[PATCH v7 net 0/4] Fix broken link on Xilinx's AXI Ethernet in SGMII mode

[PATCH v7 net 0/4] Fix broken link on Xilinx's AXI Ethernet in SGMII mode

[Andy Chiu]

The Ethernet driver use phy-handle to reference the PCS/PMA PHY. This
could be a problem if one wants to configure an external PHY via phylink,
since it use the same phandle to get the PHY. To fix this, introduce a
dedicated pcs-handle to point to the PCS/PMA PHY and deprecate the use
of pointing it with phy-handle. A similar use case of pcs-handle can be
seen on dpaa2 as well.

--- patch v5 ---
 - Re-apply the v4 patch on the net tree.
 - Describe the pcs-handle DT binding at ethernet-controller level.
--- patch v6 ---
 - Remove "preferrably" to clearify usage of pcs_handle.
--- patch v7 ---
 - Rebase the patch on latest net/master

Andy Chiu (4):
  net: axienet: setup mdio unconditionally
  net: axienet: factor out phy_node in struct axienet_local
  dt-bindings: net: add pcs-handle attribute
  net: axiemac: use a phandle to reference pcs_phy

 .../bindings/net/ethernet-controller.yaml     |  6 ++++
 .../bindings/net/xilinx_axienet.txt           |  8 ++++-
 drivers/net/ethernet/xilinx/xilinx_axienet.h  |  2 --
 .../net/ethernet/xilinx/xilinx_axienet_main.c | 33 ++++++++++---------
 4 files changed, 31 insertions(+), 18 deletions(-)

-- 
2.34.1

[PATCH v7 net 1/4] net: axienet: setup mdio unconditionally

[Andy Chiu]

The call to axienet_mdio_setup should not depend on whether "phy-node"
pressents on the DT. Besides, since `lp->phy_node` is used if PHY is in
SGMII or 100Base-X modes, move it into the if statement. And the next patch
will remove `lp->phy_node` from driver's private structure and do an
of_node_put on it right away after use since it is not used elsewhere.

Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
Reviewed-by: Robert Hancock <robert.hancock@calian.com>
---
 drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index c7eb05e4a6bf..78a991bbbcf9 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -2064,15 +2064,14 @@ static int axienet_probe(struct platform_device *pdev)
 	if (ret)
 		goto cleanup_clk;
 
-	lp->phy_node = of_parse_phandle(pdev->dev.of_node, "phy-handle", 0);
-	if (lp->phy_node) {
-		ret = axienet_mdio_setup(lp);
-		if (ret)
-			dev_warn(&pdev->dev,
-				 "error registering MDIO bus: %d\n", ret);
-	}
+	ret = axienet_mdio_setup(lp);
+	if (ret)
+		dev_warn(&pdev->dev,
+			 "error registering MDIO bus: %d\n", ret);
+
 	if (lp->phy_mode == PHY_INTERFACE_MODE_SGMII ||
 	    lp->phy_mode == PHY_INTERFACE_MODE_1000BASEX) {
+		lp->phy_node = of_parse_phandle(pdev->dev.of_node, "phy-handle", 0);
 		if (!lp->phy_node) {
 			dev_err(&pdev->dev, "phy-handle required for 1000BaseX/SGMII\n");
 			ret = -EINVAL;
-- 
2.34.1

[PATCH v7 net 2/4] net: axienet: factor out phy_node in struct axienet_local

[Andy Chiu]

the struct member `phy_node` of struct axienet_local is not used by the
driver anymore after initialization. It might be a remnent of old code
and could be removed.

Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
Reviewed-by: Robert Hancock <robert.hancock@calian.com>
---
 drivers/net/ethernet/xilinx/xilinx_axienet.h      |  2 --
 drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 13 +++++--------
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet.h b/drivers/net/ethernet/xilinx/xilinx_axienet.h
index 0f9c88dd1a4a..d5c1e5c4a508 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet.h
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet.h
@@ -433,8 +433,6 @@ struct axienet_local {
 	struct net_device *ndev;
 	struct device *dev;
 
-	struct device_node *phy_node;
-
 	struct phylink *phylink;
 	struct phylink_config phylink_config;
 
diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index 78a991bbbcf9..3daef64a85bd 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -2071,17 +2071,19 @@ static int axienet_probe(struct platform_device *pdev)
 
 	if (lp->phy_mode == PHY_INTERFACE_MODE_SGMII ||
 	    lp->phy_mode == PHY_INTERFACE_MODE_1000BASEX) {
-		lp->phy_node = of_parse_phandle(pdev->dev.of_node, "phy-handle", 0);
-		if (!lp->phy_node) {
+		np = of_parse_phandle(pdev->dev.of_node, "phy-handle", 0);
+		if (!np) {
 			dev_err(&pdev->dev, "phy-handle required for 1000BaseX/SGMII\n");
 			ret = -EINVAL;
 			goto cleanup_mdio;
 		}
-		lp->pcs_phy = of_mdio_find_device(lp->phy_node);
+		lp->pcs_phy = of_mdio_find_device(np);
 		if (!lp->pcs_phy) {
 			ret = -EPROBE_DEFER;
+			of_node_put(np);
 			goto cleanup_mdio;
 		}
+		of_node_put(np);
 		lp->pcs.ops = &axienet_pcs_ops;
 		lp->pcs.poll = true;
 	}
@@ -2124,8 +2126,6 @@ static int axienet_probe(struct platform_device *pdev)
 		put_device(&lp->pcs_phy->dev);
 	if (lp->mii_bus)
 		axienet_mdio_teardown(lp);
-	of_node_put(lp->phy_node);
-
 cleanup_clk:
 	clk_bulk_disable_unprepare(XAE_NUM_MISC_CLOCKS, lp->misc_clks);
 	clk_disable_unprepare(lp->axi_clk);
@@ -2154,9 +2154,6 @@ static int axienet_remove(struct platform_device *pdev)
 	clk_bulk_disable_unprepare(XAE_NUM_MISC_CLOCKS, lp->misc_clks);
 	clk_disable_unprepare(lp->axi_clk);
 
-	of_node_put(lp->phy_node);
-	lp->phy_node = NULL;
-
 	free_netdev(ndev);
 
 	return 0;
-- 
2.34.1

[PATCH v7 net 3/4] dt-bindings: net: add pcs-handle attribute

[Andy Chiu]

Document the new pcs-handle attribute to support connecting to an
external PHY. For Xilinx's AXI Ethernet, this is used when the core
operates in SGMII or 1000Base-X modes and links through the internal
PCS/PMA PHY.

Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
---
 .../devicetree/bindings/net/ethernet-controller.yaml      | 6 ++++++
 Documentation/devicetree/bindings/net/xilinx_axienet.txt  | 8 +++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/net/ethernet-controller.yaml b/Documentation/devicetree/bindings/net/ethernet-controller.yaml
index 817794e56227..4f15463611f8 100644
--- a/Documentation/devicetree/bindings/net/ethernet-controller.yaml
+++ b/Documentation/devicetree/bindings/net/ethernet-controller.yaml
@@ -106,6 +106,12 @@ properties:
   phy-mode:
     $ref: "#/properties/phy-connection-type"
 
