[PATCH net-next v5 01/11] net: stmmac: move XPCS lifetime management to platform drivers
netdev-bot+sashiko at kernel.org
netdev-bot+sashiko at kernel.org
Mon Sep 14 13:24:35 PDT 2026
Thank you for your contribution! Sashiko AI review found 3 potential
issue(s) to consider:
Critical: 0 · High: 0 · Medium: 2 · Low: 1
- [Medium] Commit message mischaracterizes the removal of the generic
XPCS creation as removing dead code.
- [Medium] DT binding vs implementation mismatch: after this patch
nothing in the stmmac core reads the generic 'pcs-handle' property,…
- [Low] The commit message describes two defects, one framed as "more
critically" (the common code overwriting priv->hw->xpcs after a…
--
net: stmmac: move XPCS lifetime management to platform drivers
The generic XPCS creation in stmmac_pcs_setup() (pcs-handle lookup and
mdio_bus_data->pcs_mask based xpcs_create_mdiodev()) is removed, leaving
only the plat->pcs_init() / plat->pcs_exit() dispatch. The Intel mGbE glue
grows its own pcs_init()/pcs_exit() that create and destroy the XPCS, and
the renesas-gbeth, rzn1 and socfpga pcs_exit() callbacks now clear
priv->hw->phylink_pcs after destroying the PCS.
A few questions on the commit message and on the removal of the generic
path.
> First, if a device tree specifies a "pcs-handle" but no select_pcs()
> callback is provided by the platform driver, the created XPCS is never
> used. The phylink framework requires select_pcs() to actually return
> the PCS to the core, so the pcs-handle property becomes effectively
> useless without the matching callback.
[Severity: Medium]
Is "the created XPCS is never used" accurate? An XPCS stored in
priv->hw->xpcs has two consumers that do not go through select_pcs().
stmmac_phylink_setup() in stmmac_main.c uses it to widen the phylink
interface sets:
/* If we have an xpcs, it defines which PHY interfaces are supported. */
if (priv->hw->xpcs)
pcs = xpcs_to_phylink_pcs(priv->hw->xpcs);
else
pcs = priv->hw->phylink_pcs;
if (pcs)
phy_interface_or(config->supported_interfaces, ...
and stmmac_init_phy() uses it to decide whether to attach a PHY at all:
if (priv->hw->xpcs &&
xpcs_get_an_mode(priv->hw->xpcs, mode) == DW_AN_C73)
return 0;
So for a dwmac instance with a pcs-handle but no plat->pcs_init, does this
change narrow config->supported_interfaces (and config->lpi_interfaces) and
alter the PHY-attach decision, rather than just dropping something unused?
Would it be worth spelling that behavioural change out in the commit
message?
> Second, and more critically, when a platform driver sets pcs_init()
> and creates an XPCS inside that callback, the common code afterwards
> still runs unconditionally and overwrites priv->hw->xpcs with the
> local xpcs variable, which stays NULL. The platform driver has no way
> to prevent this override because the common code runs after the
> platform-specific initialization.
[Severity: Low]
This isn't a bug, but could this paragraph say that no in-tree platform is
affected today?
All three pre-existing pcs_init() implementations store their PCS in
priv->hw->phylink_pcs, not priv->hw->xpcs:
renesas_gmac_pcs_init() -> priv->hw->phylink_pcs = miic_create(...)
rzn1_dwmac_pcs_init() -> priv->hw->phylink_pcs = miic_create(...)
socfpga_dwmac_pcs_init() -> priv->hw->phylink_pcs = pcs
so the old "priv->hw->xpcs = xpcs;" on the pcs_init branch overwrote NULL
with NULL. intel_mgbe_pcs_init() added here is the first in-tree pcs_init()
that stores an XPCS, which makes this a refactor that removes a latent trap
rather than a fix for observable breakage.
