RE: [PATCH v5 net-next 3/3] net: axienet: set mdio clock according to bus-frequency

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> -----Original Message-----
> From: Andy Chiu <andy.chiu@xxxxxxxxxx>
> Sent: Thursday, November 17, 2022 9:10 PM
> To: davem@xxxxxxxxxxxxx; andrew@xxxxxxx; kuba@xxxxxxxxxx;
> michal.simek@xxxxxxxxxx; radhey.shyam.pandey@xxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx; pabeni@xxxxxxxxxx;
> edumazet@xxxxxxxxxx; andy.chiu@xxxxxxxxxx; greentime.hu@xxxxxxxxxx
> Subject: [PATCH v5 net-next 3/3] net: axienet: set mdio clock according to
> bus-frequency
> 
> CAUTION: This message has originated from an External Source. Please use
> proper judgment and caution when opening attachments, clicking links, or
> responding to this email.
> 
> 
> Some FPGA platforms have 80KHz MDIO bus frequency constraint when
> connecting Ethernet to its on-board external Marvell PHY. Thus, we may have
> to set MDIO clock according to the DT. Otherwise, use the default
> 2.5 MHz, as specified by 802.3, if the entry is not present.
> 
> Also, change MAX_MDIO_FREQ to DEFAULT_MDIO_FREQ because we may
> actually set MDIO bus frequency higher than 2.5MHz if undelying devices
> support it. And properly disable the mdio bus clock in error path.
> 
> Signed-off-by: Andy Chiu <andy.chiu@xxxxxxxxxx>
> ---
>  .../net/ethernet/xilinx/xilinx_axienet_mdio.c | 70 +++++++++++++------
>  1 file changed, 49 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
> b/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
> index e1f51a071888..2f07fde361aa 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
> @@ -17,7 +17,7 @@
> 
>  #include "xilinx_axienet.h"
> 
> -#define MAX_MDIO_FREQ          2500000 /* 2.5 MHz */
> +#define DEFAULT_MDIO_FREQ      2500000 /* 2.5 MHz */
>  #define DEFAULT_HOST_CLOCK     150000000 /* 150 MHz */
> 
>  /* Wait till MDIO interface is ready to accept a new transaction.*/ @@ -
> 147,15 +147,20 @@ static int axienet_mdio_write(struct mii_bus *bus, int
> phy_id, int reg,
>  /**
>   * axienet_mdio_enable - MDIO hardware setup function
>   * @lp:                Pointer to axienet local data structure.
> + * @np:                Pointer to mdio device tree node.
>   *
> - * Return:     0 on success, -ETIMEDOUT on a timeout.
> + * Return:     0 on success, -ETIMEDOUT on a timeout, -EOVERFLOW on a
> clock
> + *             divisor overflow.
>   *
>   * Sets up the MDIO interface by initializing the MDIO clock and enabling the
>   * MDIO interface in hardware.
>   **/
> -static int axienet_mdio_enable(struct axienet_local *lp)
> +static int axienet_mdio_enable(struct axienet_local *lp, struct
> +device_node *np)
>  {
> +       u32 mdio_freq = DEFAULT_MDIO_FREQ;
>         u32 host_clock;
> +       u32 clk_div;
> +       int ret;
> 
>         lp->mii_clk_div = 0;
> 
> @@ -184,6 +189,12 @@ static int axienet_mdio_enable(struct axienet_local
> *lp)
>                             host_clock);
>         }
> 
> +       if (np)
> +               of_property_read_u32(np, "clock-frequency", &mdio_freq);
> +       if (mdio_freq != DEFAULT_MDIO_FREQ)
> +               netdev_info(lp->ndev, "Setting non-standard mdio bus frequency
> to %u Hz\n",
> +                           mdio_freq);
> +
>         /* clk_div can be calculated by deriving it from the equation:
>          * fMDIO = fHOST / ((1 + clk_div) * 2)
>          *
> @@ -209,29 +220,42 @@ static int axienet_mdio_enable(struct axienet_local
