[PATCH v5 0/9] cxl/region: Refactor cxl_port_setup_targets()

[PATCH v5 0/9] cxl/region: Refactor cxl_port_setup_targets()

[Alison Schofield]

Changes in v5:
- Update patch 4 commit message w test result & benefit info (RichardC)
- Rebase on 7.4-rc1
v4: https://lore.kernel.org/all/cover.1792263750.git.alison.schofield@intel.com/

Changes in v4:
- Pass cxlsd to cxl_switch_port_setup_targets() (DaveJ)
- New Patch 4 from Richard, only calc peer distance on target reuse (RichardC)
- Add function comment to cxl_port_parent_interleave() (RichardC)
- New Patch 8 simplifies control flow (MingL, JonathanC)
- Remove claim in cover letter of a strictly mechanical refactor
- Drop LLM tags per latest guidance
v3: https://lore.kernel.org/linux-cxl/cover.1791860305.git.alison.schofield@intel.com/

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, and changes its parameter to accept a
switch decoder rather than a port, both DaveJ suggestions.

Patches 3-9 extract the individual steps into helpers and add two new patches:
RichardC's patch 4 avoids calculating peer distance when an endpoint adds a
new target, and patch 8, suggested by Ming and Jonathan, removes the goto paths
before the final helper is extracted.

The result reduces cxl_switch_port_setup_targets() to 53 lines.

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


Alison Schofield (8):
  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: Simplify switch port target setup control flow
  cxl/region: Factor out cxl_switch_port_add_target()

Richard Cheng (1):
  cxl/region: Calculate peer distance only for reused targets

 drivers/cxl/core/region.c | 243 +++++++++++++++++++++++---------------
 drivers/cxl/cxl.h         |  21 ++++
 2 files changed, 172 insertions(+), 92 deletions(-)


base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
-- 
2.37.3

[PATCH v5 1/9] 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>
Reviewed-by: Richard Cheng <icheng@nvidia.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 baa6df2d362a..11688d17d09f 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 v5 2/9] 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 and pass it the switch decoder so the parameter type enforces
that scope.

No functional change.

Suggested-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Reviewed-by: Richard Cheng <icheng@nvidia.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>
---
 drivers/cxl/core/region.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index bc087ca63946..6ce27b8b63be 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1432,10 +1432,11 @@ 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_switch_decoder *cxlsd,
+					 struct cxl_region *cxlr,
+					 struct cxl_endpoint_decoder *cxled)
 {
+	struct cxl_port *port = to_cxl_port(cxlsd->cxld.dev.parent);
 	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);
@@ -1443,8 +1444,7 @@ static int cxl_port_setup_targets(struct cxl_port *port,
 	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;
+	struct cxl_decoder *cxld = &cxlsd->cxld;
 	struct cxl_port *iter = port;
 
 	/*
@@ -1458,7 +1458,6 @@ static int cxl_port_setup_targets(struct cxl_port *port,
 		return -EINVAL;
 	}
 
-	cxlsd = to_cxl_switch_decoder(&cxld->dev);
 	if (cxl_rr->nr_targets_set) {
 		int i, distance = 1;
 		struct cxl_region_ref *cxl_rr_iter;
@@ -1716,7 +1715,11 @@ 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);
+			struct cxl_region_ref *cxl_rr = cxl_rr_load(iter, cxlr);
+			struct cxl_switch_decoder *cxlsd;
+
+			cxlsd = to_cxl_switch_decoder(&cxl_rr->decoder->dev);
+			rc = cxl_switch_port_setup_targets(cxlsd, cxlr, cxled);
 			if (rc) {
 				cxl_region_teardown_targets(cxlr);
 				return rc;
-- 
2.37.3

[PATCH v5 3/9] 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.