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c
> index f5f9fa67ecd77..4308dccbf2570 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c
> @@ -603,13 +603,47 @@ static void common_default_data(struct plat_stmmacenet_data *plat)
> plat->mdio_bus_data->needs_reset = true;
> }
>
> +static int intel_mgbe_pcs_init(struct stmmac_priv *priv)
> +{
> + struct fwnode_handle *devnode, *pcsnode;
> + struct dw_xpcs *xpcs;
> + int addr;
> +
> + devnode = dev_fwnode(priv->device);
> +
> + if (fwnode_property_present(devnode, "pcs-handle")) {
> + pcsnode = fwnode_find_reference(devnode, "pcs-handle", 0);
> + xpcs = xpcs_create_fwnode(pcsnode);
> + fwnode_handle_put(pcsnode);
> + } else {
> + addr = ffs(priv->plat->mdio_bus_data->pcs_mask) - 1;
> + xpcs = xpcs_create_mdiodev(priv->mii, addr);
> + }
> +
> + if (IS_ERR(xpcs))
> + return PTR_ERR(xpcs);
> +
> + xpcs_config_eee_mult_fact(xpcs, priv->plat->mult_fact_100ns);
> +
> + priv->hw->xpcs = xpcs;
> + return 0;
> +}
> +
[ ... ]
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
> index afe98ff5bdcb0..7396b68899c66 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
> @@ -426,35 +426,14 @@ int stmmac_mdio_reset(struct mii_bus *bus)
> int stmmac_pcs_setup(struct net_device *ndev)
> {
> struct stmmac_priv *priv = netdev_priv(ndev);
> - struct fwnode_handle *devnode, *pcsnode;
> - struct dw_xpcs *xpcs = NULL;
> - int addr, ret;
> -
> - devnode = dev_fwnode(priv->device);
> -
> - if (priv->plat->pcs_init) {
> - ret = priv->plat->pcs_init(priv);
> - } else if (fwnode_property_present(devnode, "pcs-handle")) {
> - pcsnode = fwnode_find_reference(devnode, "pcs-handle", 0);
> - xpcs = xpcs_create_fwnode(pcsnode);
> - fwnode_handle_put(pcsnode);
> - ret = PTR_ERR_OR_ZERO(xpcs);
> - } else if (priv->plat->mdio_bus_data &&
> - priv->plat->mdio_bus_data->pcs_mask) {
> - addr = ffs(priv->plat->mdio_bus_data->pcs_mask) - 1;
> - xpcs = xpcs_create_mdiodev(priv->mii, addr);
> - ret = PTR_ERR_OR_ZERO(xpcs);
> - } else {
> + int ret;
> +
> + if (!priv->plat->pcs_init)
> return 0;
> - }
>
> + ret = priv->plat->pcs_init(priv);
> if (ret)
> - return dev_err_probe(priv->device, ret, "No xPCS found\n");
> -
> - if (xpcs)
> - xpcs_config_eee_mult_fact(xpcs, priv->plat->mult_fact_100ns);
> -
> - priv->hw->xpcs = xpcs;
> + return dev_err_probe(priv->device, ret, "Failed to initialize PCS\n");
>
> return 0;
> }
[Severity: Medium]
After this change, does anything in the stmmac core still read the generic
"pcs-handle" property?
The property is still documented generically in
Documentation/devicetree/bindings/net/ethernet-controller.yaml:
pcs-handle:
$ref: /schemas/types.yaml#/definitions/phandle-array
items:
maxItems: 1
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.
and snps,dwmac.yaml $refs ethernet-controller.yaml and ends with
"additionalProperties: true", so pcs-handle stays schema-valid on every
dwmac node regardless of which glue is bound.
On a glue that does not set plat->pcs_init, stmmac_pcs_setup() now returns 0
without looking at the property, priv->hw->xpcs stays NULL, and nothing is
logged - whereas the removed code would at least fail probe with
"No xPCS found" for a bad phandle. Should the binding be updated to say
pcs-handle is only honoured by specific glue drivers, or should the core
keep a generic path (or emit a warning) so the two agree?
The same question applies to struct stmmac_mdio_bus_data.pcs_mask.
stmmac_mdio_register() still treats it as "a PCS lives at these MDIO
addresses" and masks them out of the bus scan:
new_bus->phy_mask = mdio_bus_data->phy_mask | mdio_bus_data->pcs_mask;
but no core code creates a PCS for those addresses any more, only
dwmac-intel's private intel_mgbe_pcs_init(). Does a glue that sets
pcs_mask without pcs_init now end up with that address neither scanned as a
PHY nor instantiated as a PCS?
--
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260913185849.907479-1-coiaprant%40gmail.com
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