Re: [PATCH net-next v3 1/9] net: phy: dp83867: add regulator supply management

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- [Medium] With CONFIG_REGULATOR=n, dp83867_power_on()
  (drivers/net/phy/dp83867.c) sleeps 200 ms on every probe, even when…
- [Medium] The patch makes the driver read four new DT properties
  (vdda-2p5-supply, vdd-1p0-supply, vdda-1p8-supply, vddio-supply)…
- [Low] The commit message says the driver sleeps 200 ms "when any supply
  is newly enabled".

--

net: phy: dp83867: add regulator supply management

This commit adds dp83867_power_on(), which enables up to four optional
supplies (vdda-2p5, vdd-1p0, vdda-1p8, vddio) at the start of
dp83867_probe(). If any supply is present, the driver sleeps for 200 ms
to meet the datasheet's post power-up stabilization requirement.

> diff --git a/drivers/net/phy/dp83867.c b/drivers/net/phy/dp83867.c
> index a3cd5cb11ea0a..092bc68bb9bc6 100644
> --- a/drivers/net/phy/dp83867.c
> +++ b/drivers/net/phy/dp83867.c

[ ... ]

> @@ -730,11 +731,42 @@ static int dp83867_resume(struct phy_device *phydev)
>  	return 0;
>  }
>  
> +static int dp83867_power_on(struct phy_device *phydev)
> +{
> +	static const char * const supply_names[] = {
> +		"vdda-2p5", "vdd-1p0", "vdda-1p8", "vddio",
> +	};

[Severity: Medium]
These names become four new DT properties: vdda-2p5-supply,
vdd-1p0-supply, vdda-1p8-supply and vddio-supply. Should
Documentation/devicetree/bindings/net/ti,dp83867.yaml document them in
the same series?

Right now the binding lists no *-supply properties and ends with:

  unevaluatedProperties: false

The only schema it references, ethernet-controller.yaml, has no supply
properties either. A node that uses the new properties won't validate
against this schema.

ti,dp83867.yaml has no select, so dtbs_check may never apply it to board
DTs. Even so, the properties would still be undocumented ABI.

A related question: should the binding also say that an
ethernet-phy-idXXXX.XXXX compatible is required when these rails are
switched? fwnode_mdiobus_register_phy() only skips the MDIO ID read when
that compatible is present:

drivers/net/mdio/fwnode_mdio.c:fwnode_mdiobus_register_phy() {
    ...
	if (is_c45 || fwnode_get_phy_id(child, &phy_id))
		phy = get_phy_device(bus, addr, is_c45);
	else
		phy = phy_device_create(bus, addr, phy_id, 0, NULL);
    ...
}

Without that compatible, get_phy_device() reads the ID from a PHY that
is not powered yet. The phy_device is then never created, so
dp83867_probe() never runs to turn the rails on.

> +	struct device *dev = &phydev->mdio.dev;
> +	bool supplies_enabled = false;
> +	int i, ret;
> +
> +	for (i = 0; i < ARRAY_SIZE(supply_names); i++) {
> +		ret = devm_regulator_get_enable_optional(dev, supply_names[i]);
> +		if (ret == -ENODEV)
> +			continue;

[Severity: Medium]
What happens here with CONFIG_REGULATOR=n? The stub returns 0, not
-ENODEV:

include/linux/regulator/consumer.h:
static inline int devm_regulator_get_enable_optional(struct device *dev,
						     const char *id)
{
	return 0;
}

In that case the -ENODEV check never matches and supplies_enabled is set
on the first iteration. fsleep(200000) then runs on every probe, even
when the board describes no supplies.

DP83867_PHY in drivers/net/phy/Kconfig doesn't depend on REGULATOR, so
this config is valid. Each probe attempt, including -EPROBE_DEFER
retries, would add 200 ms per PHY.

This doesn't match the commit message:

    Absent supplies are silently skipped, so boards
    that do not describe them are unaffected.

Would an IS_ENABLED(CONFIG_REGULATOR) check work here? Another option is
devm_regulator_get_optional() followed by an explicit enable, so the
sleep only runs when a real regulator was found.

> +		if (ret)
> +			return dev_err_probe(dev, ret,
> +					     "failed to enable %s supply\n",
> +					     supply_names[i]);
> +		supplies_enabled = true;

[Severity: Low]
The commit message says:

    When any supply is newly enabled the driver sleeps for 200 ms before
    returning.

Is "newly enabled" accurate? _devm_regulator_get_enable() returns the
result of regulator_enable():

drivers/regulator/devres.c:_devm_regulator_get_enable() {
    ...
	ret = regulator_enable(r);
	if (!ret)
		ret = devm_add_action_or_reset(dev, &regulator_action_disable, r);
    ...
}

That result is also 0 when the rail was already on. This covers
regulator-always-on, regulator-boot-on, a rail enabled by the
bootloader, or a rail shared with another consumer. So the 200 ms delay
runs whenever any supply is described, whatever its earlier state.

The rails are also enabled before dp83867_of_init(), which can fail with
-EPROBE_DEFER:

dp83867_probe()
  dp83867_of_init()
    dp83867_of_init_io_impedance()
      of_nvmem_cell_get() -> -EPROBE_DEFER

On that failure, devres runs regulator_action_disable for each enabled
supply and the PHY loses power.

Does each deferral then power-cycle the PHY and add another 200 ms on
the retry?

> +	}
> +
> +	/* Datasheet section 6.6 suggests a 200ms post power-up stabilization */
> +	if (supplies_enabled)
> +		fsleep(200000);
> +
> +	return 0;
> +}

[ ... ]

-- 
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20261017-shikra_ethernet-v3-0-26a8beb44b8f%40oss.qualcomm.com