@ static inline int ways_to_eiw(unsigned int ways, u8 *eiw)
>   	return 0;
>   }
>   
> +static inline bool eig_valid(u16 eig)
> +{
> +	int granularity;
> +
> +	return eig_to_granularity(eig, &granularity) == 0;
> +}
> +
> +static inline bool granularity_valid(int granularity)
> +{
> +	u16 eig;
> +
> +	return granularity_to_eig(granularity, &eig) == 0;
> +}
> +
> +static inline bool ways_valid(unsigned int ways)
> +{
> +	u8 eiw;
> +
> +	return ways_to_eiw(ways, &eiw) == 0;
> +}
> +
>   /* RAS Registers CXL 2.0 8.2.5.9 CXL RAS Capability Structure */
>   #define CXL_RAS_UNCORRECTABLE_STATUS_OFFSET 0x0
>   #define   CXL_RAS_UNCORRECTABLE_STATUS_MASK (GENMASK(16, 14) | GENMASK(11, 0))

Re: [PATCH v3 2/7] cxl/region: Rename cxl_port_setup_targets() to cxl_switch_port_setup_targets()

[Li Ming]

在 2026/10/13 12:25, Alison Schofield 写道:
> cxl_port_setup_targets() configures the switch decoder targets for a
> region. It runs for each switch port, including host bridges, between the
> root and an endpoint.
>
> Rename the function to cxl_switch_port_setup_targets() to make its scope
> explicit.
>
> No functional change.
>
> Suggested-by: Dave Jiang <dave.jiang@intel.com>
> Assisted-by: LLM
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>

> ---
>   drivers/cxl/core/region.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index bc087ca63946..9b0e2f195d1f 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1432,9 +1432,9 @@ static int check_interleave_cap(struct cxl_decoder *cxld, int iw, int ig)
>   	return 0;
>   }
>   
> -static int cxl_port_setup_targets(struct cxl_port *port,
> -				  struct cxl_region *cxlr,
> -				  struct cxl_endpoint_decoder *cxled)
> +static int cxl_switch_port_setup_targets(struct cxl_port *port,
> +					 struct cxl_region *cxlr,
> +					 struct cxl_endpoint_decoder *cxled)
>   {
>   	struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
>   	int parent_iw, parent_ig, ig, iw, rc, pos = cxled->pos;
> @@ -1716,7 +1716,7 @@ static int cxl_region_setup_targets(struct cxl_region *cxlr)
>   		 */
>   		for (ep = cxl_ep_load(iter, cxlmd); iter;
>   		     iter = ep->next, ep = cxl_ep_load(iter, cxlmd)) {
> -			rc = cxl_port_setup_targets(iter, cxlr, cxled);
> +			rc = cxl_switch_port_setup_targets(iter, cxlr, cxled);
>   			if (rc) {
>   				cxl_region_teardown_targets(cxlr);
>   				return rc;

Re: [PATCH v3 3/7] cxl/region: Factor out cxl_port_peer_distance()

[Li Ming]

在 2026/10/13 12:25, Alison Schofield 写道:
> cxl_switch_port_setup_targets() is nearly 200 lines long and open codes
> each step of adding an endpoint to a port's decoder. One of those steps
> calculates the distance between region positions that share a downstream
> port.
>
> Move that calculation to a new helper, cxl_port_peer_distance().
>
> No functional change.
>
> Assisted-by: LLM
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>

