[PATCH phy-next 1/5] dt-bindings: phy: lynx-28g: add compatible strings per SerDes and instantiation

[PATCH phy-next 1/5] dt-bindings: phy: lynx-28g: add compatible strings per SerDes and instantiation

[Vladimir Oltean]

The 28G Lynx SerDes is instantiated 3 times in the NXP LX2160A SoC and
twice in the NXP LX2162A. All these instances share the same register
map, but the number of lanes and the protocols supported by each lane
differs in a way that isn't detectable by the programming model.

For example, not all lanes of all SerDes block instantiations support
25GbE.

So, using a generic "fsl,lynx-28g" compatible string and expecting all
SerDes instantiations to use it was a mistake that needs to be fixed.

The option chosen is to encode the SoC and the SerDes instance in the
compatible string, with everything else being the responsibility of the
driver to derive.

An alternative considered but dismissed was to add sufficient device
tree properties to describe the per-lane differences (implying:
supported protocols), as well as the different lane count.

Any decision made for the 28G Lynx should be consistent with the
decisions taken for the yet-to-be-introduced 10G Lynx SerDes (older
generation for older SoCs), because of how similar they are.

I've seen the alternative at play in this unmerged patch set for the 10G
Lynx here, and I didn't like it:
https://lore.kernel.org/linux-phy/20230413160607.4128315-3-sean.anderson@seco.com/

This is because there, we have a higher degree of variability in the
PCCR register values that need to be written per protocol. This makes
that approach more drawn-out and more prone to errors, compared to the
compatible strings which are more succinct and obviously correct.

NXP SoC reference manuals clearly document the SerDes instantiations as
not identical, and refers to them as such (SerDes 1, 2, etc).

The per-SoC compatible string is prepended to the "fsl,lynx-28g" generic
compatible, which is left there for compatibility with old kernels. An
exception would be LX2160A SerDes #3, which at the time of writing is
not described in fsl-lx2160a.dtsi. As "fsl,lx2160a-serdes3" implies it
is a 28G Lynx SerDes, it makes "fsl,lynx-28g" redundant so we don't
accept it.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
---
Cc: Rob Herring <robh@kernel.org>
Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: devicetree@vger.kernel.org

Previously submitted here:
https://lore.kernel.org/linux-phy/20260114152111.625350-3-vladimir.oltean@nxp.com/

Changes:
- Update commit message to remove leftover information stating that we
  use the per-SoC compatible strings to impose constraints
- Add review tag from Rob Herring
---
 .../devicetree/bindings/phy/fsl,lynx-28g.yaml | 33 +++++++++++++++++--
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/phy/fsl,lynx-28g.yaml b/Documentation/devicetree/bindings/phy/fsl,lynx-28g.yaml
index e96229c2f8fb..8375bca810cc 100644
--- a/Documentation/devicetree/bindings/phy/fsl,lynx-28g.yaml
+++ b/Documentation/devicetree/bindings/phy/fsl,lynx-28g.yaml
@@ -9,10 +9,37 @@ title: Freescale Lynx 28G SerDes PHY
 maintainers:
   - Ioana Ciornei <ioana.ciornei@nxp.com>
 
+description:
+  The Lynx 28G is a multi-lane, multi-protocol SerDes (PCIe, SATA, Ethernet)
+  present in multiple instances on NXP LX2160A and LX2162A SoCs. All instances
+  share a common register map and programming model, however they differ in
+  supported protocols per lane in a way that is not detectable by said
+  programming model without prior knowledge. The distinction is made through
+  the compatible string.
+
 properties:
   compatible:
-    enum:
-      - fsl,lynx-28g
+    oneOf:
+      - const: fsl,lynx-28g
+        deprecated: true
+        description:
+          Legacy compatibility string for Lynx 28G SerDes. Any assumption
+          regarding whether a certain lane supports a certain protocol may
+          be incorrect. Deprecated except when used as a fallback. Use
+          device-specific strings instead.
+      - items:
+          - const: fsl,lx2160a-serdes1
+          - const: fsl,lynx-28g
+      - items:
+          - const: fsl,lx2160a-serdes2
+          - const: fsl,lynx-28g
+      - items:
+          - const: fsl,lx2162a-serdes1
+          - const: fsl,lynx-28g
+      - items:
+          - const: fsl,lx2162a-serdes2
+          - const: fsl,lynx-28g
+      - const: fsl,lx2160a-serdes3
 