> *lp)
>          * "clock-frequency" from the CPU
>          */
> 
> -       lp->mii_clk_div = (host_clock / (MAX_MDIO_FREQ * 2)) - 1;
> +       clk_div = (host_clock / (mdio_freq * 2)) - 1;
>         /* If there is any remainder from the division of
> -        * fHOST / (MAX_MDIO_FREQ * 2), then we need to add
> -        * 1 to the clock divisor or we will surely be above 2.5 MHz
> +        * fHOST / (mdio_freq * 2), then we need to add
> +        * 1 to the clock divisor or we will surely be
> +        * above the requested frequency
>          */
> -       if (host_clock % (MAX_MDIO_FREQ * 2))
> -               lp->mii_clk_div++;
> +       if (host_clock % (mdio_freq * 2))
> +               clk_div++;
> +
> +       /* Check for overflow of mii_clk_div */
> +       if (clk_div & ~XAE_MDIO_MC_CLOCK_DIVIDE_MAX) {
> +               netdev_warn(lp->ndev, "MDIO clock divisor overflow\n");
> +               return -EOVERFLOW;
> +       }
> +       lp->mii_clk_div = (u8)clk_div;
> 
>         netdev_dbg(lp->ndev,
>                    "Setting MDIO clock divisor to %u/%u Hz host clock.\n",
>                    lp->mii_clk_div, host_clock);
> 
> -       axienet_iow(lp, XAE_MDIO_MC_OFFSET, lp->mii_clk_div |
> XAE_MDIO_MC_MDIOEN_MASK);
> +       axienet_mdio_mdc_enable(lp);
> 
> -       return axienet_mdio_wait_until_ready(lp);
> +       ret = axienet_mdio_wait_until_ready(lp);
> +       if (ret)
> +               axienet_mdio_mdc_disable(lp);
> +
> +       return ret;
>  }
> 
>  /**
>   * axienet_mdio_setup - MDIO setup function
>   * @lp:                Pointer to axienet local data structure.
>   *
> - * Return:     0 on success, -ETIMEDOUT on a timeout, -ENOMEM when
> - *             mdiobus_alloc (to allocate memory for mii bus structure) fails.
> + * Return:     0 on success, -ETIMEDOUT on a timeout, -EOVERFLOW on a
> clock
> + *             divisor overflow, -ENOMEM when mdiobus_alloc (to allocate
> + *             memory for mii bus structure) fails.
>   *
>   * Sets up the MDIO interface by initializing the MDIO clock.
>   * Register the MDIO interface.
> @@ -242,10 +266,6 @@ int axienet_mdio_setup(struct axienet_local *lp)
>         struct mii_bus *bus;
>         int ret;
> 
> -       ret = axienet_mdio_enable(lp);
> -       if (ret < 0)
> -               return ret;
> -
>         bus = mdiobus_alloc();
>         if (!bus)
>                 return -ENOMEM;
> @@ -261,15 +281,23 @@ int axienet_mdio_setup(struct axienet_local *lp)
>         lp->mii_bus = bus;
> 
>         mdio_node = of_get_child_by_name(lp->dev->of_node, "mdio");
> +       ret = axienet_mdio_enable(lp, mdio_node);
> +       if (ret < 0)
> +               goto unregister;
>         ret = of_mdiobus_register(bus, mdio_node);
> +       if (ret)
> +               goto unregister_mdio_enabled;
>         of_node_put(mdio_node);
> -       if (ret) {
> -               mdiobus_free(bus);
> -               lp->mii_bus = NULL;
> -               return ret;
> -       }
>         axienet_mdio_mdc_disable(lp);
>         return 0;
> +
> +unregister_mdio_enabled:
> +       axienet_mdio_mdc_disable(lp);
> +unregister:
> +       of_node_put(mdio_node);
> +       mdiobus_free(bus);
> +       lp->mii_bus = NULL;
> +       return ret;
>  }
> 
>  /**
> --
> 2.36.0

Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xxxxxxx>




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