> ---
>   drivers/cxl/core/region.c | 50 +++++++++++++++++++++++----------------
>   1 file changed, 29 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 9b0e2f195d1f..ea281ce4ec49 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1432,6 +1432,33 @@ static int check_interleave_cap(struct cxl_decoder *cxld, int iw, int ig)
>   	return 0;
>   }
>   
> +/*
> + * The "distance" between peer downstream ports represents which
> + * endpoint positions in the region interleave a given port can
> + * host.
> + *
> + * For example, at the root of a hierarchy the distance is
> + * always 1 as every index targets a different host-bridge. At
> + * each subsequent switch level those ports map every Nth region
> + * position where N is the width of the switch == distance.
> + */
> +static int cxl_port_peer_distance(struct cxl_port *port, struct cxl_region *cxlr)
> +{
> +	struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
> +	struct cxl_region_ref *cxl_rr_iter;
> +	struct cxl_port *iter = port;
> +	int distance = 1;
> +
> +	do {
> +		cxl_rr_iter = cxl_rr_load(iter, cxlr);
> +		distance *= cxl_rr_iter->nr_targets;
> +		iter = to_cxl_port(iter->dev.parent);
> +	} while (!is_cxl_root(iter));
> +	distance *= cxlrd->cxlsd.cxld.interleave_ways;
> +
> +	return distance;
> +}
> +
>   static int cxl_switch_port_setup_targets(struct cxl_port *port,
>   					 struct cxl_region *cxlr,
>   					 struct cxl_endpoint_decoder *cxled)
> @@ -1445,7 +1472,6 @@ static int cxl_switch_port_setup_targets(struct cxl_port *port,
>   	struct cxl_region_params *p = &cxlr->params;
>   	struct cxl_decoder *cxld = cxl_rr->decoder;
>   	struct cxl_switch_decoder *cxlsd;
> -	struct cxl_port *iter = port;
>   
>   	/*
>   	 * While root level decoders support x3, x6, x12, switch level
> @@ -1460,27 +1486,9 @@ static int cxl_switch_port_setup_targets(struct cxl_port *port,
>   
>   	cxlsd = to_cxl_switch_decoder(&cxld->dev);
>   	if (cxl_rr->nr_targets_set) {
> -		int i, distance = 1;
> -		struct cxl_region_ref *cxl_rr_iter;
> +		int distance = cxl_port_peer_distance(port, cxlr);
>   
> -		/*
> -		 * The "distance" between peer downstream ports represents which
> -		 * endpoint positions in the region interleave a given port can
> -		 * host.
> -		 *
> -		 * For example, at the root of a hierarchy the distance is
> -		 * always 1 as every index targets a different host-bridge. At
> -		 * each subsequent switch level those ports map every Nth region
> -		 * position where N is the width of the switch == distance.
> -		 */
> -		do {
> -			cxl_rr_iter = cxl_rr_load(iter, cxlr);
> -			distance *= cxl_rr_iter->nr_targets;
> -			iter = to_cxl_port(iter->dev.parent);
> -		} while (!is_cxl_root(iter));
> -		distance *= cxlrd->cxlsd.cxld.interleave_ways;
> -
> -		for (i = 0; i < cxl_rr->nr_targets_set; i++)
> +		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
>   			if (ep->dport == cxlsd->target[i]) {
>   				rc = check_last_peer(cxled, ep, cxl_rr,
>   						     distance);

Re: [PATCH v3 7/7] cxl/region: Factor out cxl_switch_port_add_target()

[Li Ming]

在 2026/10/13 12:26, Alison Schofield 写道:
> cxl_switch_port_setup_targets() adds an endpoint's downstream port to a
> port's decoder target list. For an auto region it checks that the decoder
> already targets that downstream port at the next position. For a user
> created region it programs the downstream port at that position. That step
> is open coded behind an add_target label that the target search jumps to.
>
> Move that step to a new helper, cxl_switch_port_add_target(). The helper
> takes the switch decoder whose target list it updates, rather than the
> port, which makes its scope explicit. With the decoder setup and the
> target add now in helpers, the path for the first endpoint to reach a port
> becomes an else branch of the target search, so the add_target label is
> no longer needed.
>
> No functional change.
>
> Assisted-by: LLM
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>


Just one minor comment below.