   reg:
     maxItems: 1
@@ -60,7 +87,7 @@ examples:
       #size-cells = <2>;
 
       serdes@1ea0000 {
-        compatible = "fsl,lynx-28g";
+        compatible = "fsl,lx2160a-serdes1", "fsl,lynx-28g";
         reg = <0x0 0x1ea0000 0x0 0x1e30>;
         #address-cells = <1>;
         #size-cells = <0>;
-- 
2.34.1

[PATCH phy-next 2/5] dt-bindings: phy: lynx-28g: add constraint on LX2162A lane indices

[Vladimir Oltean]

The SerDes 1 of LX2162A has fewer lanes than all other instances, and
strangely, their indices are not 0-3, but 4-7.

This is a best-effort constraint, since we can only impose it when using
per-SoC compatible string and per-lane OF nodes.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
Cc: Rob Herring <robh@kernel.org>
Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: devicetree@vger.kernel.org

Patch previously submitted at:
https://lore.kernel.org/linux-phy/20260114152111.625350-4-vladimir.oltean@nxp.com/

Changes:
- remove redundant patternProperties: "^phy@[0-7]$": true from the
  match; having it makes no difference
- clarify that the constraint is best effort
---
 .../devicetree/bindings/phy/fsl,lynx-28g.yaml     | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/Documentation/devicetree/bindings/phy/fsl,lynx-28g.yaml b/Documentation/devicetree/bindings/phy/fsl,lynx-28g.yaml
index 8375bca810cc..d73591315d4b 100644
--- a/Documentation/devicetree/bindings/phy/fsl,lynx-28g.yaml
+++ b/Documentation/devicetree/bindings/phy/fsl,lynx-28g.yaml
@@ -78,6 +78,21 @@ required:
   - reg
   - "#phy-cells"
 
+allOf:
+  # LX2162A SerDes 1 has fewer lanes than the others
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: fsl,lx2162a-serdes1
+    then:
+      patternProperties:
+        "^phy@[0-7]$":
+          properties:
+            reg:
+              minimum: 4
+              maximum: 7
+
 additionalProperties: false
 
 examples:
-- 
2.34.1

[PATCH phy-next 4/5] phy: lynx-28g: probe on per-SoC and per-instance compatible strings

[Vladimir Oltean]

Add driver support for probing on the new, per-instance and per-SoC
bindings, which provide the main benefit that they allow rejecting
unsupported protocols per lane (10GbE on SerDes 2 lanes 0-5), but they
also allow avoiding the creation of PHYs for lanes that don't exist
(LX2162A lanes 0-3).

For old device trees with just "fsl,lynx-28g", the only things that
change are:

- a probe time warning/encouragement to update the device tree. This is
  warranted by the fact that using "fsl,lynx-28g" may already provide
  incorrect behaviour (undetected absent 10GbE support on LX2160A
  SerDes 2 lanes 0-5). But we retain bug compatibility nonetheless.

- the feature set is frozen in time (e.g. no 25GbE). Since we cannot
  guarantee that this protocol will work on a lane, just err on the safe
  side and don't offer it (and require a device tree update to get it).

In terms of code, the lynx_28g_supports_lane_mode() function prototype
changes. It was a SerDes-global function and now becomes per lane, to
reflect the specific capabilities each instance may have. The
implementation goes through priv->info->lane_supports_mode().

