linux-kernel - Re: [PATCH net 2/3] net: dsa: mt7530: move lowering TRGMII driving to mt7530

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Date:   Sun, 26 Mar 2023 18:13:49 +0000
From:   Landen Chao (趙皎宏) 
        <Landen.Chao@...iatek.com>
To:     "olteanv@...il.com" <olteanv@...il.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "arinc9.unal@...il.com" <arinc9.unal@...il.com>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        Sean Wang <Sean.Wang@...iatek.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "dqfext@...il.com" <dqfext@...il.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "erkin.bozoglu@...ont.com" <erkin.bozoglu@...ont.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "arinc.unal@...nc9.com" <arinc.unal@...nc9.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH net 2/3] net: dsa: mt7530: move lowering TRGMII driving to
 mt7530_setup()

On Mon, 2023-03-20 at 22:05 +0300, arinc9.unal@...il.com wrote:
> 
> I asked this before, MT7530 DSA driver maintainers, please explain
> the code
> I mentioned on the second paragraph.
> 
> ---
> @@ -2207,6 +2198,15 @@ mt7530_setup(struct dsa_switch *ds)
> 
>         mt7530_pll_setup(priv);
> 
> +       /* Lower Tx driving for TRGMII path */
> +       for (i = 0; i < NUM_TRGMII_CTRL; i++)
> +               mt7530_write(priv, MT7530_TRGMII_TD_ODT(i),
> +                            TD_DM_DRVP(8) | TD_DM_DRVN(8));
> +
I guess you ask this part, and I try my best to recall what the
original author said years ago.
It is used to adjust the RX delay of port 6 to match the tx
signal of the link partner.
> +       for (i = 0; i < NUM_TRGMII_CTRL; i++)
> +               mt7530_rmw(priv, MT7530_TRGMII_RD(i),
> +                          RD_TAP_MASK, RD_TAP(16));
> +
> 
>