> ---
>   drivers/cxl/core/region.c | 80 ++++++++++++++++++++++++---------------
>   1 file changed, 49 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 229372123271..50f4830c225d 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1608,15 +1608,50 @@ static int cxl_port_setup_decoder(struct cxl_port *port, struct cxl_region *cxlr
>   	return 0;
>   }
>   
> +static int cxl_switch_port_add_target(struct cxl_switch_decoder *cxlsd,
> +				      struct cxl_region *cxlr,
> +				      struct cxl_region_ref *cxl_rr,
> +				      struct cxl_endpoint_decoder *cxled,
> +				      struct cxl_ep *ep)
> +{
> +	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> +	struct cxl_port *port = cxl_rr->port;
> +	int pos = cxled->pos;
> +
> +	if (cxl_rr->nr_targets_set == cxl_rr->nr_targets) {
> +		dev_dbg(&cxlr->dev,
> +			"%s:%s: targets full trying to add %s:%s at %d\n",
> +			dev_name(port->uport_dev), dev_name(&port->dev),
> +			dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev), pos);
> +		return -ENXIO;
> +	}
> +	if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags)) {
> +		if (cxlsd->target[cxl_rr->nr_targets_set] != ep->dport) {
> +			dev_dbg(&cxlr->dev, "%s:%s: %s expected %s at %d\n",
> +				dev_name(port->uport_dev), dev_name(&port->dev),
> +				dev_name(&cxlsd->cxld.dev),
> +				dev_name(ep->dport->dport_dev),
> +				cxl_rr->nr_targets_set);
> +			return -ENXIO;
> +		}
> +	} else {
> +		cxlsd->target[cxl_rr->nr_targets_set] = ep->dport;
> +		cxlsd->cxld.target_map[cxl_rr->nr_targets_set] = ep->dport->port_id;
> +	}
> +	cxl_rr->nr_targets_set++;
> +
> +	return 0;
> +}
> +
>   static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_region *cxlr,
>   					 struct cxl_endpoint_decoder *cxled)
>   {
> -	int iw, ig, rc, pos = cxled->pos;
>   	struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
>   	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
>   	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
>   	struct cxl_decoder *cxld = cxl_rr->decoder;
>   	struct cxl_switch_decoder *cxlsd;
> +	int rc, pos = cxled->pos;
>   
>   	/*
>   	 * While root level decoders support x3, x6, x12, switch level
> @@ -1641,38 +1676,21 @@ static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_regio
>   					return rc;
>   				goto out_target_set;
>   			}
> -		goto add_target;
> -	}
> -
> -	rc = cxl_port_calc_interleave(port, cxlr, cxl_rr, &iw, &ig);
> -	if (rc)
> -		return rc;
> -
> -	rc = cxl_port_setup_decoder(port, cxlr, cxld, iw, ig);
> -	if (rc)
> -		return rc;
> -add_target:
> -	if (cxl_rr->nr_targets_set == cxl_rr->nr_targets) {
> -		dev_dbg(&cxlr->dev,
> -			"%s:%s: targets full trying to add %s:%s at %d\n",
> -			dev_name(port->uport_dev), dev_name(&port->dev),
> -			dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev), pos);
> -		return -ENXIO;
> -	}
> -	if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags)) {
> -		if (cxlsd->target[cxl_rr->nr_targets_set] != ep->dport) {
> -			dev_dbg(&cxlr->dev, "%s:%s: %s expected %s at %d\n",
> -				dev_name(port->uport_dev), dev_name(&port->dev),
> -				dev_name(&cxlsd->cxld.dev),
> -				dev_name(ep->dport->dport_dev),
> -				cxl_rr->nr_targets_set);
> -			return -ENXIO;
> -		}
>   	} else {
> -		cxlsd->target[cxl_rr->nr_targets_set] = ep->dport;
> -		cxlsd->cxld.target_map[cxl_rr->nr_targets_set] = ep->dport->port_id;
> +		int iw, ig;
> +
> +		rc = cxl_port_calc_interleave(port, cxlr, cxl_rr, &iw, &ig);
> +		if (rc)
> +			return rc;
> +
> +		rc = cxl_port_setup_decoder(port, cxlr, cxld, iw, ig);
> +		if (rc)
> +			return rc;
>   	}
> -	cxl_rr->nr_targets_set++;
> +
> +	rc = cxl_switch_port_add_target(cxlsd, cxlr, cxl_rr, cxled, ep);
> +	if (rc)
> +		return rc;
>   out_target_set:
Do we really need this "out_target_set"? Seems like it can be removed 
too. Once a new target is set up, this function outputs the following 
log, if this function finds a registered target, I guess we don't need 
to output the following log again?
>   	dev_dbg(&cxlr->dev, "%s:%s target[%d] = %s for %s:%s @ %d\n",
>   		dev_name(port->uport_dev), dev_name(&port->dev),