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: Richard Cheng <icheng@nvidia.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 6ce27b8b63be..4ab5a1d025a9 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_switch_decoder *cxlsd,
 					 struct cxl_region *cxlr,
 					 struct cxl_endpoint_decoder *cxled)
@@ -1445,7 +1472,6 @@ static int cxl_switch_port_setup_targets(struct cxl_switch_decoder *cxlsd,
 	struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
 	struct cxl_region_params *p = &cxlr->params;
 	struct cxl_decoder *cxld = &cxlsd->cxld;
-	struct cxl_port *iter = port;
 
 	/*
 	 * While root level decoders support x3, x6, x12, switch level
@@ -1459,27 +1485,9 @@ static int cxl_switch_port_setup_targets(struct cxl_switch_decoder *cxlsd,
 	}
 
 	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 v5 4/9] cxl/region: Calculate peer distance only for reused targets

[Alison Schofield]

From: Richard Cheng <icheng@nvidia.com>

cxl_switch_port_setup_targets() calculates peer distance before
searching the existing targets. When the endpoint needs a new target,
the calculated distance is never used.

Move cxl_port_peer_distance() into the matching-target branch,
immediately before check_last_peer(). This avoids unnecessary ancestor
walks and per-port region lookups when adding distinct targets.

With cxl_test, the x8 region in cxl-region-sysfs.sh reduces calls to
cxl_port_peer_distance() from 10 to 4, and the x2 auto region from 2
to 1. A misordered-endpoint test confirms that peer validation still
rejects mismatched peers.

Signed-off-by: Richard Cheng <icheng@nvidia.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---
 drivers/cxl/core/region.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 4ab5a1d025a9..8bfebe3e1025 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1485,10 +1485,10 @@ static int cxl_switch_port_setup_targets(struct cxl_switch_decoder *cxlsd,
 	}
 
 	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]) {
+				int distance = cxl_port_peer_distance(port, cxlr);
+
 				rc = check_last_peer(cxled, ep, cxl_rr,
 						     distance);
 				if (rc)
-- 
2.37.3

[PATCH v5 5/9] 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.

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Reviewed-by: Richard Cheng <icheng@nvidia.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>
---
 drivers/cxl/core/region.c | 99 ++++++++++++++++++++++++---------------
 1 file changed, 60 insertions(+), 39 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 8bfebe3e1025..cdf90fb6ea64 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1459,44 +1459,21 @@ 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_switch_decoder *cxlsd,
-					 struct cxl_region *cxlr,
-					 struct cxl_endpoint_decoder *cxled)
+/*
+ * Get the parent interleave ways and granularity.
+ *
+ * For address bit routing, use power-of-2 math for switch ports.
+ * Root interleave ways of 3, 6, or 12 are normalized to 1, 2, or 4
+ * in @out_iw.
+ */
+static int cxl_port_parent_interleave(struct cxl_port *port,
+				      struct cxl_region *cxlr,
+				      int *out_iw, int *out_ig)
 {
-	struct cxl_port *port = to_cxl_port(cxlsd->cxld.dev.parent);
-	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 = &cxlsd->cxld;
-
-	/*
-	 * 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;
-	}
-
-	if (cxl_rr->nr_targets_set) {
-		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
-			if (ep->dport == cxlsd->target[i]) {
-				int distance = cxl_port_peer_distance(port, cxlr);
-
-				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)) {
 		/*
@@ -1508,10 +1485,6 @@ static int cxl_switch_port_setup_targets(struct cxl_switch_decoder *cxlsd,
 		 */
 		parent_ig = p->interleave_granularity;
 		parent_iw = cxlrd->cxlsd.cxld.interleave_ways;
-		/*
-		 * For purposes of address bit routing, use power-of-2 math for
-		 * switch ports.
-		 */
 		if (!is_power_of_2(parent_iw))
 			parent_iw /= 3;
 	} else {
@@ -1538,6 +1511,54 @@ static int cxl_switch_port_setup_targets(struct cxl_switch_decoder *cxlsd,
 		return -EINVAL;
 	}
 
+	*out_iw = parent_iw;
+	*out_ig = parent_ig;
+
+	return 0;
+}
+
+static int cxl_switch_port_setup_targets(struct cxl_switch_decoder *cxlsd,
+					 struct cxl_region *cxlr,
+					 struct cxl_endpoint_decoder *cxled)
+{
+	struct cxl_port *port = to_cxl_port(cxlsd->cxld.dev.parent);
+	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 = &cxlsd->cxld;
+
+	/*
+	 * 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;
+	}
+
+	if (cxl_rr->nr_targets_set) {
+		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
+			if (ep->dport == cxlsd->target[i]) {
+				int distance = cxl_port_peer_distance(port, cxlr);
+
+				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 v5 6/9] 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.

