linux-kernel - Re: [RFC PATCH net-next v2 2/2] net: dsa: mt7530: introduce MMIO driver for MT7988 SoC

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Message-ID: <8494e02c-6c04-46c9-af86-a414f27fcf23@lunn.ch>
Date:   Wed, 29 Mar 2023 00:45:37 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Daniel Golle <daniel@...rotopia.org>
Cc:     netdev@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Sam Shih <Sam.Shih@...iatek.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        John Crispin <john@...ozen.org>, Felix Fietkau <nbd@....name>
Subject: Re: [RFC PATCH net-next v2 2/2] net: dsa: mt7530: introduce MMIO
 driver for MT7988 SoC

> @@ -146,11 +149,13 @@ core_write(struct mt7530_priv *priv, u32 reg, u32 val)
>  {
>  	struct mii_bus *bus = priv->bus;
>  
> -	mutex_lock_nested(&bus->mdio_lock, MDIO_MUTEX_NESTED);
> +	if (bus)
> +		mutex_lock_nested(&bus->mdio_lock, MDIO_MUTEX_NESTED);
>  
>  	core_write_mmd_indirect(priv, reg, MDIO_MMD_VEND2, val);
>  
> -	mutex_unlock(&bus->mdio_lock);
> +	if (bus)
> +		mutex_unlock(&bus->mdio_lock);
>  }

All this if (bus) is pretty ugly.

First off, what is this mutex actually protecting? And why is the same
protection not required for MMIO?

If you have a convincing argument the mutex is not needed, please add
two helpers:

mt7530_mutex_lock(struct mt7530_priv *priv)
mt7530_mutex_unlock(struct mt7530_priv *priv)

and hide the if inside that. As part of the commit message, explain
why the mutex is not needed for MDIO.

Adding these helpers and changing all calls can be a preparation
patch. It is the sort of patch which should be obviously correct.

> @@ -2588,6 +2664,8 @@ mt7531_mac_config(struct dsa_switch *ds, int port, unsigned int mode,
>  	case PHY_INTERFACE_MODE_NA:
>  	case PHY_INTERFACE_MODE_1000BASEX:
>  	case PHY_INTERFACE_MODE_2500BASEX:
> +	case PHY_INTERFACE_MODE_USXGMII:
> +	case PHY_INTERFACE_MODE_10GKR:
>  		/* handled in SGMII PCS driver */
>  		return 0;
>  	default:
> @@ -2712,7 +2790,9 @@ static void mt753x_phylink_mac_link_up(struct dsa_switch *ds, int port,
>  	 * variants.
>  	 */
>  	if (interface == PHY_INTERFACE_MODE_TRGMII ||
> -	    (phy_interface_mode_is_8023z(interface))) {
> +	    interface == PHY_INTERFACE_MODE_USXGMII ||
> +	    interface == PHY_INTERFACE_MODE_10GKR ||
> +	    phy_interface_mode_is_8023z(interface)) {
>  		speed = SPEED_1000;
>  		duplex = DUPLEX_FULL;
>  	}

This looks like something which should be in a separate patch.

> +static int mt7988_setup(struct dsa_switch *ds)
> +{
> +	struct mt7530_priv *priv = ds->priv;
> +	u32 unused_pm = 0;
> +	int i;
> +
> +	/* Reset the switch */
> +	reset_control_assert(priv->rstc);
> +	udelay(20);
> +	reset_control_deassert(priv->rstc);
> +	udelay(20);
> +
> +	/* Reset the switch PHYs */
> +	mt7530_write(priv, MT7530_SYS_CTRL, SYS_CTRL_PHY_RST);
> +
> +	/* BPDU to CPU port */
> +	mt7530_rmw(priv, MT7531_CFC, MT7531_CPU_PMAP_MASK,
> +		   BIT(MT7988_CPU_PORT));
> +	mt7530_rmw(priv, MT753X_BPC, MT753X_BPDU_PORT_FW_MASK,
> +		   MT753X_BPDU_CPU_ONLY);
> +
> +	/* Enable and reset MIB counters */
> +	mt7530_mib_reset(ds);
> +
> +	for (i = 0; i < MT7530_NUM_PORTS; i++) {
> +		/* Disable forwarding by default on all ports */
> +		mt7530_rmw(priv, MT7530_PCR_P(i), PCR_MATRIX_MASK,
> +			   PCR_MATRIX_CLR);
> +
> +		mt7530_set(priv, MT7531_DBG_CNT(i), MT7531_DIS_CLR);
> +
> +		if (dsa_is_unused_port(ds, i))
> +			unused_pm |= BIT(i);
> +		else if (dsa_is_cpu_port(ds, i))
> +			mt753x_cpu_port_enable(ds, i);
> +		else
> +			mt7530_port_disable(ds, i);
> +
> +		/* Enable consistent egress tag */
> +		mt7530_rmw(priv, MT7530_PVC_P(i), PVC_EG_TAG_MASK,
> +			   PVC_EG_TAG(MT7530_VLAN_EG_CONSISTENT));
> +	}
> +
> +	ds->configure_vlan_while_not_filtering = true;
> +
> +	/* Flush the FDB table */
> +	return mt7530_fdb_cmd(priv, MT7530_FDB_FLUSH, NULL);

Is this really specific to the mt7988? 

   Andrew