[PATCH net v3 0/3] Clean up and fix error handling in mdio_mux_init()

[PATCH net v3 0/3] Clean up and fix error handling in mdio_mux_init()

[Saravana Kannan]

This patch series was started due to -EPROBE_DEFER not being handled
correctly in mdio_mux_init() and causing issues [1]. While at it, I also
did some more error handling fixes and clean ups. The -EPROBE_DEFER fix is
the last patch.

Ideally, in the last patch we'd treat any error similar to -EPROBE_DEFER
but I'm not sure if it'll break any board/platforms where some child
mdiobus never successfully registers. If we treated all errors similar to
-EPROBE_DEFER, then none of the child mdiobus will work and that might be a
regression. If people are sure this is not a real case, then I can fix up
the last patch to always fail the entire mdio-mux init if any of the child
mdiobus registration fails.

Cc: Marc Zyngier <maz@kernel.org>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Kevin Hilman <khilman@baylibre.com>
[1] - https://lore.kernel.org/lkml/CAGETcx95kHrv8wA-O+-JtfH7H9biJEGJtijuPVN0V5dUKUAB3A@mail.gmail.com/#t

v1 -> v2:
- Added Acked-by, Tested-by and Reviewed-by
- Fixing the subject so it goes to "net" tree
v2 -> v3:
- Added Fixes tag to all the patches

Saravana Kannan (3):
  net: mdio-mux: Delete unnecessary devm_kfree
  net: mdio-mux: Don't ignore memory allocation errors
  net: mdio-mux: Handle -EPROBE_DEFER correctly

 drivers/net/mdio/mdio-mux.c | 37 ++++++++++++++++++++++++-------------
 1 file changed, 24 insertions(+), 13 deletions(-)

-- 
2.33.0.rc1.237.g0d66db33f3-goog

[PATCH net v3 1/3] net: mdio-mux: Delete unnecessary devm_kfree

[Saravana Kannan]

The whole point of devm_* APIs is that you don't have to undo them if you
are returning an error that's going to get propagated out of a probe()
function. So delete unnecessary devm_kfree() call in the error return path.

Fixes: b60161668199 ("mdio: mux: Correct mdio_mux_init error path issues")
Signed-off-by: Saravana Kannan <saravanak@google.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Marc Zyngier <maz@kernel.org>
Tested-by: Marc Zyngier <maz@kernel.org>
Acked-by: Kevin Hilman <khilman@baylibre.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
---
 drivers/net/mdio/mdio-mux.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/mdio/mdio-mux.c b/drivers/net/mdio/mdio-mux.c
index 110e4ee85785..5b37284f54d6 100644
--- a/drivers/net/mdio/mdio-mux.c
+++ b/drivers/net/mdio/mdio-mux.c
@@ -181,7 +181,6 @@ int mdio_mux_init(struct device *dev,
 	}
 
 	dev_err(dev, "Error: No acceptable child buses found\n");
-	devm_kfree(dev, pb);
 err_pb_kz:
 	put_device(&parent_bus->dev);
 err_parent_bus:
-- 
2.33.0.rc1.237.g0d66db33f3-goog

[PATCH net v3 2/3] net: mdio-mux: Don't ignore memory allocation errors

[Saravana Kannan]

If we are seeing memory allocation errors, don't try to continue
registering child mdiobus devices. It's unlikely they'll succeed.

Fixes: 342fa1964439 ("mdio: mux: make child bus walking more permissive and errors more verbose")
Signed-off-by: Saravana Kannan <saravanak@google.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Marc Zyngier <maz@kernel.org>
Tested-by: Marc Zyngier <maz@kernel.org>
Acked-by: Kevin Hilman <khilman@baylibre.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
---
 drivers/net/mdio/mdio-mux.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/drivers/net/mdio/mdio-mux.c b/drivers/net/mdio/mdio-mux.c
index 5b37284f54d6..13035e2685c4 100644
--- a/drivers/net/mdio/mdio-mux.c
+++ b/drivers/net/mdio/mdio-mux.c
@@ -82,6 +82,17 @@ static int mdio_mux_write(struct mii_bus *bus, int phy_id,
 
 static int parent_count;
 
+static void mdio_mux_uninit_children(struct mdio_mux_parent_bus *pb)
+{
+	struct mdio_mux_child_bus *cb = pb->children;
+
+	while (cb) {
+		mdiobus_unregister(cb->mii_bus);
+		mdiobus_free(cb->mii_bus);
+		cb = cb->next;
+	}
+}
+
 int mdio_mux_init(struct device *dev,
 		  struct device_node *mux_node,
 		  int (*switch_fn)(int cur, int desired, void *data),
@@ -144,7 +155,7 @@ int mdio_mux_init(struct device *dev,
 		cb = devm_kzalloc(dev, sizeof(*cb), GFP_KERNEL);
 		if (!cb) {
 			ret_val = -ENOMEM;
-			continue;
+			goto err_loop;
 		}
 		cb->bus_number = v;
 		cb->parent = pb;
@@ -152,8 +163,7 @@ int mdio_mux_init(struct device *dev,
 		cb->mii_bus = mdiobus_alloc();
 		if (!cb->mii_bus) {
 			ret_val = -ENOMEM;
-			devm_kfree(dev, cb);
-			continue;
+			goto err_loop;
 		}
 		cb->mii_bus->priv = cb;
 