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: Richard Cheng <icheng@nvidia.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 cdf90fb6ea64..d25df041e922 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1517,13 +1517,60 @@ static int cxl_port_parent_interleave(struct cxl_port *port,
 	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_switch_decoder *cxlsd,
 					 struct cxl_region *cxlr,
 					 struct cxl_endpoint_decoder *cxled)
 {
 	struct cxl_port *port = to_cxl_port(cxlsd->cxld.dev.parent);
-	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);
@@ -1555,38 +1602,10 @@ static int cxl_switch_port_setup_targets(struct cxl_switch_decoder *cxlsd,
 		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 v5 7/9] 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.

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 | 88 ++++++++++++++++++++++-----------------
 1 file changed, 50 insertions(+), 38 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index d25df041e922..025cf21adfa9 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1565,46 +1565,11 @@ 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_switch_decoder *cxlsd,
-					 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)
 {
-	struct cxl_port *port = to_cxl_port(cxlsd->cxld.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);
 	struct cxl_region_params *p = &cxlr->params;
-	struct cxl_decoder *cxld = &cxlsd->cxld;
-
-	/*
-	 * 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;
-	}
-
-	if (cxl_rr->nr_targets_set) {
-		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
-			if (ep->dport == cxlsd->target[i]) {
-				int distance = cxl_port_peer_distance(port, cxlr);
-
-				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 ||
@@ -1643,6 +1608,53 @@ static int cxl_switch_port_setup_targets(struct cxl_switch_decoder *cxlsd,
 	}
 	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_switch_decoder *cxlsd,
+					 struct cxl_region *cxlr,
+					 struct cxl_endpoint_decoder *cxled)
+{
+	struct cxl_port *port = to_cxl_port(cxlsd->cxld.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);
+	struct cxl_decoder *cxld = &cxlsd->cxld;
+
+	/*
+	 * 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;
+	}
+
+	if (cxl_rr->nr_targets_set) {
+		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
+			if (ep->dport == cxlsd->target[i]) {
+				int distance = cxl_port_peer_distance(port, cxlr);
+
+				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 v5 8/9] cxl/region: Simplify switch port target setup control flow

[Alison Schofield]

cxl_switch_port_setup_targets() searches the decoder's existing targets
for the endpoint's downstream port. On a match it checks the peer position
and jumps to an out_target_set label to log the target. Otherwise it jumps
to an add_target label, skipping the interleave calculation and decoder
setup that only the first endpoint to reach a port needs.

Return the peer check result directly when the downstream port is already
a target, and make the first endpoint's decoder setup the else branch of
the target search. Both labels go away.

Returning directly after peer validation also removes a misleading debug
message that reported a reused target as a new assignment, with a bad
index.

Suggested-by: Li Ming <ming.li@zohomail.com>
Suggested-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---
 drivers/cxl/core/region.c | 34 +++++++++++++++-------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 025cf21adfa9..2a64ecf656b7 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1635,27 +1635,23 @@ static int cxl_switch_port_setup_targets(struct cxl_switch_decoder *cxlsd,
 	}
 
 	if (cxl_rr->nr_targets_set) {
-		for (int i = 0; i < cxl_rr->nr_targets_set; i++)
-			if (ep->dport == cxlsd->target[i]) {
-				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])
+				continue;
 
-				rc = check_last_peer(cxled, ep, cxl_rr,
-						     distance);
-				if (rc)
-					return rc;
-				goto out_target_set;
-			}
-		goto add_target;
+			return check_last_peer(cxled, ep, cxl_rr,
+					       cxl_port_peer_distance(port, cxlr));
+		}
+	} else {
+		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;
 	}
 
-	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",
@@ -1677,7 +1673,7 @@ static int cxl_switch_port_setup_targets(struct cxl_switch_decoder *cxlsd,
 		cxlsd->cxld.target_map[cxl_rr->nr_targets_set] = ep->dport->port_id;
 	}
 	cxl_rr->nr_targets_set++;
-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),
 		cxl_rr->nr_targets_set - 1, dev_name(ep->dport->dport_dev),
-- 
2.37.3

[PATCH v5 9/9] 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.