Re: [PATCH v3 4/7] cxl/region: Factor out cxl_port_parent_interleave()

[Li Ming]

在 2026/10/13 12:26, Alison Schofield 写道:
> cxl_switch_port_setup_targets() derives a decoder's interleave from the
> interleave of the decoder above it. That parent interleave comes from
> either the root decoder or a switch decoder, and each case is open coded
> along with the parent validity checks.
>
> Move the parent interleave lookup and validation to a new helper,
> cxl_port_parent_interleave().
>
> No functional change.
>
> Assisted-by: LLM
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>
> ---
>   drivers/cxl/core/region.c | 88 +++++++++++++++++++++++----------------
>   1 file changed, 52 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index ea281ce4ec49..c14ac041c4ac 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1459,45 +1459,13 @@ static int cxl_port_peer_distance(struct cxl_port *port, struct cxl_region *cxlr
>   	return distance;
>   }
>   
> -static int cxl_switch_port_setup_targets(struct cxl_port *port,
> -					 struct cxl_region *cxlr,
> -					 struct cxl_endpoint_decoder *cxled)
> +static int cxl_port_parent_interleave(struct cxl_port *port, struct cxl_region *cxlr,
> +				      int *out_iw, int *out_ig)
>   {
> -	struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
> -	int parent_iw, parent_ig, ig, iw, rc, pos = cxled->pos;
>   	struct cxl_port *parent_port = to_cxl_port(port->dev.parent);
> -	struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
> -	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> -	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
> +	struct cxl_root_decoder *cxlrd = cxlr->cxlrd;
>   	struct cxl_region_params *p = &cxlr->params;
> -	struct cxl_decoder *cxld = cxl_rr->decoder;
> -	struct cxl_switch_decoder *cxlsd;
> -
> -	/*
> -	 * While root level decoders support x3, x6, x12, switch level
> -	 * decoders only support powers of 2 up to x16.
> -	 */
> -	if (!is_power_of_2(cxl_rr->nr_targets)) {
> -		dev_dbg(&cxlr->dev, "%s:%s: invalid target count %d\n",
> -			dev_name(port->uport_dev), dev_name(&port->dev),
> -			cxl_rr->nr_targets);
> -		return -EINVAL;
> -	}
> -
> -	cxlsd = to_cxl_switch_decoder(&cxld->dev);
> -	if (cxl_rr->nr_targets_set) {
> -		int distance = cxl_port_peer_distance(port, cxlr);
> -
> -		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
> -			if (ep->dport == cxlsd->target[i]) {
> -				rc = check_last_peer(cxled, ep, cxl_rr,
> -						     distance);
> -				if (rc)
> -					return rc;
> -				goto out_target_set;
> -			}
> -		goto add_target;
> -	}
> +	int parent_iw, parent_ig;
>   
>   	if (is_cxl_root(parent_port)) {
>   		/*
> @@ -1539,6 +1507,54 @@ static int cxl_switch_port_setup_targets(struct cxl_port *port,
>   		return -EINVAL;
>   	}
>   
> +	*out_iw = parent_iw;
> +	*out_ig = parent_ig;
> +
> +	return 0;
> +}
> +
> +static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_region *cxlr,
> +					 struct cxl_endpoint_decoder *cxled)
> +{
> +	int parent_iw, parent_ig, ig, iw, rc, pos = cxled->pos;
> +	struct cxl_port *parent_port = to_cxl_port(port->dev.parent);
> +	struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
> +	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> +	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
> +	struct cxl_region_params *p = &cxlr->params;
> +	struct cxl_decoder *cxld = cxl_rr->decoder;
> +	struct cxl_switch_decoder *cxlsd;
> +
> +	/*
> +	 * While root level decoders support x3, x6, x12, switch level
> +	 * decoders only support powers of 2 up to x16.
> +	 */
> +	if (!is_power_of_2(cxl_rr->nr_targets)) {
> +		dev_dbg(&cxlr->dev, "%s:%s: invalid target count %d\n",
> +			dev_name(port->uport_dev), dev_name(&port->dev),
> +			cxl_rr->nr_targets);
> +		return -EINVAL;
> +	}
> +
> +	cxlsd = to_cxl_switch_decoder(&cxld->dev);
> +	if (cxl_rr->nr_targets_set) {
> +		int distance = cxl_port_peer_distance(port, cxlr);
> +
> +		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
> +			if (ep->dport == cxlsd->target[i]) {
> +				rc = check_last_peer(cxled, ep, cxl_rr,
> +						     distance);
> +				if (rc)
> +					return rc;
> +				goto out_target_set;
> +			}
> +		goto add_target;
> +	}
> +
> +	rc = cxl_port_parent_interleave(port, cxlr, &parent_iw, &parent_ig);
> +	if (rc)
> +		return rc;
> +
>   	iw = cxl_rr->nr_targets;
>   	if (!ways_valid(iw)) {
>   		dev_dbg(&cxlr->dev, "%s:%s: invalid port interleave: %d\n",

