linux-kernel - Re: [RFC PATCH 09/13] net: phy: Add Meson GXL Internal PHY driver

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Message-ID: <eb0b2cb7-6730-f74a-ca18-460dcb57697e@baylibre.com>
Date:   Mon, 31 Oct 2016 15:25:29 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Florian Fainelli <f.fainelli@...il.com>, khilman@...libre.com,
        carlo@...one.org, linus.walleij@...aro.org
Cc:     linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [RFC PATCH 09/13] net: phy: Add Meson GXL Internal PHY driver

On 10/21/2016 10:56 PM, Florian Fainelli wrote:
> On 10/21/2016 07:40 AM, Neil Armstrong wrote:
>> Add driver for the Internal RMII PHY found in the Amlogic Meson GXL SoCs.
>>
>> This PHY seems to only implement some standard registers and need some
>> workarounds to provide autoneg values from vendor registers.
>>
>> Some magic values are currently used to configure the PHY, and this a
>> temporary setup until clarification about these registers names and
>> registers fields are provided by Amlogic.
>>
>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
>> ---
>> +
>> +static int meson_gxl_config_init(struct phy_device *phydev)
>> +{
>> +	int val;
>> +	u32 features;
>> +
>> +	meson_gxl_phy_config(phydev);
>> +
>> +	features = SUPPORTED_MII;
> 
> This does not really belong in the PHY driver, and this is statically
> assigned, I would just drop this.
> 

Ok

>> +
>> +	/* Do we support autonegotiation? */
>> +	val = phy_read(phydev, MII_BMSR);
>> +	if (val < 0)
>> +		return val;
>> +
>> +	if (val & BMSR_ANEGCAPABLE)
>> +		features |= SUPPORTED_Autoneg;
>> +	if (val & BMSR_100FULL)
>> +		features |= SUPPORTED_100baseT_Full;
>> +	if (val & BMSR_100HALF)
>> +		features |= SUPPORTED_100baseT_Half;
>> +	if (val & BMSR_10FULL)
>> +		features |= SUPPORTED_10baseT_Full;
>> +	if (val & BMSR_10HALF)
>> +		features |= SUPPORTED_10baseT_Half;
>> +
>> +	phydev->supported = features;
>> +	phydev->advertising = features;
> 
> This is redundant with what PHYLIB will determine for the PHY.
> 
ok

>> +
>> +	return 0;
>> +}
>> +
>> +static int meson_gxl_phy_read_status(struct phy_device *phydev)
>> +{
>> +	int err;
>> +
>> +	/* Update the link, but return if there was an error */
>> +	err = genphy_update_link(phydev);
>> +	if (err)
>> +		return err;
>> +
>> +	phydev->lp_advertising = 0;
>> +	phydev->pause = 0;
>> +	phydev->asym_pause = 0;
>> +
>> +	if (phydev->autoneg == AUTONEG_ENABLE) {
>> +		unsigned int speed;
>> +		int reg = phy_read(phydev, GXL_REG_ANEG);
> 
> Is all of this really necessary? This should all be reflected in the
> standard BMSR register, is not this the case here that we have to read
> this non-standard register?
> 

This is what I understood from the original driver code, but I will make some further tests
and see if the BMSR returns some good data.

> You use genphy_config_aneg(), so surely, the standard auto-negotiation
> part works somehow?

Yes, and the BMSR is also used in the config_init here...

> 
>> +
>> +		if (reg < 0)
>> +			return reg;
>> +
>> +		speed = reg & REG_ANEG_SPEED_MASK;
>> +
>> +		if (reg & REG_ANEG_FDUPLEX)
>> +			phydev->duplex = DUPLEX_FULL;
>> +		else
>> +			phydev->duplex = DUPLEX_HALF;
>> +
>> +		if ((reg & REG_ANEG_SPEED_MASK) == REG_ANEG_SPEED10)
>> +			phydev->speed = SPEED_10;
>> +		else if ((reg & REG_ANEG_SPEED_MASK) == REG_ANEG_SPEED100)
>> +			phydev->speed = SPEED_100;
>> +	} else {
>> +		int bmcr = phy_read(phydev, MII_BMCR);
>> +
>> +		if (bmcr < 0)
>> +			return bmcr;
>> +
>> +		if (bmcr & BMCR_FULLDPLX)
>> +			phydev->duplex = DUPLEX_FULL;
>> +		else
>> +			phydev->duplex = DUPLEX_HALF;
>> +
>> +		if (bmcr & BMCR_SPEED1000)
>> +			phydev->speed = SPEED_1000;
>> +		else if (bmcr & BMCR_SPEED100)
>> +			phydev->speed = SPEED_100;
>> +		else
>> +			phydev->speed = SPEED_10;
>> +	}
> 
>> +
>> +	return 0;
>> +}
>> +
>> +static struct phy_driver meson_gxl_phy = {
>> +	.phy_id		= 0x01814400,
>> +	.name		= "Meson GXL Internal PHY",
>> +	.phy_id_mask	= 0x0fffffff,
> 
> Usually the last 4 bits are 0, since that's where the revision part is
> located.
> 

Fixed

>> +	.features	= 0,
> 
> You should set PHY_GBIT_FEATURES and set .flags to PHY_IS_INTERNAL since
> this is an internal PHY?
> 

Ok

Thanks,
Neil