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net: phy: mdio_device: Reset device only when necessary

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Currently the phy reset sequence is as shown below for a
devicetree described mdio phy on boot:

1. Assert the phy_device's reset as part of registering
2. Deassert the phy_device's reset as part of registering
3. Deassert the phy_device's reset as part of phy_probe
4. Deassert the phy_device's reset as part of phy_hw_init

The extra two deasserts include waiting the deassert delay afterwards,
which is adding unnecessary delay.

This applies to both possible types of resets (reset controller
reference and a reset gpio) that can be used.

Here's some snipped tracing output using the following command line
params "trace_event=gpio:* trace_options=stacktrace" illustrating
the reset handling and where its coming from:

    /* Assert */
       systemd-udevd-283     [002] .....     6.780434: gpio_value: 544 set 0
       systemd-udevd-283     [002] .....     6.783849: <stack trace>
     => gpiod_set_raw_value_commit
     => gpiod_set_value_nocheck
     => gpiod_set_value_cansleep
     => mdio_device_reset
     => mdiobus_register_device
     => phy_device_register
     => fwnode_mdiobus_phy_device_register
     => fwnode_mdiobus_register_phy
     => __of_mdiobus_register
     => stmmac_mdio_register
     => stmmac_dvr_probe
     => stmmac_pltfr_probe
     => devm_stmmac_pltfr_probe
     => qcom_ethqos_probe
     => platform_probe

    /* Deassert */
       systemd-udevd-283     [002] .....     6.802480: gpio_value: 544 set 1
       systemd-udevd-283     [002] .....     6.805886: <stack trace>
     => gpiod_set_raw_value_commit
     => gpiod_set_value_nocheck
     => gpiod_set_value_cansleep
     => mdio_device_reset
     => phy_device_register
     => fwnode_mdiobus_phy_device_register
     => fwnode_mdiobus_register_phy
     => __of_mdiobus_register
     => stmmac_mdio_register
     => stmmac_dvr_probe
     => stmmac_pltfr_probe
     => devm_stmmac_pltfr_probe
     => qcom_ethqos_probe
     => platform_probe

    /* Deassert */
       systemd-udevd-283     [002] .....     6.882601: gpio_value: 544 set 1
       systemd-udevd-283     [002] .....     6.886014: <stack trace>
     => gpiod_set_raw_value_commit
     => gpiod_set_value_nocheck
     => gpiod_set_value_cansleep
     => mdio_device_reset
     => phy_probe
     => really_probe
     => __driver_probe_device
     => driver_probe_device
     => __device_attach_driver
     => bus_for_each_drv
     => __device_attach
     => device_initial_probe
     => bus_probe_device
     => device_add
     => phy_device_register
     => fwnode_mdiobus_phy_device_register
     => fwnode_mdiobus_register_phy
     => __of_mdiobus_register
     => stmmac_mdio_register
     => stmmac_dvr_probe
     => stmmac_pltfr_probe
     => devm_stmmac_pltfr_probe
     => qcom_ethqos_probe
     => platform_probe

    /* Deassert */
      NetworkManager-477     [000] .....     7.023144: gpio_value: 544 set 1
      NetworkManager-477     [000] .....     7.026596: <stack trace>
     => gpiod_set_raw_value_commit
     => gpiod_set_value_nocheck
     => gpiod_set_value_cansleep
     => mdio_device_reset
     => phy_init_hw
     => phy_attach_direct
     => phylink_fwnode_phy_connect
     => __stmmac_open
     => stmmac_open

There's a lot of paths where the device is getting its reset
asserted and deasserted. Let's track the state and only actually
do the assert/deassert when it changes.

Reported-by: Sagar Cheluvegowda <quic_scheluve@quicinc.com>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20231127-net-phy-reset-once-v2-1-448e8658779e@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Andrew Halaney 2023-11-27 15:41:10 -06:00 committed by Jakub Kicinski
parent 753c8608f3
commit df16c1c51d
3 changed files with 8 additions and 0 deletions
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6
drivers/net/phy/mdio_device.c
View file

@ -62,6 +62,7 @@ struct mdio_device *mdio_device_create(struct mii_bus *bus, int addr)
mdiodev->device_remove = mdio_device_remove;
mdiodev->bus = bus;
mdiodev->addr = addr;
mdiodev->reset_state = -1;
dev_set_name(&mdiodev->dev, PHY_ID_FMT, bus->id, addr);
@ -122,6 +123,9 @@ void mdio_device_reset(struct mdio_device *mdiodev, int value)
if (!mdiodev->reset_gpio && !mdiodev->reset_ctrl)
return;
if (mdiodev->reset_state == value)
return;
if (mdiodev->reset_gpio)
gpiod_set_value_cansleep(mdiodev->reset_gpio, value);
@ -135,6 +139,8 @@ void mdio_device_reset(struct mdio_device *mdiodev, int value)
d = value ? mdiodev->reset_assert_delay : mdiodev->reset_deassert_delay;
if (d)
fsleep(d);
mdiodev->reset_state = value;
}
EXPORT_SYMBOL(mdio_device_reset);

1
drivers/net/phy/phy_device.c
View file

@ -654,6 +654,7 @@ struct phy_device *phy_device_create(struct mii_bus *bus, int addr, u32 phy_id,
mdiodev->flags = MDIO_DEVICE_FLAG_PHY;
mdiodev->device_free = phy_mdio_device_free;
mdiodev->device_remove = phy_mdio_device_remove;
mdiodev->reset_state = -1;
dev->speed = SPEED_UNKNOWN;
dev->duplex = DUPLEX_UNKNOWN;

1
include/linux/mdio.h
View file

@ -38,6 +38,7 @@ struct mdio_device {
/* Bus address of the MDIO device (0-31) */
int addr;
int flags;
int reset_state;
struct gpio_desc *reset_gpio;
struct reset_control *reset_ctrl;
unsigned int reset_assert_delay;