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
Cc: Rob Herring <robh@kernel.org>
Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: devicetree@vger.kernel.org

Change previously submitted at:
https://lore.kernel.org/linux-phy/20260114152111.625350-5-vladimir.oltean@nxp.com/

Changes:
- reword commit message
---
 drivers/phy/freescale/phy-fsl-lynx-28g.c | 126 +++++++++++++++++++++--
 1 file changed, 116 insertions(+), 10 deletions(-)

diff --git a/drivers/phy/freescale/phy-fsl-lynx-28g.c b/drivers/phy/freescale/phy-fsl-lynx-28g.c
index 6d0c395d20e5..5eddc2723e78 100644
--- a/drivers/phy/freescale/phy-fsl-lynx-28g.c
+++ b/drivers/phy/freescale/phy-fsl-lynx-28g.c
@@ -446,9 +446,15 @@ struct lynx_28g_lane {
 	enum lynx_lane_mode mode;
 };
 
+struct lynx_info {
+	bool (*lane_supports_mode)(int lane, enum lynx_lane_mode mode);
+	int first_lane;
+};
+
 struct lynx_28g_priv {
 	void __iomem *base;
 	struct device *dev;
+	const struct lynx_info *info;
 	/* Serialize concurrent access to registers shared between lanes,
 	 * like PCCn
 	 */
@@ -513,11 +519,18 @@ static enum lynx_lane_mode phy_interface_to_lane_mode(phy_interface_t intf)
 	}
 }
 
-static bool lynx_28g_supports_lane_mode(struct lynx_28g_priv *priv,
+/* A lane mode is supported if we have a PLL that can provide its required
+ * clock net, and if there is a protocol converter for that mode on that lane.
+ */
+static bool lynx_28g_supports_lane_mode(struct lynx_28g_lane *lane,
 					enum lynx_lane_mode mode)
 {
+	struct lynx_28g_priv *priv = lane->priv;
 	int i;
 
+	if (!priv->info->lane_supports_mode(lane->id, mode))
+		return false;
+
 	for (i = 0; i < LYNX_28G_NUM_PLL; i++) {
 		if (PLLnRSTCTL_DIS(priv->pll[i].rstctl))
 			continue;
@@ -783,6 +796,87 @@ static int lynx_28g_get_pcvt_offset(int lane, enum lynx_lane_mode lane_mode)
 	}
 }
 
+static bool lx2160a_serdes1_lane_supports_mode(int lane,
+					       enum lynx_lane_mode mode)
+{
+	return true;
+}
+
+static bool lx2160a_serdes2_lane_supports_mode(int lane,
+					       enum lynx_lane_mode mode)
+{
+	switch (mode) {
+	case LANE_MODE_1000BASEX_SGMII:
+		return true;
+	case LANE_MODE_USXGMII:
+	case LANE_MODE_10GBASER:
+		return lane == 6 || lane == 7;
+	default:
+		return false;
+	}
+}
+
+static bool lx2160a_serdes3_lane_supports_mode(int lane,
+					       enum lynx_lane_mode mode)
+{
+	/*
+	 * Non-networking SerDes, and this driver supports only
+	 * networking protocols
+	 */
+	return false;
+}
+
+static bool lx2162a_serdes1_lane_supports_mode(int lane,
+					       enum lynx_lane_mode mode)
+{
+	return true;
+}
+
+static bool lx2162a_serdes2_lane_supports_mode(int lane,
+					       enum lynx_lane_mode mode)
+{
+	return lx2160a_serdes2_lane_supports_mode(lane, mode);
+}
+
+/* Feature set is not expected to grow for the deprecated compatible string */
+static bool lynx_28g_compat_lane_supports_mode(int lane,
+					       enum lynx_lane_mode mode)
+{
+	switch (mode) {
+	case LANE_MODE_1000BASEX_SGMII:
+	case LANE_MODE_USXGMII:
+	case LANE_MODE_10GBASER:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct lynx_info lynx_info_compat = {
+	.lane_supports_mode = lynx_28g_compat_lane_supports_mode,
+};
+
+static const struct lynx_info lynx_info_lx2160a_serdes1 = {
+	.lane_supports_mode = lx2160a_serdes1_lane_supports_mode,
+};
+
+static const struct lynx_info lynx_info_lx2160a_serdes2 = {
+	.lane_supports_mode = lx2160a_serdes2_lane_supports_mode,
+};
+
+static const struct lynx_info lynx_info_lx2160a_serdes3 = {
+	.lane_supports_mode = lx2160a_serdes3_lane_supports_mode,
+};
+
+static const struct lynx_info lynx_info_lx2162a_serdes1 = {
+	.lane_supports_mode = lx2162a_serdes1_lane_supports_mode,
+	.first_lane = 4,
+};
+
+static const struct lynx_info lynx_info_lx2162a_serdes2 = {
+	.lane_supports_mode = lx2162a_serdes2_lane_supports_mode,
+};
+
 static int lynx_pccr_read(struct lynx_28g_lane *lane, enum lynx_lane_mode mode,
 			  u32 *val)
 {
@@ -1035,7 +1129,6 @@ static int lynx_28g_lane_enable_pcvt(struct lynx_28g_lane *lane,
 static int lynx_28g_set_mode(struct phy *phy, enum phy_mode mode, int submode)
 {
 	struct lynx_28g_lane *lane = phy_get_drvdata(phy);
-	struct lynx_28g_priv *priv = lane->priv;
 	int powered_up = lane->powered_up;
 	enum lynx_lane_mode lane_mode;
 	int err = 0;
@@ -1047,7 +1140,7 @@ static int lynx_28g_set_mode(struct phy *phy, enum phy_mode mode, int submode)
 		return -EOPNOTSUPP;
 
