Re: [PATCH V3 1/2] net: phy: micrel: Discern KSZ8051 and KSZ8795 PHYs

[Heiner Kallweit <hkallweit1@gmail.com>]

On 13.10.2019 21:34, 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: Sean Nyekjaer <sean.nyekjaer@prevas.dk>
> Cc: Tristram Ha <Tristram.Ha@microchip.com>
> Cc: Woojung Huh <woojung.huh@microchip.com>
> Fixes: 9d162ed69f51 ("net: phy: micrel: add support for KSZ8795")

The Fixes tag has to be the first one. And patch still misses
the "net" annotation. For an example just see other fix submissions
on the mailing list.

> ---
> 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.
> V3: Pull the logic behind discerning the KSZ8051 PHY and KSZ87xx switch
>     into common ksz8051_ksz8795_match_phy_device() function. Add Fixes
>     tag.
> ---
>  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..a0444e28c6e7 100644
> --- a/drivers/net/phy/micrel.c
> +++ b/drivers/net/phy/micrel.c
> @@ -341,6 +341,35 @@ static int ksz8041_config_aneg(struct phy_device *phydev)
>  	return genphy_config_aneg(phydev);
>  }
>  
> +static int ksz8051_ksz8795_match_phy_device(struct phy_device *phydev,
> +					    const u32 ksz_phy_id)
> +{
> +	int ret;
> +
> +	if ((phydev->phy_id & MICREL_PHY_ID_MASK) != ksz_phy_id)
> +		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.
> +	 */
> +	ret &= BMSR_ERCAP;
> +	if (ksz_phy_id == PHY_ID_KSZ8051)
> +		return ret;
> +	else
> +		return !ret;
> +}
> +
> +static int ksz8051_match_phy_device(struct phy_device *phydev)
> +{
> +	return ksz8051_ksz8795_match_phy_device(phydev, PHY_ID_KSZ8051);
> +}
> +
>  static int ksz8081_config_init(struct phy_device *phydev)
>  {
>  	/* KSZPHY_OMSO_FACTORY_TEST is set at de-assertion of the reset line
> @@ -364,6 +393,11 @@ static int ksz8061_config_init(struct phy_device *phydev)
>  	return kszphy_config_init(phydev);
>  }
>  
> +static int ksz8795_match_phy_device(struct phy_device *phydev)
> +{
> +	return ksz8051_ksz8795_match_phy_device(phydev, PHY_ID_KSZ8795);
> +}
> +
>  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,
>  }, {
>