[U-Boot] [PATCH] net: phy: do not read configuration register on reset

[Stefan Roese]

On 09.12.2015 20:21, Stefan Agner wrote:
> When doing a software reset, the reset flag should be written without
> other bits set. Writing the current state will lead to restoring the
> state of the PHY (e.g. Powerdown), which is not what is expected from
> a software reset.
> 
> Signed-off-by: Stefan Agner <stefan at agner.ch>
> ---
> This lead to the PHY staying powered down on a reboot when using a
> Micrel PHY and not using hardware reset...
> 
> It also aligns with the behavior of Linux:
> http://lxr.free-electrons.com/source/drivers/net/phy/phy_device.c#L1122
> 
> --
> Stefan
> 
>   drivers/net/phy/phy.c | 11 ++---------
>   1 file changed, 2 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
> index 51b5746..ef9f13b 100644
> --- a/drivers/net/phy/phy.c
> +++ b/drivers/net/phy/phy.c
> @@ -717,15 +717,7 @@ int phy_reset(struct phy_device *phydev)
>   	}
>   #endif
>   
> -	reg = phy_read(phydev, devad, MII_BMCR);
> -	if (reg < 0) {
> -		debug("PHY status read failed\n");
> -		return -1;
> -	}
> -
> -	reg |= BMCR_RESET;
> -
> -	if (phy_write(phydev, devad, MII_BMCR, reg) < 0) {
> +	if (phy_write(phydev, devad, MII_BMCR, BMCR_RESET) < 0) {
>   		debug("PHY reset failed\n");
>   		return -1;
>   	}
> @@ -738,6 +730,7 @@ int phy_reset(struct phy_device *phydev)
>   	 * auto-clearing).  This should happen within 0.5 seconds per the
>   	 * IEEE spec.
>   	 */
> +	reg = phy_read(phydev, devad, MII_BMCR);
>   	while ((reg & BMCR_RESET) && timeout--) {
>   		reg = phy_read(phydev, devad, MII_BMCR);

This breaks PHY link auto negotiation support on Marvell Armada
388 ClearFog for me. As with this patch, bit 12 (A/N enable) will
get cleared. And the link is not established correctly.

The problem here seems to be, that the Marvell PHY driver calls
phy_reset() again at the end of m88e1111s_config(). Resulting 
in the loss of the configuration of the MII_BMCR register. I'm
currently thinking if this patchbelow would be the correct fix
for this problem?

diff --git a/drivers/net/phy/marvell.c b/drivers/net/phy/marvell.c
index eab1558..8ede927 100644
--- a/drivers/net/phy/marvell.c
+++ b/drivers/net/phy/marvell.c
@@ -270,8 +270,7 @@ static int m88e1111s_config(struct phy_device *phydev)
                printf("%s: phy soft reset timeout\n", __func__);
 
        genphy_config_aneg(phydev);
-
-       phy_reset(phydev);
+       genphy_restart_aneg(phydev);


Thanks,
Stefan