 	lane_mode = phy_interface_to_lane_mode(submode);
-	if (!lynx_28g_supports_lane_mode(priv, lane_mode))
+	if (!lynx_28g_supports_lane_mode(lane, lane_mode))
 		return -EOPNOTSUPP;
 
 	if (lane_mode == lane->mode)
@@ -1083,14 +1176,13 @@ static int lynx_28g_validate(struct phy *phy, enum phy_mode mode, int submode,
 			     union phy_configure_opts *opts __always_unused)
 {
 	struct lynx_28g_lane *lane = phy_get_drvdata(phy);
-	struct lynx_28g_priv *priv = lane->priv;
 	enum lynx_lane_mode lane_mode;
 
 	if (mode != PHY_MODE_ETHERNET)
 		return -EOPNOTSUPP;
 
 	lane_mode = phy_interface_to_lane_mode(submode);
-	if (!lynx_28g_supports_lane_mode(priv, lane_mode))
+	if (!lynx_28g_supports_lane_mode(lane, lane_mode))
 		return -EOPNOTSUPP;
 
 	return 0;
@@ -1183,7 +1275,7 @@ static void lynx_28g_cdr_lock_check(struct work_struct *work)
 	u32 rrstctl;
 	int err, i;
 
-	for (i = 0; i < LYNX_28G_NUM_LANE; i++) {
+	for (i = priv->info->first_lane; i < LYNX_28G_NUM_LANE; i++) {
 		lane = &priv->lane[i];
 		if (!lane->phy)
 			continue;
@@ -1253,7 +1345,8 @@ static struct phy *lynx_28g_xlate(struct device *dev,
 
 	idx = args->args[0];
 
-	if (WARN_ON(idx >= LYNX_28G_NUM_LANE))
+	if (WARN_ON(idx >= LYNX_28G_NUM_LANE ||
+		    idx < priv->info->first_lane))
 		return ERR_PTR(-EINVAL);
 
 	return priv->lane[idx].phy;
@@ -1297,10 +1390,18 @@ static int lynx_28g_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	priv->dev = dev;
+	priv->info = of_device_get_match_data(dev);
 	dev_set_drvdata(dev, priv);
 	spin_lock_init(&priv->pcc_lock);
 	INIT_DELAYED_WORK(&priv->cdr_check, lynx_28g_cdr_lock_check);
 
+	/*
+	 * If we get here it means we probed on a device tree where
+	 * "fsl,lynx-28g" wasn't the fallback, but the sole compatible string.
+	 */
+	if (priv->info == &lynx_info_compat)
+		dev_warn(dev, "Please update device tree to use per-device compatible strings\n");
+
 	priv->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(priv->base))
 		return PTR_ERR(priv->base);
@@ -1323,7 +1424,7 @@ static int lynx_28g_probe(struct platform_device *pdev)
 				return -EINVAL;
 			}
 
