linux-kernel - Re: [PATCH v5 10/10] net: stmmac: dwmac-sun8i: Handle integrated/external MDIOs

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Date:   Fri, 8 Sep 2017 15:26:32 +0200
From:   Corentin Labbe <clabbe.montjoie@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     robh+dt@...nel.org, mark.rutland@....com,
        maxime.ripard@...e-electrons.com, wens@...e.org,
        linux@...linux.org.uk, catalin.marinas@....com,
        will.deacon@....com, peppe.cavallaro@...com,
        alexandre.torgue@...com, f.fainelli@...il.com,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 10/10] net: stmmac: dwmac-sun8i: Handle
 integrated/external MDIOs

On Fri, Sep 08, 2017 at 03:05:20PM +0200, Andrew Lunn wrote:
> > +#define DWMAC_sUN8I_MDIO_MUX_INTERNAL_ID	0
> > +#define DWMAC_sUN8I_MDIO_MUX_EXTERNAL_ID	1
> >  
> >  /* H3/A64 specific bits */
> >  #define SYSCON_RMII_EN		BIT(13) /* 1: enable RMII (overrides EPIT) */
> > @@ -634,6 +639,76 @@ static int sun8i_dwmac_reset(struct stmmac_priv *priv)
> >  	return 0;
> >  }
> >  
> > +/* MDIO multiplexing switch function
> > + * This function is called by the mdio-mux layer when it thinks the mdio bus
> > + * multiplexer needs to switch.
> > + * 'current_child' is the current value of the mux register
> > + * 'desired_child' is the value of the 'reg' property of the target child MDIO
> > + * node.
> > + * The first time this function is called, current_child == -1.
> > + * If current_child == desired_child, then the mux is already set to the
> > + * correct bus.
> > + *
> > + * Note that we do not use reg/mask like mdio-mux-mmioreg because we need to
> > + * know easily which bus is used (reset must be done only for desired bus).
> > + */
> > +static int mdio_mux_syscon_switch_fn(int current_child, int desired_child,
> > +				     void *data)
> > +{
> > +	struct stmmac_priv *priv = data;
> > +	struct sunxi_priv_data *gmac = priv->plat->bsp_priv;
> > +	u32 reg, val;
> > +	int ret = 0;
> > +	bool need_reset = false;
> > +
> > +	if (current_child ^ desired_child) {
> > +		regmap_read(gmac->regmap, SYSCON_EMAC_REG, &reg);
> > +		switch (desired_child) {
> > +		case DWMAC_sUN8I_MDIO_MUX_INTERNAL_ID:
> > +			dev_info(priv->device, "Switch mux to internal PHY");
> > +			val = (reg & ~H3_EPHY_MUX_MASK) | H3_EPHY_SELECT;
> > +			if (gmac->use_internal_phy)
> > +				need_reset = true;
> > +			break;
> 
> This i don't get. Why do you need use_internal_phy? Isn't that
> implicit from DWMAC_sUN8I_MDIO_MUX_INTERNAL_ID? Is it even possible to
> use an external PHY on the internal MDIO bus?
> 

On my H3 box with external PHY, the MDIO mux library first select (for scan ?) the internal MDIO.
Without use_internal_phy usage, this board will launch a reset to use the internal MDIO... and this reset timeout/fail.
After the MDIO mux select the external MDIO.

> > +		case DWMAC_sUN8I_MDIO_MUX_EXTERNAL_ID:
> > +			dev_info(priv->device, "Switch mux to external PHY");
> > +			val = (reg & ~H3_EPHY_MUX_MASK) | H3_EPHY_SHUTDOWN;
> > +			if (!gmac->use_internal_phy)
> > +				need_reset = true;
> > +			break;
> 
> And is it possible to use the internal PHY on the external bus?
> 

I need to check that.

Regards