linux-kernel - Re: [PATCH 9/9] net: dsa: mt7530: use external PCS driver

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Date:   Sat, 4 Feb 2023 15:02:00 +0000
From:   Daniel Golle <daniel@...rotopia.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     netdev@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Russell King <linux@...linux.org.uk>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        John Crispin <john@...ozen.org>, Felix Fietkau <nbd@....name>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        DENG Qingfang <dqfext@...il.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Jianhui Zhao <zhaojh329@...il.com>,
        Bjørn Mork <bjorn@...k.no>
Subject: Re: [PATCH 9/9] net: dsa: mt7530: use external PCS driver

Hi Vladimir,

thank you for the review!

On Sat, Feb 04, 2023 at 12:19:15AM +0200, Vladimir Oltean wrote:
> On Fri, Feb 03, 2023 at 07:06:53AM +0000, Daniel Golle wrote:
> > @@ -2728,11 +2612,14 @@ mt753x_phylink_mac_select_pcs(struct dsa_switch *ds, int port,
> >  
> >  	switch (interface) {
> >  	case PHY_INTERFACE_MODE_TRGMII:
> > +		return &priv->pcs[port].pcs;
> >  	case PHY_INTERFACE_MODE_SGMII:
> >  	case PHY_INTERFACE_MODE_1000BASEX:
> >  	case PHY_INTERFACE_MODE_2500BASEX:
> > -		return &priv->pcs[port].pcs;
> > +		if (!mt753x_is_mac_port(port))
> > +			return ERR_PTR(-EINVAL);
> 
> What is the reason for returning ERR_PTR(-EINVAL) to mac_select_pcs()?

The SerDes PCS units are only available for port 5 and 6. The code
should make sure that the corresponding interface modes are only used
on these two ports, so a BUG_ON(!mt753x_is_mac_port(port)) would also
do the trick, I guess. However, as dsa_port_phylink_mac_select_pcs may
also return ERR_PTR(-EOPNOTSUPP), returning ERR_PTR(-EINVAL) felt like
the right thing to do in that case.
Are you suggesting to use BUG_ON() instead or rather return
ERR_PTR(-EOPNOTSUPP)?


> 
> >  
> > +		return priv->sgmii_pcs[port - 5];
> 
> How about putting the pcs pointer in struct mt7530_port?

There are only two SerDes units available, only for port 5 and port 6.
Hence I wouldn't want to allocate additional unused sizeof(void*) for
ports 0 to 4.

> 
> >  	default:
> >  		return NULL;
> >  	}
> > @@ -3088,8 +2934,6 @@ mt753x_setup(struct dsa_switch *ds)
> >  		priv->pcs[i].pcs.ops = priv->info->pcs_ops;
> >  		priv->pcs[i].priv = priv;
> >  		priv->pcs[i].port = i;
> > -		if (mt753x_is_mac_port(i))
> > -			priv->pcs[i].pcs.poll = 1;
> >  	}
> >  
> >  	ret = priv->info->sw_setup(ds);
> > @@ -3104,6 +2948,15 @@ mt753x_setup(struct dsa_switch *ds)
> >  	if (ret && priv->irq)
> >  		mt7530_free_irq_common(priv);
> 
> You need to patch the previous code to "return ret".
> 
> >  
> > +	if (priv->id == ID_MT7531)
> 
> if the code block below is multi-line (which it is), put braces here too
> 
> or can return early if priv->id != ID_MT7531, and this reduces the
> indentation by one level.
> 
> > +		for (i = 0; i < 2; ++i) {
> 
> could also iterate over all ports and ignore those which have
> !mt753x_is_mac_port(port)
> 
> > +			regmap = devm_regmap_init(ds->dev,
> > +						  &mt7531_regmap_bus, priv,
> > +						  &mt7531_pcs_config[i]);
> 
> can fail
> 
> > +			priv->sgmii_pcs[i] = mtk_pcs_create(ds->dev, regmap,
> > +							    0x128, 0);
> 
> can fail
> 
> Don't forget to do error teardown which isn't leaky
> 
> 0x128 comes from the old definition of MT7531_PHYA_CTRL_SIGNAL3(port),
> so please keep a macro of some sorts to denote the offset of ana_rgc3
> for MT7531, rather than just this obscure magic number.
> 
> > +		}
> > +
> >  	return ret;
> >  }
> >  
> > @@ -3199,7 +3052,7 @@ static const struct mt753x_info mt753x_table[] = {
> >  	},
> >  	[ID_MT7531] = {
> >  		.id = ID_MT7531,
> > -		.pcs_ops = &mt7531_pcs_ops,
> > +		.pcs_ops = &mt7530_pcs_ops,
> >  		.sw_setup = mt7531_setup,
> >  		.phy_read_c22 = mt7531_ind_c22_phy_read,
> >  		.phy_write_c22 = mt7531_ind_c22_phy_write,
> > @@ -3309,7 +3162,7 @@ static void
> >  mt7530_remove(struct mdio_device *mdiodev)
> >  {
> >  	struct mt7530_priv *priv = dev_get_drvdata(&mdiodev->dev);
> > -	int ret = 0;
> > +	int ret = 0, i;
> >  
> >  	if (!priv)
> >  		return;
> > @@ -3328,6 +3181,11 @@ mt7530_remove(struct mdio_device *mdiodev)
> >  		mt7530_free_irq(priv);
> >  
> >  	dsa_unregister_switch(priv->ds);
> > +
> > +	for (i = 0; i < 2; ++i)
> 
> There is no ++i in this driver and there are 11 i++, so please be
> consistent with what exists.

As most likely in all cases a pre-increment is sufficient and less
resource consuming than a post-increment operation we should consider
switching them all to ++i instead of i++.
I will anyway use i++ in v2 for now.

> 
> > +		if (priv->sgmii_pcs[i])
> > +			mtk_pcs_destroy(priv->sgmii_pcs[i]);
> > +
> >  	mutex_destroy(&priv->reg_mutex);
> >  }
> >