Re: [PATCH v3 5/7] cxl/region: Factor out cxl_port_calc_interleave()

[Li Ming]

在 2026/10/13 12:26, Alison Schofield 写道:
> cxl_switch_port_setup_targets() calculates the interleave ways and
> granularity of a port's decoder from the parent interleave and the number
> of targets below the port, then validates the result. That calculation and
> its checks are open coded between the target search and the decoder setup.
>
> Move the calculation and its checks to a new helper,
> cxl_port_calc_interleave(), so that the interleave for the port's decoder
> is calculated and validated in one place.
>
> No functional change.
>
> Assisted-by: LLM
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>

> ---
>   drivers/cxl/core/region.c | 81 ++++++++++++++++++++++++---------------
>   1 file changed, 50 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index c14ac041c4ac..ee9e615a9a4c 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1513,11 +1513,58 @@ static int cxl_port_parent_interleave(struct cxl_port *port, struct cxl_region *
>   	return 0;
>   }
>   
> +static int cxl_port_calc_interleave(struct cxl_port *port, struct cxl_region *cxlr,
> +				    struct cxl_region_ref *cxl_rr, int *out_iw,
> +				    int *out_ig)
> +{
> +	struct cxl_port *parent_port = to_cxl_port(port->dev.parent);
> +	struct cxl_decoder *cxld = cxl_rr->decoder;
> +	int parent_iw, parent_ig, iw, ig, rc;
> +	struct cxl_switch_decoder *cxlsd;
> +
> +	rc = cxl_port_parent_interleave(port, cxlr, &parent_iw, &parent_ig);
> +	if (rc)
> +		return rc;
> +
> +	iw = cxl_rr->nr_targets;
> +	if (!ways_valid(iw)) {
> +		dev_dbg(&cxlr->dev, "%s:%s: invalid port interleave: %d\n",
> +			dev_name(port->uport_dev), dev_name(&port->dev), iw);
> +		return -EINVAL;
> +	}
> +
> +	/*
> +	 * Interleave granularity is a multiple of @parent_port granularity.
> +	 * Multiplier is the parent port interleave ways.
> +	 */
> +	ig = parent_ig * parent_iw;
> +
> +	if (!granularity_valid(ig)) {
> +		dev_dbg(&cxlr->dev,
> +			"%s: invalid granularity calculation (%d * %d)\n",
> +			dev_name(&parent_port->dev), parent_ig, parent_iw);
> +		return -EINVAL;
> +	}
> +
> +	cxlsd = to_cxl_switch_decoder(&cxld->dev);
> +	if (iw > 8 || iw > cxlsd->nr_targets) {
> +		dev_dbg(&cxlr->dev,
> +			"%s:%s:%s: ways: %d overflows targets: %d\n",
> +			dev_name(port->uport_dev), dev_name(&port->dev),
> +			dev_name(&cxld->dev), iw, cxlsd->nr_targets);
> +		return -ENXIO;
> +	}
> +
> +	*out_iw = iw;
> +	*out_ig = ig;
> +
