linux-kernel - Re: [PATCH net-next v2 5/7] net: dsa: mt7530: Add the support of MT7531 switch

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Date:   Wed, 19 Aug 2020 17:44:08 +0800
From:   Landen Chao <landen.chao@...iatek.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "vivien.didelot@...oirfairelinux.com" 
        <vivien.didelot@...oirfairelinux.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Sean Wang <Sean.Wang@...iatek.com>,
        "opensource@...rst.com" <opensource@...rst.com>,
        "frank-w@...lic-files.de" <frank-w@...lic-files.de>,
        "dqfext@...il.com" <dqfext@...il.com>
Subject: Re: [PATCH net-next v2 5/7] net: dsa: mt7530: Add the support of
 MT7531 switch

On Wed, 2020-08-19 at 00:09 +0800, Andrew Lunn wrote:
> On Tue, Aug 18, 2020 at 03:14:10PM +0800, Landen Chao wrote:
> > Add new support for MT7531:
> > 
> > MT7531 is the next generation of MT7530. It is also a 7-ports switch with
> > 5 giga embedded phys, 2 cpu ports, and the same MAC logic of MT7530. Cpu
> > port 6 only supports SGMII interface. Cpu port 5 supports either RGMII
> > or SGMII in different HW sku. Due to SGMII interface support, pll, and
> > pad setting are different from MT7530. This patch adds different initial
> > setting, and SGMII phylink handlers of MT7531.
> > 
> > MT7531 SGMII interface can be configured in following mode:
> > - 'SGMII AN mode' with in-band negotiation capability
> >     which is compatible with PHY_INTERFACE_MODE_SGMII.
> > - 'SGMII force mode' without in-bnad negotiation
> 
> band
Sorry, I'll fix it.
> 
> >     which is compatible with 10B/8B encoding of
> >     PHY_INTERFACE_MODE_1000BASEX with fixed full-duplex and fixed pause.
> > - 2.5 times faster clocked 'SGMII force mode' without in-bnad negotiation
> 
> band
Sorry, I'll fix it.
> 
> > +static int mt7531_rgmii_setup(struct mt7530_priv *priv, u32 port,
> > +			      phy_interface_t interface)
> > +{
> > +	u32 val;
> > +
> > +	if (!mt7531_is_rgmii_port(priv, port)) {
> > +		dev_err(priv->dev, "RGMII mode is not available for port %d\n",
> > +			port);
> > +		return -EINVAL;
> > +	}
> > +
> > +	val = mt7530_read(priv, MT7531_CLKGEN_CTRL);
> > +	val |= GP_CLK_EN;
> > +	val &= ~GP_MODE_MASK;
> > +	val |= GP_MODE(MT7531_GP_MODE_RGMII);
> > +	val &= ~(TXCLK_NO_REVERSE | RXCLK_NO_DELAY);
> > +	switch (interface) {
> > +	case PHY_INTERFACE_MODE_RGMII:
> > +		val |= TXCLK_NO_REVERSE;
> > +		val |= RXCLK_NO_DELAY;
> > +		break;
> > +	case PHY_INTERFACE_MODE_RGMII_RXID:
> > +		val |= TXCLK_NO_REVERSE;
> > +		break;
> > +	case PHY_INTERFACE_MODE_RGMII_TXID:
> > +		val |= RXCLK_NO_DELAY;
> > +		break;
> > +	case PHY_INTERFACE_MODE_RGMII_ID:
> > +		break;
> > +	default:
> > +		return -EINVAL;
> > +	}
> 
> You need to be careful here. If the MAC is doing the RGMII delays, you
> need to ensure the PHY is not. What interface mode is passed to the
> PHY?
Hi Andrew,

mt7531 RGMII port is a MAC-only port, it can be connected to CPU MAC or
external phy. In bpi-r64 board, mt7531 RGMII is connected to CPU MAC, so
I tend to implement RGMII logic for use case of bpi-r64.

In general, according to phy.rst, RGMII delay should be done by phy, but
some MoCA product need RGMII delay in MAC. These two requirements
conflict. Is there any suggestion to solve the conflict?

If mt7531 RGMII implementation needs to satisfy either phy.rst or
special MoCA product, I would like to satisfy phy.rst and remove MAC
RGMII delay in v3. For special product needs MAC RGMII delay, this patch
can be used in its local codebase.

Landen
> 
> 	Andrew