[U-Boot] [PATCH 3/4] dm: net: macb: Implement link speed change callback

[Auer, Lukas]

Hi Bin,

On Thu, 2019-05-16 at 02:12 -0700, Bin Meng wrote:
> At present the link speed change callback is a nop. According to
> macb device tree bindings, an optional "tx_clk" is used to clock
> the ethernet controller's TX_CLK under different link speed.
> 
> In 10/100 MII mode, transmit logic must be clocked from a free
> running clock generated by the external PHY. In gigabit GMII mode,
> the controller, not the external PHY, must generate the 125 MHz
> transmit clock towards the PHY.
> 
> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
> ---
> 
>  drivers/net/macb.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/net/macb.c b/drivers/net/macb.c
> index b7f404e..7d86fa1 100644
> --- a/drivers/net/macb.c
> +++ b/drivers/net/macb.c
> @@ -497,6 +497,32 @@ static int macb_phy_find(struct macb_device *macb, const char *name)
>  #ifdef CONFIG_DM_ETH
>  int __weak macb_linkspd_cb(struct udevice *dev, unsigned int speed)
>  {
> +#ifdef CONFIG_CLK
> +	struct clk tx_clk;
> +	ulong rate;
> +	int ret;
> +
> +	ret = clk_get_by_name(dev, "tx_clk", &tx_clk);
> +	if (ret)
> +		return 0;

Can you return errors in ret here?

> +
> +	switch (speed) {
> +	case _10BASET:
> +		rate = 2500000;
> +		break;
> +	case _100BASET:
> +		rate = 25000000;
> +		break;
> +	case _1000BASET:
> +	default:
> +		rate = 125000000;
> +		break;

The Linux driver simply returns in the default case, without changing
tx_clk. I am wondering if we should do the same in U-Boot?

> +	}
> +
> +	if (tx_clk.dev)
> +		clk_set_rate(&tx_clk, rate);

Can you also check the return value of clk_set_rate() here?

Thanks,
Lukas

> +#endif
> +
>  	return 0;
>  }
>  #else