> +	return 0;
> +}
> +
>   static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_region *cxlr,
>   					 struct cxl_endpoint_decoder *cxled)
>   {
> -	int parent_iw, parent_ig, ig, iw, rc, pos = cxled->pos;
> -	struct cxl_port *parent_port = to_cxl_port(port->dev.parent);
> +	int iw, ig, rc, pos = cxled->pos;
>   	struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
>   	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
>   	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
> @@ -1551,38 +1598,10 @@ static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_regio
>   		goto add_target;
>   	}
>   
> -	rc = cxl_port_parent_interleave(port, cxlr, &parent_iw, &parent_ig);
> +	rc = cxl_port_calc_interleave(port, cxlr, cxl_rr, &iw, &ig);
>   	if (rc)
>   		return rc;
>   
> -	iw = cxl_rr->nr_targets;
> -	if (!ways_valid(iw)) {
> -		dev_dbg(&cxlr->dev, "%s:%s: invalid port interleave: %d\n",
> -			dev_name(port->uport_dev), dev_name(&port->dev), iw);
> -		return -EINVAL;
> -	}
> -
> -	/*
> -	 * Interleave granularity is a multiple of @parent_port granularity.
> -	 * Multiplier is the parent port interleave ways.
> -	 */
> -	ig = parent_ig * parent_iw;
> -
> -	if (!granularity_valid(ig)) {
> -		dev_dbg(&cxlr->dev,
> -			"%s: invalid granularity calculation (%d * %d)\n",
> -			dev_name(&parent_port->dev), parent_ig, parent_iw);
> -		return -EINVAL;
> -	}
> -
> -	if (iw > 8 || iw > cxlsd->nr_targets) {
> -		dev_dbg(&cxlr->dev,
> -			"%s:%s:%s: ways: %d overflows targets: %d\n",
> -			dev_name(port->uport_dev), dev_name(&port->dev),
> -			dev_name(&cxld->dev), iw, cxlsd->nr_targets);
> -		return -ENXIO;
> -	}
> -
>   	if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags)) {
>   		if (cxld->interleave_ways != iw ||
>   		    (iw > 1 && cxld->interleave_granularity != ig) ||

Re: [PATCH v3 6/7] cxl/region: Factor out cxl_port_setup_decoder()

[Li Ming]

在 2026/10/13 12:26, Alison Schofield 写道:
> Once cxl_switch_port_setup_targets() has calculated the interleave for a
> port's decoder, it either checks that interleave against the decoder
> settings found for an auto region, or checks the decoder's interleave
> capabilities and programs the decoder for a user created region. Both paths
> are open coded in cxl_switch_port_setup_targets().
>
> Move both paths to a new helper, cxl_port_setup_decoder().
>
> No functional change.
>
> Assisted-by: LLM
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>


See my comment in patch #7.