@@ -181,6 +191,10 @@ int mdio_mux_init(struct device *dev,
 	}
 
 	dev_err(dev, "Error: No acceptable child buses found\n");
+
+err_loop:
+	mdio_mux_uninit_children(pb);
+	of_node_put(child_bus_node);
 err_pb_kz:
 	put_device(&parent_bus->dev);
 err_parent_bus:
@@ -192,14 +206,8 @@ EXPORT_SYMBOL_GPL(mdio_mux_init);
 void mdio_mux_uninit(void *mux_handle)
 {
 	struct mdio_mux_parent_bus *pb = mux_handle;
-	struct mdio_mux_child_bus *cb = pb->children;
-
-	while (cb) {
-		mdiobus_unregister(cb->mii_bus);
-		mdiobus_free(cb->mii_bus);
-		cb = cb->next;
-	}
 
+	mdio_mux_uninit_children(pb);
 	put_device(&pb->mii_bus->dev);
 }
 EXPORT_SYMBOL_GPL(mdio_mux_uninit);
-- 
2.33.0.rc1.237.g0d66db33f3-goog

[PATCH net v3 3/3] net: mdio-mux: Handle -EPROBE_DEFER correctly

[Saravana Kannan]

When registering mdiobus children, if we get an -EPROBE_DEFER, we shouldn't
ignore it and continue registering the rest of the mdiobus children. This
would permanently prevent the deferring child mdiobus from working instead
of reattempting it in the future. So, if a child mdiobus needs to be
reattempted in the future, defer the entire mdio-mux initialization.

This fixes the issue where PHYs sitting under the mdio-mux aren't
initialized correctly if the PHY's interrupt controller is not yet ready
when the mdio-mux is being probed. Additional context in the link below.

Fixes: 0ca2997d1452 ("netdev/of/phy: Add MDIO bus multiplexer support.")
Link: https://lore.kernel.org/lkml/CAGETcx95kHrv8wA-O+-JtfH7H9biJEGJtijuPVN0V5dUKUAB3A@mail.gmail.com/#t
Signed-off-by: Saravana Kannan <saravanak@google.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Marc Zyngier <maz@kernel.org>
Tested-by: Marc Zyngier <maz@kernel.org>
Acked-by: Kevin Hilman <khilman@baylibre.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
---
 drivers/net/mdio/mdio-mux.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mdio/mdio-mux.c b/drivers/net/mdio/mdio-mux.c
index 13035e2685c4..ebd001f0eece 100644
--- a/drivers/net/mdio/mdio-mux.c
+++ b/drivers/net/mdio/mdio-mux.c
@@ -175,11 +175,15 @@ int mdio_mux_init(struct device *dev,
 		cb->mii_bus->write = mdio_mux_write;
 		r = of_mdiobus_register(cb->mii_bus, child_bus_node);
 		if (r) {
+			mdiobus_free(cb->mii_bus);
+			if (r == -EPROBE_DEFER) {
+				ret_val = r;
+				goto err_loop;
+			}
+			devm_kfree(dev, cb);
 			dev_err(dev,
 				"Error: Failed to register MDIO bus for child %pOF\n",
 				child_bus_node);
-			mdiobus_free(cb->mii_bus);
-			devm_kfree(dev, cb);
 		} else {
 			cb->next = pb->children;
 			pb->children = cb;
-- 
2.33.0.rc1.237.g0d66db33f3-goog

Re: [PATCH net v3 0/3] Clean up and fix error handling in mdio_mux_init()

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (refs/heads/master):

On Tue, 17 Aug 2021 20:38:00 -0700 you wrote:
> This patch series was started due to -EPROBE_DEFER not being handled
> correctly in mdio_mux_init() and causing issues [1]. While at it, I also
> did some more error handling fixes and clean ups. The -EPROBE_DEFER fix is
> the last patch.
> 
> Ideally, in the last patch we'd treat any error similar to -EPROBE_DEFER
> but I'm not sure if it'll break any board/platforms where some child
> mdiobus never successfully registers. If we treated all errors similar to
> -EPROBE_DEFER, then none of the child mdiobus will work and that might be a
> regression. If people are sure this is not a real case, then I can fix up
> the last patch to always fail the entire mdio-mux init if any of the child
> mdiobus registration fails.
> 
> [...]

Here is the summary with links:
  - [net,v3,1/3] net: mdio-mux: Delete unnecessary devm_kfree
    https://git.kernel.org/netdev/net/c/663d946af5fb
  - [net,v3,2/3] net: mdio-mux: Don't ignore memory allocation errors
    https://git.kernel.org/netdev/net/c/99d81e942474
  - [net,v3,3/3] net: mdio-mux: Handle -EPROBE_DEFER correctly
    https://git.kernel.org/netdev/net/c/7bd0cef5dac6

You are awesome, thank you!
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