netdev - Re: [PATCH] net: stmmac: don't set tx delay in RGMII_ID and RGMII

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Date:   Fri, 3 Feb 2017 20:47:49 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        linux-amlogic@...ts.infradead.org
Subject: Re: [PATCH] net: stmmac: don't set tx delay in RGMII_ID and
 RGMII_TXID mode

On Wed, Feb 1, 2017 at 8:19 PM, Heiner Kallweit <hkallweit1@...il.com> wrote:
> As documented in Documentation/devicetree/bindings/net/ethernet.txt,
> in RGMII_ID and RGMII_TXID mode the MAC should not add a tx delay.
>
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com"

> ---
>  drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
> index 8840a360..96855559 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
> @@ -177,12 +177,19 @@ static int meson8b_init_prg_eth(struct meson8b_dwmac *dwmac)
>  {
>         int ret;
>         unsigned long clk_rate;
> -       u8 tx_dly_val;
> +       u8 tx_dly_val = 0;
>
>         switch (dwmac->phy_mode) {
>         case PHY_INTERFACE_MODE_RGMII:
> -       case PHY_INTERFACE_MODE_RGMII_ID:
>         case PHY_INTERFACE_MODE_RGMII_RXID:
> +               /* TX clock delay in ns = "8ns / 4 * tx_dly_val" (where
> +                * 8ns are exactly one cycle of the 125MHz RGMII TX clock):
> +                * 0ns = 0x0, 2ns = 0x1, 4ns = 0x2, 6ns = 0x3
> +                */
> +               tx_dly_val = dwmac->tx_delay_ns >> 1;
> +               /* fall through */
> +
> +       case PHY_INTERFACE_MODE_RGMII_ID:
>         case PHY_INTERFACE_MODE_RGMII_TXID:
>                 /* Generate a 25MHz clock for the PHY */
>                 clk_rate = 25 * 1000 * 1000;
> @@ -195,11 +202,6 @@ static int meson8b_init_prg_eth(struct meson8b_dwmac *dwmac)
>                 meson8b_dwmac_mask_bits(dwmac, PRG_ETH0,
>                                         PRG_ETH0_INVERTED_RMII_CLK, 0);
>
> -               /* TX clock delay in ns = "8ns / 4 * tx_dly_val" (where
> -                * 8ns are exactly one cycle of the 125MHz RGMII TX clock):
> -                * 0ns = 0x0, 2ns = 0x1, 4ns = 0x2, 6ns = 0x3
> -                */
> -               tx_dly_val = dwmac->tx_delay_ns >> 1;
>                 meson8b_dwmac_mask_bits(dwmac, PRG_ETH0, PRG_ETH0_TXDLY_MASK,
>                                         tx_dly_val << PRG_ETH0_TXDLY_SHIFT);
>                 break;
> --
> 2.11.0
>
Heiner, many thanks for this and your other patches!