Re: [PATCH 12/26] net: stmmac: dwmac-qcom-ethqos: add support for the optional serdes phy

[Bartosz Golaszewski]

On Mon, Jun 12, 2023 at 10:33 PM Andrew Halaney <ahalaney@xxxxxxxxxx> wrote:
>
> On Mon, Jun 12, 2023 at 11:23:41AM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> >
> > On sa8775p platforms, there's a SGMII SerDes PHY between the MAC and
> > external PHY that we need to enable and configure.
> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> > ---
> >  .../stmicro/stmmac/dwmac-qcom-ethqos.c        | 37 +++++++++++++++++++
> >  1 file changed, 37 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c
> > index 8ed05f29fe8b..3438b6229351 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c
> > @@ -6,6 +6,7 @@
> >  #include <linux/of_device.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/phy.h>
> > +#include <linux/phy/phy.h>
> >  #include <linux/property.h>
> >
> >  #include "stmmac.h"
> > @@ -93,6 +94,7 @@ struct qcom_ethqos {
> >
> >       unsigned int rgmii_clk_rate;
> >       struct clk *rgmii_clk;
> > +     struct phy *serdes_phy;
> >       unsigned int speed;
> >
> >       const struct ethqos_emac_por *por;
> > @@ -566,6 +568,30 @@ static void ethqos_fix_mac_speed(void *priv, unsigned int speed)
> >       ethqos_configure(ethqos);
> >  }
> >
> > +static int qcom_ethqos_serdes_powerup(struct net_device *ndev, void *priv)
> > +{
> > +     struct qcom_ethqos *ethqos = priv;
> > +     int ret;
> > +
> > +     ret = phy_set_speed(ethqos->serdes_phy, ethqos->speed);
> > +     if (ret)
> > +             return ret;
> > +
> > +     ret = phy_init(ethqos->serdes_phy);
> > +     if (ret)
> > +             return ret;
> > +
> > +     return phy_power_on(ethqos->serdes_phy);
>
> The docs say (phy.rst):
>
>     The general order of calls should be::
>
>         [devm_][of_]phy_get()
>         phy_init()
>         phy_power_on()
>         [phy_set_mode[_ext]()]
>         ...
>         phy_power_off()
>         phy_exit()
>         [[of_]phy_put()]
>
>     Some PHY drivers may not implement :c:func:`phy_init` or :c:func:`phy_power_on`,
>     but controllers should always call these functions to be compatible with other
>     PHYs. Some PHYs may require :c:func:`phy_set_mode <phy_set_mode_ext>`, while
>     others may use a default mode (typically configured via devicetree or other
>     firmware). For compatibility, you should always call this function if you know
>     what mode you will be using. Generally, this function should be called after
>     :c:func:`phy_power_on`, although some PHY drivers may allow it at any time.
>
> Not really dictating you need to do that order, but if possible I think
> calling phy_set_speed after init + power_on is more generic. Not sure if
> that plays nice with the phy driver in this series or not.
>
> Otherwise, I think this looks good.
>

I had to rework the PHY driver code a bit for this order to work but
it'll be good now in v2.

Thanks!
Bart

> > +}
> > +
> > +static void qcom_ethqos_serdes_powerdown(struct net_device *ndev, void *priv)
> > +{
> > +     struct qcom_ethqos *ethqos = priv;
> > +
> > +     phy_power_off(ethqos->serdes_phy);
> > +     phy_exit(ethqos->serdes_phy);
> > +}
> > +
> >  static int ethqos_clks_config(void *priv, bool enabled)
> >  {
> >       struct qcom_ethqos *ethqos = priv;
> > @@ -651,6 +677,12 @@ static int qcom_ethqos_probe(struct platform_device *pdev)
> >       if (ret)
> >               goto out_config_dt;
> >
> > +     ethqos->serdes_phy = devm_phy_optional_get(dev, "serdes");
> > +     if (IS_ERR(ethqos->serdes_phy)) {
> > +             ret = PTR_ERR(ethqos->serdes_phy);
> > +             goto out_config_dt;
> > +     }
> > +
> >       ethqos->speed = SPEED_1000;
> >       ethqos_update_rgmii_clk(ethqos, SPEED_1000);
> >       ethqos_set_func_clk_en(ethqos);
> > @@ -666,6 +698,11 @@ static int qcom_ethqos_probe(struct platform_device *pdev)
> >       if (of_device_is_compatible(np, "qcom,qcs404-ethqos"))
> >               plat_dat->rx_clk_runs_in_lpi = 1;
> >
> > +     if (ethqos->serdes_phy) {
> > +             plat_dat->serdes_powerup = qcom_ethqos_serdes_powerup;
> > +             plat_dat->serdes_powerdown  = qcom_ethqos_serdes_powerdown;
> > +     }
> > +
> >       ret = stmmac_dvr_probe(dev, plat_dat, &stmmac_res);
> >       if (ret)
> >               goto out_config_dt;
> > --
> > 2.39.2
> >
>