Move that step to a new helper, cxl_switch_port_add_target(). The helper
takes the switch decoder whose target list it updates, which makes the
scope explicit.

No functional change.

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Richard Cheng <icheng@nvidia.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>
---
 drivers/cxl/core/region.c | 59 +++++++++++++++++++++++++--------------
 1 file changed, 38 insertions(+), 21 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 2a64ecf656b7..d6a5dbe65d26 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1612,6 +1612,41 @@ 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_switch_decoder *cxlsd,
 					 struct cxl_region *cxlr,
 					 struct cxl_endpoint_decoder *cxled)
@@ -1652,27 +1687,9 @@ static int cxl_switch_port_setup_targets(struct cxl_switch_decoder *cxlsd,
 			return rc;
 	}
 
-	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++;
+	rc = cxl_switch_port_add_target(cxlsd, cxlr, cxl_rr, cxled, ep);
+	if (rc)
+		return rc;
 
 	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 v5 0/9] cxl/region: Refactor cxl_port_setup_targets()

[Dave Jiang]

On 11/2/26 1:15 PM, Alison Schofield wrote:
> 
> Changes in v5:
> - Update patch 4 commit message w test result & benefit info (RichardC)
> - Rebase on 7.4-rc1
> v4: https://lore.kernel.org/all/cover.1792263750.git.alison.schofield@intel.com/
> 
> Changes in v4:
> - Pass cxlsd to cxl_switch_port_setup_targets() (DaveJ)
> - New Patch 4 from Richard, only calc peer distance on target reuse (RichardC)
> - Add function comment to cxl_port_parent_interleave() (RichardC)
> - New Patch 8 simplifies control flow (MingL, JonathanC)
> - Remove claim in cover letter of a strictly mechanical refactor
> - Drop LLM tags per latest guidance
> v3: https://lore.kernel.org/linux-cxl/cover.1791860305.git.alison.schofield@intel.com/
> 
> 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, and changes its parameter to accept a
> switch decoder rather than a port, both DaveJ suggestions.
> 
> Patches 3-9 extract the individual steps into helpers and add two new patches:
> RichardC's patch 4 avoids calculating peer distance when an endpoint adds a
> new target, and patch 8, suggested by Ming and Jonathan, removes the goto paths
> before the final helper is extracted.
> 
> The result reduces cxl_switch_port_setup_targets() to 53 lines.
> 
> [1] https://lore.kernel.org/linux-cxl/cover.1788475206.git.alison.schofield@intel.com/
> 
> 
> Alison Schofield (8):
>   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: Simplify switch port target setup control flow
>   cxl/region: Factor out cxl_switch_port_add_target()
> 
> Richard Cheng (1):
>   cxl/region: Calculate peer distance only for reused targets
> 
>  drivers/cxl/core/region.c | 243 +++++++++++++++++++++++---------------
>  drivers/cxl/cxl.h         |  21 ++++
>  2 files changed, 172 insertions(+), 92 deletions(-)
> 
> 
> base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4

Applied to cxl/next:
0e3e8b653ca3 cxl/region: Factor out cxl_switch_port_add_target()
127ea4404a12 cxl/region: Simplify switch port target setup control flow
a8aaec84078b cxl/region: Factor out cxl_port_setup_decoder()
e2720e46d4ed cxl/region: Factor out cxl_port_calc_interleave()
96a2f5773a27 cxl/region: Factor out cxl_port_parent_interleave()
dfa9daea3c00 cxl/region: Calculate peer distance only for reused targets
88262ac09371 cxl/region: Factor out cxl_port_peer_distance()
d523a24a97c4 cxl/region: Rename cxl_port_setup_targets() to cxl_switch_port_setup_targets()
20ae97ad3349 cxl: Add interleave encoding validity helpers