[PATCH net-next v2] net: phy: motorcomm: enable the reference clock for YT8521 and YT8531

[Gavin Gao]

Hi Jiaxing,

Thanks for folding in YT8521 support.

I tested this on a PicoCOM RK3576 ACP board with a Motorcomm YT8521 PHY.
The 25 MHz reference clock from RK3576 REFCLKO25M_GMACx_OUT stays active,
and Ethernet works.

Tested-by: Gavin Gao <attinagaoxu at gmail.com>

Thanks,
Gavin

On Tue, Jul 28, 2026 at 5:04 AM Jiaxing Hu <gahing at gahingwoo.com> wrote:
>
> These PHYs need a 25 MHz reference. On boards without a local crystal
> it is fed from the SoC and described as a clock on the PHY node. Get and
> enable it in probe, via a small helper called from both yt8521_probe and
> yt8531_probe, so the PHY is clocked before its registers are accessed.
> The clock is optional, so crystal-clocked boards are unaffected.
>
> Reviewed-by: Andrew Lunn <andrew at lunn.ch>
> Signed-off-by: Jiaxing Hu <gahing at gahingwoo.com>
> ---
>
> Changes in v2:
> - Factor the clock enable into ytphy_get_and_enable_refclk() and call it
>   from yt8521_probe as well, so the YT8521 is covered too, not only the
>   YT8531. v1 only touched yt8531_probe.
> - Carried Andrew's Reviewed-by; the enable itself is unchanged, only
>   moved into the helper.
>
> v1: https://lore.kernel.org/all/20260719034555.3623003-1-gahing@gahingwoo.com/
>
> A second crystal-less RK3576 board with a YT8521 needs the same handling
> (see the RK3576 GMAC 25M refout thread [1]), so v2 covers both PHYs. This
> supersedes the withdrawn dwmac-rk MAC-side series. The DTS that consumes
> the clock (rk3576-armsom-cm5) goes to the rockchip tree separately; the
> clock is optional so this patch stands alone. The YT8531 path is tested
> on an ArmSoM CM5-IO (links at 1000 Mbit/s).
>
> [1] https://lore.kernel.org/all/20260727021048.3375444-1-attinagaoxu@gmail.com/
>
>  drivers/net/phy/motorcomm.c | 33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
>
> diff --git a/drivers/net/phy/motorcomm.c b/drivers/net/phy/motorcomm.c
> index 708491bc1..32eb5ce93 100644
> --- a/drivers/net/phy/motorcomm.c
> +++ b/drivers/net/phy/motorcomm.c
> @@ -6,6 +6,7 @@
>   * Author: Frank <Frank.Sae at motor-comm.com>
>   */
>
> +#include <linux/clk.h>
>  #include <linux/etherdevice.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
> @@ -1043,6 +1044,29 @@ static int yt8531_set_ds(struct phy_device *phydev)
>         return 0;
>  }
>
> +/**
> + * ytphy_get_and_enable_refclk() - get and enable the PHY reference clock
> + * @phydev: a pointer to a &struct phy_device
> + *
> + * A crystal-less YT8521/YT8531 takes its 25 MHz reference from the SoC. When
> + * that reference is described as a clock, enable it for the life of the
> + * device. It is optional, so crystal-clocked boards are unaffected.
> + *
> + * returns 0 or negative errno code
> + */
> +static int ytphy_get_and_enable_refclk(struct phy_device *phydev)
> +{
> +       struct device *dev = &phydev->mdio.dev;
> +       struct clk *clk;
> +
> +       clk = devm_clk_get_optional_enabled(dev, NULL);
> +       if (IS_ERR(clk))
> +               return dev_err_probe(dev, PTR_ERR(clk),
> +                                    "failed to get and enable the reference clock\n");
> +
> +       return 0;
> +}
> +
>  /**
>   * yt8521_probe() - read chip config then set suitable polling_mode
>   * @phydev: a pointer to a &struct phy_device
> @@ -1064,6 +1088,10 @@ static int yt8521_probe(struct phy_device *phydev)
>
>         phydev->priv = priv;
>
> +       ret = ytphy_get_and_enable_refclk(phydev);
> +       if (ret)
> +               return ret;
> +
>         chip_config = ytphy_read_ext_with_lock(phydev, YT8521_CHIP_CONFIG_REG);
>         if (chip_config < 0)
>                 return chip_config;
> @@ -1171,6 +1199,11 @@ static int yt8531_probe(struct phy_device *phydev)
>         struct device *dev = &phydev->mdio.dev;
>         u16 mask, val;
>         u32 freq;
> +       int ret;
> +
> +       ret = ytphy_get_and_enable_refclk(phydev);
> +       if (ret)
> +               return ret;
>
>         if (device_property_read_u32(dev, "motorcomm,clk-out-frequency-hz", &freq))
>                 freq = YTPHY_DTS_OUTPUT_CLK_DIS;
> --
> 2.43.0
>