netdev - Re: [PATCH net-next 12/13] net: dsa: sja1105: expose the SGMII PCS as an mdio

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Message-ID: <20210525115007.ntp52e4vutybb7lq@skbuf>
Date:   Tue, 25 May 2021 11:50:08 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Florian Fainelli <f.fainelli@...il.com>
CC:     Vladimir Oltean <olteanv@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH net-next 12/13] net: dsa: sja1105: expose the SGMII PCS as
 an mdio_device

On Mon, May 24, 2021 at 07:35:29PM -0700, Florian Fainelli wrote:
> 
> 
> On 5/24/2021 4:22 PM, Vladimir Oltean wrote:
> > From: Vladimir Oltean <vladimir.oltean@....com>
> > 
> > The SJA1110 has up to 4 PCSes for SGMII/2500base-x, and they have a
> > different access procedure compared to the SJA1105. Since both have a
> > register layout reminiscent of clause 45, the chosen abstraction to hide
> > this difference away was to implement an internal MDIO bus for the PCS,
> > and to use a high-level set of procedures called sja1105_pcs_read and
> > sja1105_pcs_write.
> > 
> > Since we touch all PCS accessors again, now it is a good time to check
> > for error codes from the hardware access as well. We can't propagate the
> > errors very far due to phylink returning void for mac_config and
> > mac_link_up, but at least we print them to the console.
> > 
> > The SGMII PCS of the SJA1110 is not functional at this point, it needs a
> > different initialization sequence compared to SJA1105. That will be done
> > by the next patch.
> > 
> > Cc: Russell King <linux@...linux.org.uk>
> > Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> > ---
> 
> [snip]
> 
> > +
> > +int sja1110_pcs_mdio_read(struct mii_bus *bus, int phy, int reg)
> > +{
> > +	struct sja1105_mdio_private *mdio_priv = bus->priv;
> > +	struct sja1105_private *priv = mdio_priv->priv;
> > +	const struct sja1105_regs *regs = priv->info->regs;
> > +	int offset, bank;
> > +	u64 addr;
> > +	u32 tmp;
> > +	u16 mmd;
> > +	int rc;
> > +
> > +	if (!(reg & MII_ADDR_C45))
> > +		return -EINVAL;
> > +
> > +	/* This addressing scheme reserves register 0xff for the bank address
> > +	 * register, so that can never be addressed.
> > +	 */
> > +	if (WARN_ON(offset == 0xff))
> > +		return -ENODEV;
> 
> offset is not initialized here, did you mean to do this after it gets
> initialized? And likewise in sja1110_pcs_mdio_write()?

Yikes, you're right, I fiddled around too much with this and I left it
broken, it seems.