> ---
>   drivers/cxl/core/region.c | 88 ++++++++++++++++++++++-----------------
>   1 file changed, 50 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index ee9e615a9a4c..229372123271 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1561,46 +1561,11 @@ static int cxl_port_calc_interleave(struct cxl_port *port, struct cxl_region *cx
>   	return 0;
>   }
>   
> -static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_region *cxlr,
> -					 struct cxl_endpoint_decoder *cxled)
> +static int cxl_port_setup_decoder(struct cxl_port *port, struct cxl_region *cxlr,
> +				  struct cxl_decoder *cxld, int iw, int ig)
>   {
> -	int iw, ig, rc, pos = cxled->pos;
> -	struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
> -	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> -	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
>   	struct cxl_region_params *p = &cxlr->params;
> -	struct cxl_decoder *cxld = cxl_rr->decoder;
> -	struct cxl_switch_decoder *cxlsd;
> -
> -	/*
> -	 * While root level decoders support x3, x6, x12, switch level
> -	 * decoders only support powers of 2 up to x16.
> -	 */
> -	if (!is_power_of_2(cxl_rr->nr_targets)) {
> -		dev_dbg(&cxlr->dev, "%s:%s: invalid target count %d\n",
> -			dev_name(port->uport_dev), dev_name(&port->dev),
> -			cxl_rr->nr_targets);
> -		return -EINVAL;
> -	}
> -
> -	cxlsd = to_cxl_switch_decoder(&cxld->dev);
> -	if (cxl_rr->nr_targets_set) {
> -		int distance = cxl_port_peer_distance(port, cxlr);
> -
> -		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
> -			if (ep->dport == cxlsd->target[i]) {
> -				rc = check_last_peer(cxled, ep, cxl_rr,
> -						     distance);
> -				if (rc)
> -					return rc;
> -				goto out_target_set;
> -			}
> -		goto add_target;
> -	}
> -
> -	rc = cxl_port_calc_interleave(port, cxlr, cxl_rr, &iw, &ig);
> -	if (rc)
> -		return rc;
> +	int rc;
>   
>   	if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags)) {
>   		if (cxld->interleave_ways != iw ||
> @@ -1639,6 +1604,53 @@ static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_regio
>   	}
>   	dev_dbg(&cxlr->dev, "%s:%s iw: %d ig: %d\n", dev_name(port->uport_dev),
>   		dev_name(&port->dev), iw, ig);
> +
> +	return 0;
> +}
> +
> +static int cxl_switch_port_setup_targets(struct cxl_port *port, struct cxl_region *cxlr,
> +					 struct cxl_endpoint_decoder *cxled)
> +{
> +	int iw, ig, rc, pos = cxled->pos;
> +	struct cxl_region_ref *cxl_rr = cxl_rr_load(port, cxlr);
> +	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> +	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
> +	struct cxl_decoder *cxld = cxl_rr->decoder;
> +	struct cxl_switch_decoder *cxlsd;
> +
> +	/*
> +	 * While root level decoders support x3, x6, x12, switch level
> +	 * decoders only support powers of 2 up to x16.
> +	 */
> +	if (!is_power_of_2(cxl_rr->nr_targets)) {
> +		dev_dbg(&cxlr->dev, "%s:%s: invalid target count %d\n",
> +			dev_name(port->uport_dev), dev_name(&port->dev),
> +			cxl_rr->nr_targets);
> +		return -EINVAL;
> +	}
> +
> +	cxlsd = to_cxl_switch_decoder(&cxld->dev);
> +	if (cxl_rr->nr_targets_set) {
> +		int distance = cxl_port_peer_distance(port, cxlr);
> +
> +		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
> +			if (ep->dport == cxlsd->target[i]) {
> +				rc = check_last_peer(cxled, ep, cxl_rr,
> +						     distance);
> +				if (rc)
> +					return rc;
> +				goto out_target_set;
> +			}
> +		goto add_target;
> +	}
> +
> +	rc = cxl_port_calc_interleave(port, cxlr, cxl_rr, &iw, &ig);
> +	if (rc)
> +		return rc;
> +
> +	rc = cxl_port_setup_decoder(port, cxlr, cxld, iw, ig);
> +	if (rc)
> +		return rc;
>   add_target:
>   	if (cxl_rr->nr_targets_set == cxl_rr->nr_targets) {
>   		dev_dbg(&cxlr->dev,