+  pcs-handle:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      Specifies a reference to a node representing a PCS PHY device on a MDIO
+      bus to link with an external PHY (phy-handle) if exists.
+
   phy-handle:
     $ref: /schemas/types.yaml#/definitions/phandle
     description:
diff --git a/Documentation/devicetree/bindings/net/xilinx_axienet.txt b/Documentation/devicetree/bindings/net/xilinx_axienet.txt
index b8e4894bc634..1aa4c6006cd0 100644
--- a/Documentation/devicetree/bindings/net/xilinx_axienet.txt
+++ b/Documentation/devicetree/bindings/net/xilinx_axienet.txt
@@ -26,7 +26,8 @@ Required properties:
 		  specified, the TX/RX DMA interrupts should be on that node
 		  instead, and only the Ethernet core interrupt is optionally
 		  specified here.
-- phy-handle	: Should point to the external phy device.
+- phy-handle	: Should point to the external phy device if exists. Pointing
+		  this to the PCS/PMA PHY is deprecated and should be avoided.
 		  See ethernet.txt file in the same directory.
 - xlnx,rxmem	: Set to allocated memory buffer for Rx/Tx in the hardware
 
@@ -68,6 +69,11 @@ Optional properties:
 		  required through the core's MDIO interface (i.e. always,
 		  unless the PHY is accessed through a different bus).
 
+ - pcs-handle: 	  Phandle to the internal PCS/PMA PHY in SGMII or 1000Base-X
+		  modes, where "pcs-handle" should be used to point
+		  to the PCS/PMA PHY, and "phy-handle" should point to an
+		  external PHY if exists.
+
 Example:
 	axi_ethernet_eth: ethernet@40c00000 {
 		compatible = "xlnx,axi-ethernet-1.00.a";
-- 
2.34.1

Re: [PATCH v7 net 3/4] dt-bindings: net: add pcs-handle attribute

[Rob Herring]

On Tue, 29 Mar 2022 10:49:20 +0800, Andy Chiu wrote:
> Document the new pcs-handle attribute to support connecting to an
> external PHY. For Xilinx's AXI Ethernet, this is used when the core
> operates in SGMII or 1000Base-X modes and links through the internal
> PCS/PMA PHY.
> 
> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
> Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
> ---
>  .../devicetree/bindings/net/ethernet-controller.yaml      | 6 ++++++
>  Documentation/devicetree/bindings/net/xilinx_axienet.txt  | 8 +++++++-
>  2 files changed, 13 insertions(+), 1 deletion(-)
> 

Reviewed-by: Rob Herring <robh@kernel.org>

[PATCH v7 net 4/4] net: axiemac: use a phandle to reference pcs_phy

[Andy Chiu]

In some SGMII use cases where both a fixed link external PHY and the
internal PCS/PMA PHY need to be configured, we should explicitly use a
phandle "pcs-phy" to get the reference to the PCS/PMA PHY. Otherwise, the
driver would use "phy-handle" in the DT as the reference to both the
external and the internal PCS/PMA PHY.

In other cases where the core is connected to a SFP cage, we could still
point phy-handle to the intenal PCS/PMA PHY, and let the driver connect
to the SFP module, if exist, via phylink.

Fixes: 1a02556086fc (net: axienet: Properly handle PCS/PMA PHY for 1000BaseX mode)
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
Reviewed-by: Robert Hancock <robert.hancock@calian.com>
---
 drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index 3daef64a85bd..d6fc3f7acdf0 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -2071,9 +2071,16 @@ static int axienet_probe(struct platform_device *pdev)
 
 	if (lp->phy_mode == PHY_INTERFACE_MODE_SGMII ||
 	    lp->phy_mode == PHY_INTERFACE_MODE_1000BASEX) {
-		np = of_parse_phandle(pdev->dev.of_node, "phy-handle", 0);
+		np = of_parse_phandle(pdev->dev.of_node, "pcs-handle", 0);
 		if (!np) {
-			dev_err(&pdev->dev, "phy-handle required for 1000BaseX/SGMII\n");
+			/* Deprecated: Always use "pcs-handle" for pcs_phy.
+			 * Falling back to "phy-handle" here is only for
+			 * backward compatibility with old device trees.
+			 */
+			np = of_parse_phandle(pdev->dev.of_node, "phy-handle", 0);
+		}
+		if (!np) {
+			dev_err(&pdev->dev, "pcs-handle (preferred) or phy-handle required for 1000BaseX/SGMII\n");
 			ret = -EINVAL;
 			goto cleanup_mdio;
 		}
-- 
2.34.1

