Re: [PATCH V2 1/2] net: phy: micrel: Discern KSZ8051 and KSZ8795 PHYs

[Heiner Kallweit <hkallweit1@gmail.com>]

On 12.10.2019 22:58, Heiner Kallweit wrote:
> On 10.10.2019 21:46, Marek Vasut wrote:
>> The KSZ8051 PHY and the KSZ8794/KSZ8795/KSZ8765 switch share exactly the
>> same PHY ID. Since KSZ8051 is higher in the ksphy_driver[] list of PHYs
>> in the micrel PHY driver, it is used even with the KSZ87xx switch. This
>> is wrong, since the KSZ8051 configures registers of the PHY which are
>> not present on the simplified KSZ87xx switch PHYs and misconfigures
>> other registers of the KSZ87xx switch PHYs.
>>
>> Fortunatelly, it is possible to tell apart the KSZ8051 PHY from the
>> KSZ87xx switch by checking the Basic Status register Bit 0, which is
>> read-only and indicates presence of the Extended Capability Registers.
>> The KSZ8051 PHY has those registers while the KSZ87xx switch does not.
>>
>> This patch implements simple check for the presence of this bit for
>> both the KSZ8051 PHY and KSZ87xx switch, to let both use the correct
>> PHY driver instance.
>>
>> Signed-off-by: Marek Vasut <marex@denx.de>
>> Cc: Andrew Lunn <andrew@lunn.ch>
>> Cc: David S. Miller <davem@davemloft.net>
>> Cc: Florian Fainelli <f.fainelli@gmail.com>
>> Cc: George McCollister <george.mccollister@gmail.com>
>> Cc: Heiner Kallweit <hkallweit1@gmail.com>
>> Cc: Tristram Ha <Tristram.Ha@microchip.com>
>> Cc: Woojung Huh <woojung.huh@microchip.com>
>> ---
>> NOTE: It was also suggested to populate phydev->dev_flags to discern
>>       the PHY from the switch, this does not work for setups where
>>       the switch is used as a PHY without a DSA driver. Checking the
>>       BMSR Bit 0 for Extended Capability Register works for both DSA
>>       and non-DSA usecase.
>> V2: Move phy_id check into ksz8051_match_phy_device() and
>>     ksz8795_match_phy_device() and drop phy_id{,_mask} from the
>>     ksphy_driver[] list to avoid matching on other PHY IDs.
>> ---
>>  drivers/net/phy/micrel.c | 40 ++++++++++++++++++++++++++++++++++++----
>>  1 file changed, 36 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
>> index 2fea5541c35a..028a4a177790 100644
>> --- a/drivers/net/phy/micrel.c
>> +++ b/drivers/net/phy/micrel.c
>> @@ -341,6 +341,25 @@ static int ksz8041_config_aneg(struct phy_device *phydev)
>>  	return genphy_config_aneg(phydev);
>>  }
>>  
>> +static int ksz8051_match_phy_device(struct phy_device *phydev)
>> +{
>> +	int ret;
>> +
>> +	if ((phydev->phy_id & MICREL_PHY_ID_MASK) != PHY_ID_KSZ8051)
>> +		return 0;
>> +
>> +	ret = phy_read(phydev, MII_BMSR);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	/* KSZ8051 PHY and KSZ8794/KSZ8795/KSZ8765 switch share the same
>> +	 * exact PHY ID. However, they can be told apart by the extended
>> +	 * capability registers presence. The KSZ8051 PHY has them while
>> +	 * the switch does not.
>> +	 */
>> +	return ret & BMSR_ERCAP;
>> +}
>> +
>>  static int ksz8081_config_init(struct phy_device *phydev)
>>  {
>>  	/* KSZPHY_OMSO_FACTORY_TEST is set at de-assertion of the reset line
>> @@ -364,6 +383,21 @@ static int ksz8061_config_init(struct phy_device *phydev)
>>  	return kszphy_config_init(phydev);
>>  }
>>  
>> +static int ksz8795_match_phy_device(struct phy_device *phydev)
>> +{
>> +	int ret;
>> +
>> +	if ((phydev->phy_id & MICREL_PHY_ID_MASK) != PHY_ID_KSZ8795)
>> +		return 0;
>> +
>> +	ret = phy_read(phydev, MII_BMSR);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	/* See comment in ksz8051_match_phy_device() for details. */
>> +	return !(ret & BMSR_ERCAP);
>> +}
>> +
>>  static int ksz9021_load_values_from_of(struct phy_device *phydev,
>>  				       const struct device_node *of_node,
>>  				       u16 reg,
>> @@ -1017,8 +1051,6 @@ static struct phy_driver ksphy_driver[] = {
>>  	.suspend	= genphy_suspend,
>>  	.resume		= genphy_resume,
>>  }, {
>> -	.phy_id		= PHY_ID_KSZ8051,
>> -	.phy_id_mask	= MICREL_PHY_ID_MASK,
>>  	.name		= "Micrel KSZ8051",
>>  	/* PHY_BASIC_FEATURES */
>>  	.driver_data	= &ksz8051_type,
>> @@ -1029,6 +1061,7 @@ static struct phy_driver ksphy_driver[] = {
>>  	.get_sset_count = kszphy_get_sset_count,
>>  	.get_strings	= kszphy_get_strings,
>>  	.get_stats	= kszphy_get_stats,
>> +	.match_phy_device = ksz8051_match_phy_device,
>>  	.suspend	= genphy_suspend,
>>  	.resume		= genphy_resume,
>>  }, {
>> @@ -1141,13 +1174,12 @@ static struct phy_driver ksphy_driver[] = {
>>  	.suspend	= genphy_suspend,
>>  	.resume		= genphy_resume,
>>  }, {
>> -	.phy_id		= PHY_ID_KSZ8795,
>> -	.phy_id_mask	= MICREL_PHY_ID_MASK,
>>  	.name		= "Micrel KSZ8795",
>>  	/* PHY_BASIC_FEATURES */
>>  	.config_init	= kszphy_config_init,
>>  	.config_aneg	= ksz8873mll_config_aneg,
>>  	.read_status	= ksz8873mll_read_status,
>> +	.match_phy_device = ksz8795_match_phy_device,
>>  	.suspend	= genphy_suspend,
>>  	.resume		= genphy_resume,
>>  }, {
>>
> 
> Patch needs to be annotated as "net-next".
> See https://www.kernel.org/doc/Documentation/networking/netdev-FAQ.txt
> 
Except you consider this a fix, then it would require a Fixes tag and
should be annotated "net". The question is:
Do KSZ87xx switches misbehave currently?

> Apart from that:
> Reviewed-by: Heiner Kallweit <hkallweit1@gmail.com>
>