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net: macb: Avoid 20s boot delay by skipping MDIO bus registration for fixed-link PHY

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A boot delay was introduced by commit 79540d133e ("net: macb: Fix
handling of fixed-link node"). This delay was caused by the call to
`mdiobus_register()` in cases where a fixed-link PHY was present. The
MDIO bus registration triggered unnecessary PHY address scans, leading
to a 20-second delay due to attempts to detect Clause 45 (C45)
compatible PHYs, despite no MDIO bus being attached.

The commit 79540d133e ("net: macb: Fix handling of fixed-link node")
was originally introduced to fix a regression caused by commit
7897b071ac ("net: macb: convert to phylink"), which caused the driver
to misinterpret fixed-link nodes as PHY nodes. This resulted in warnings
like:
mdio_bus f0028000.ethernet-ffffffff: fixed-link has invalid PHY address
mdio_bus f0028000.ethernet-ffffffff: scan phy fixed-link at address 0
...
mdio_bus f0028000.ethernet-ffffffff: scan phy fixed-link at address 31

This patch reworks the logic to avoid registering and allocation of the
MDIO bus when:
  - The device tree contains a fixed-link node.
  - There is no "mdio" child node in the device tree.

If a child node named "mdio" exists, the MDIO bus will be registered to
support PHYs  attached to the MACB's MDIO bus. Otherwise, with only a
fixed-link, the MDIO bus is skipped.

Tested on a sama5d35 based system with a ksz8863 switch attached to
macb0.

Fixes: 79540d133e ("net: macb: Fix handling of fixed-link node")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: stable@vger.kernel.org
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20241013052916.3115142-1-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Oleksij Rempel 2024-10-13 07:29:16 +02:00 committed by Jakub Kicinski
parent cf57b5d7a2
commit d0c3601f2c
1 changed files with 11 additions and 3 deletions
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14
drivers/net/ethernet/cadence/macb_main.c
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@ -930,9 +930,6 @@ static int macb_mdiobus_register(struct macb *bp)
return ret;
}
if (of_phy_is_fixed_link(np))
return mdiobus_register(bp->mii_bus);
/* Only create the PHY from the device tree if at least one PHY is
* described. Otherwise scan the entire MDIO bus. We do this to support
* old device tree that did not follow the best practices and did not
@ -953,8 +950,19 @@ static int macb_mdiobus_register(struct macb *bp)
static int macb_mii_init(struct macb *bp)
{
struct device_node *child, *np = bp->pdev->dev.of_node;
int err = -ENXIO;
/* With fixed-link, we don't need to register the MDIO bus,
* except if we have a child named "mdio" in the device tree.
* In that case, some devices may be attached to the MACB's MDIO bus.
*/
child = of_get_child_by_name(np, "mdio");
if (child)
of_node_put(child);
else if (of_phy_is_fixed_link(np))
return macb_mii_probe(bp->dev);
/* Enable management port */
macb_writel(bp, NCR, MACB_BIT(MPE));