netdev - Re: PHY reset may still be asserted during MDIO probe

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Date:   Fri, 9 Jul 2021 21:14:18 +0300
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>
CC:     netdev <netdev@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: PHY reset may still be asserted during MDIO probe



On 09/07/2021 18:33, Geert Uytterhoeven wrote:
> Hi all,
> 
> I'm investigating a network failure after kexec on the Renesas Koelsch
> and Salvator-XS development boards, using the sh-eth or ravb driver.
> 
> During normal boot, the Ethernet interface is working fine:
> 
>      libphy: get_phy_c22_id:814: sh_mii: mdiobus_read() MII_PHYSID1 returned 34
>      libphy: get_phy_c22_id:824: sh_mii: mdiobus_read() MII_PHYSID2 returned 5431
>      libphy: get_phy_c22_id:832: sh_mii: phy_id = 0x00221537
>      libphy: get_phy_device:895: sh_mii: get_phy_c22_id() returned 0
>      fwnode_mdiobus_register_phy:109: sh_mii: get_phy_device() returned (ptrval)
>      fwnode_mdiobus_phy_device_register:46: sh_mii: fwnode_irq_get() returned 191
>      libphy: mdiobus_register_gpiod:48: mdiodev->reset_gpio = (ptrval)
>      mdio_bus ee700000.ethernet-ffffffff:01:
> mdiobus_register_device:88: assert MDIO reset
>      libphy: mdio_device_reset:124: calling gpiod_set_value_cansleep(..., 1)
>      mdio_bus ee700000.ethernet-ffffffff:01: phy_device_register:931:
> deassert PHY reset
>      libphy: mdio_device_reset:124: calling gpiod_set_value_cansleep(..., 0)
>      Micrel KSZ8041RNLI ee700000.ethernet-ffffffff:01: phy_probe:3026:
> deassert PHY reset
>      libphy: mdio_device_reset:124: calling gpiod_set_value_cansleep(..., 0)
>      fwnode_mdiobus_phy_device_register:75: sh_mii:
> phy_device_register() returned 0
>      fwnode_mdiobus_register_phy:137: sh_mii:
> fwnode_mdiobus_phy_device_register() returned 0
>      of_mdiobus_register:188: of_mdiobus_register_phy(sh_mii,
> /soc/ethernet@...00000/ethernet-phy@1, 1) returned 0
>      sh-eth ee700000.ethernet eth0: Base address at 0xee700000,
> 2e:09:0a:00:6d:85, IRQ 126.
> 
> When using kexec, the PHY reset is asserted before starting the
> new kernel:
> 
>      Micrel KSZ8041RNLI ee700000.ethernet-ffffffff:01: phy_detach:1759:
> assert PHY reset
>      libphy: mdio_device_reset:124: calling gpiod_set_value_cansleep(..., 1)
>      kexec_core: Starting new kernel
>      Bye!
> 
> The new kernel fails to probe the PHY, as the PHY reset is still
> asserted:
> 
>      libphy: get_phy_c22_id:814: sh_mii: mdiobus_read() MII_PHYSID1
> returned 65535
>      libphy: get_phy_c22_id:824: sh_mii: mdiobus_read() MII_PHYSID2
> returned 65535
>      libphy: get_phy_c22_id:832: sh_mii: phy_id = 0xffffffff
>      libphy: get_phy_device:895: sh_mii: get_phy_c22_id() returned -19
>      fwnode_mdiobus_register_phy:109: sh_mii: get_phy_device() returned -ENODEV
>      of_mdiobus_register:188: of_mdiobus_register_phy(sh_mii,
> /soc/ethernet@...00000/ethernet-phy@1, 1) returned -19
>      mdio_bus ee700000.ethernet-ffffffff: MDIO device at address 1 is missing.
>      sh-eth ee700000.ethernet eth0: Base address at 0xee700000,
> 2e:09:0a:00:6d:85, IRQ 126.
> 
> This issue can also be reproduced using unbind:
> 
>      # echo ee700000.ethernet > /sys/bus/platform/drivers/sh-eth/unbind
>      sh-eth ee700000.ethernet eth0: Link is Down
>      Micrel KSZ8041RNLI ee700000.ethernet-ffffffff:01: phy_detach:1759:
> assert PHY reset
>      libphy: mdio_device_reset:124: calling gpiod_set_value_cansleep(..., 1)
>      Micrel KSZ8041RNLI ee700000.ethernet-ffffffff:01: phy_remove:3120:
> assert PHY reset
>      libphy: mdio_device_reset:124: calling gpiod_set_value_cansleep(..., 1)
>      mdio_bus ee700000.ethernet-ffffffff:01: phy_device_remove:974:
> assert PHY reset
>      libphy: mdio_device_reset:124: calling gpiod_set_value_cansleep(..., 1)
> 
> and bind:
> 
>      # echo ee700000.ethernet > /sys/bus/platform/drivers/sh-eth/bind
>      (same log as kexec boot)
> 
> I think fwnode_mdiobus_register_phy() should do the PHY reset (assert +
> deassert) before calling get_phy_device(), but currently that happens
> in phy_device_register(), which is called later.

Seems like similar to [1], only PHY ID in DT compatible is current w/a.

[1] https://lkml.org/lkml/2020/10/23/750

-- 
Best regards,
grygorii