Re: [PATCH v7 net 4/4] net: axiemac: use a phandle to reference pcs_phy

[Jakub Kicinski]

On Tue, 29 Mar 2022 10:49:21 +0800 Andy Chiu wrote:
> In some SGMII use cases where both a fixed link external PHY and the
> internal PCS/PMA PHY need to be configured, we should explicitly use a
> phandle "pcs-phy" to get the reference to the PCS/PMA PHY. Otherwise, the
> driver would use "phy-handle" in the DT as the reference to both the
> external and the internal PCS/PMA PHY.
> 
> In other cases where the core is connected to a SFP cage, we could still
> point phy-handle to the intenal PCS/PMA PHY, and let the driver connect
> to the SFP module, if exist, via phylink.
> 
> Fixes: 1a02556086fc (net: axienet: Properly handle PCS/PMA PHY for 1000BaseX mode)
> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
> Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
> Reviewed-by: Robert Hancock <robert.hancock@calian.com>

I'm not sure if this is a fix or adding support for a new configuration.
Andrew, WDYT?

If it really is a fix and needs to be backported we should take patch 2
out of this series, and post it separately later. Refactoring does not
belong in stable trees.

Re: [PATCH v7 net 4/4] net: axiemac: use a phandle to reference pcs_phy

[Andrew Lunn]

On Tue, Mar 29, 2022 at 03:56:09PM -0700, Jakub Kicinski wrote:
> On Tue, 29 Mar 2022 10:49:21 +0800 Andy Chiu wrote:
> > In some SGMII use cases where both a fixed link external PHY and the
> > internal PCS/PMA PHY need to be configured, we should explicitly use a
> > phandle "pcs-phy" to get the reference to the PCS/PMA PHY. Otherwise, the
> > driver would use "phy-handle" in the DT as the reference to both the
> > external and the internal PCS/PMA PHY.
> > 
> > In other cases where the core is connected to a SFP cage, we could still
> > point phy-handle to the intenal PCS/PMA PHY, and let the driver connect
> > to the SFP module, if exist, via phylink.
> > 
> > Fixes: 1a02556086fc (net: axienet: Properly handle PCS/PMA PHY for 1000BaseX mode)
> > Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
> > Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
> > Reviewed-by: Robert Hancock <robert.hancock@calian.com>
> 
> I'm not sure if this is a fix or adding support for a new configuration.
> Andrew, WDYT?

I guess it fails this stable rule:

It must fix a problem that causes a build error (but not for things
marked CONFIG_BROKEN), an oops, a hang, data corruption, a real
security issue, or some “oh, that’s not good” issue. In short,
something critical.

So this probably should be for net-next.

   Andrew

Re: [PATCH v7 net 4/4] net: axiemac: use a phandle to reference pcs_phy

[Jakub Kicinski]

On Wed, 30 Mar 2022 03:25:15 +0200 Andrew Lunn wrote:
> > I'm not sure if this is a fix or adding support for a new configuration.
> > Andrew, WDYT?  
> 
> I guess it fails this stable rule:
> 
> It must fix a problem that causes a build error (but not for things
> marked CONFIG_BROKEN), an oops, a hang, data corruption, a real
> security issue, or some “oh, that’s not good” issue. In short,
> something critical.
> 
> So this probably should be for net-next.

Okay, thanks! Just to spell it out this means you'll need to hold off
with reposting, Andy, until net-next re-opens (which means until
5.18-rc1 kernel version is tagged by Linus, see the netdev-FAQ).

You should also drop the Fixes tag from patch 4. The change will make
it to Linux 5.19 and won't be backported to stable.

Re: [PATCH v7 net 4/4] net: axiemac: use a phandle to reference pcs_phy

[Andy Chiu]

thanks for explaining this,

I will make the change accordingly and post it to net-next when available.

Andy