-			if (reg >= LYNX_28G_NUM_LANE) {
+			if (reg < priv->info->first_lane || reg >= LYNX_28G_NUM_LANE) {
 				dev_err(dev, "\"reg\" property out of range for %pOF\n", child);
 				of_node_put(child);
 				return -EINVAL;
@@ -1336,7 +1437,7 @@ static int lynx_28g_probe(struct platform_device *pdev)
 			}
 		}
 	} else {
-		for (int i = 0; i < LYNX_28G_NUM_LANE; i++) {
+		for (int i = priv->info->first_lane; i < LYNX_28G_NUM_LANE; i++) {
 			err = lynx_28g_probe_lane(priv, i, NULL);
 			if (err)
 				return err;
@@ -1362,7 +1463,12 @@ static void lynx_28g_remove(struct platform_device *pdev)
 }
 
 static const struct of_device_id lynx_28g_of_match_table[] = {
-	{ .compatible = "fsl,lynx-28g" },
+	{ .compatible = "fsl,lx2160a-serdes1", .data = &lynx_info_lx2160a_serdes1 },
+	{ .compatible = "fsl,lx2160a-serdes2", .data = &lynx_info_lx2160a_serdes2 },
+	{ .compatible = "fsl,lx2160a-serdes3", .data = &lynx_info_lx2160a_serdes3 },
+	{ .compatible = "fsl,lx2162a-serdes1", .data = &lynx_info_lx2162a_serdes1 },
+	{ .compatible = "fsl,lx2162a-serdes2", .data = &lynx_info_lx2162a_serdes2 },
+	{ .compatible = "fsl,lynx-28g", .data = &lynx_info_compat }, /* fallback, keep last */
 	{ },
 };
 MODULE_DEVICE_TABLE(of, lynx_28g_of_match_table);
-- 
2.34.1

Re: [PATCH phy-next 2/5] dt-bindings: phy: lynx-28g: add constraint on LX2162A lane indices

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 440 bytes --]

On Mon, May 11, 2026 at 06:00:20PM +0300, Vladimir Oltean wrote:
> The SerDes 1 of LX2162A has fewer lanes than all other instances, and
> strangely, their indices are not 0-3, but 4-7.
> 
> This is a best-effort constraint, since we can only impose it when using
> per-SoC compatible string and per-lane OF nodes.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Acked-by: Conor Dooley <conor.dooley@microchip.com>

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

Re: [PATCH phy-next 4/5] phy: lynx-28g: probe on per-SoC and per-instance compatible strings

[Ioana Ciornei]

On Mon, May 11, 2026 at 06:00:22PM +0300, Vladimir Oltean wrote:
> Add driver support for probing on the new, per-instance and per-SoC
> bindings, which provide the main benefit that they allow rejecting
> unsupported protocols per lane (10GbE on SerDes 2 lanes 0-5), but they
> also allow avoiding the creation of PHYs for lanes that don't exist
> (LX2162A lanes 0-3).
> 
> For old device trees with just "fsl,lynx-28g", the only things that
> change are:
> 
> - a probe time warning/encouragement to update the device tree. This is
>   warranted by the fact that using "fsl,lynx-28g" may already provide
>   incorrect behaviour (undetected absent 10GbE support on LX2160A
>   SerDes 2 lanes 0-5). But we retain bug compatibility nonetheless.
> 
> - the feature set is frozen in time (e.g. no 25GbE). Since we cannot
>   guarantee that this protocol will work on a lane, just err on the safe
>   side and don't offer it (and require a device tree update to get it).
> 
> In terms of code, the lynx_28g_supports_lane_mode() function prototype
> changes. It was a SerDes-global function and now becomes per lane, to
> reflect the specific capabilities each instance may have. The
> implementation goes through priv->info->lane_supports_mode().
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>