[U-Boot] [PATCH] cmd: mdio: Fix access to arbitrary PHY addresses

[Alex Marginean]

On 5/30/2019 3:08 AM, Vladimir Oltean wrote:
> Alex reported the following:
> 
>    "
>    I'm doing some MDIO work on a freescale/NXP platform and I bumped into
>    errors with this command:
>    => mdio r emdio#3 5 3
>    Reading from bus emdio#3
>    "Synchronous Abort" handler, esr 0x8600000e
>    elr: ffffffff862b8000 lr : 000000008200cce4 (reloc)
>    ...
> 
>    mdio list does not list any PHYs currently because ethernet is using DM
>    and the interfaces are not probed at this time.  The PHY does exist
>    on the bus though.
>    The above scenario works with this commit reverted:
>    e55047ec51a662c12ed53ff543ec7cdf158b2137 cmd: mdio: Switch to generic
>    helpers when accessing the registers
> 
>    The current code using generic helpers only works for PHYs that have
>    been registered and show up in bus->phymap and crashes for arbitrary
>    IDs.  I find it useful to allow reading from other addresses over MDIO
>    too, certainly helpful for people debugging MDIO on various boards.
>    "
> 
> Fix this by reverting to use the raw MDIO bus operations in case there
> is no PHY probed based on DT at the specified address.
> 
> This restores the old behavior for these PHYs, which means that the
> newly introduced MMD-over-C22 helpers won't be available for them, but
> at least they will be accessible again without crashing the system.
> 
> Fixes: e55047ec51a6 ("cmd: mdio: Switch to generic helpers when accessing the registers")
> Reported-by: Alex Marginean <alexm.osslist at gmail.com>
> Signed-off-by: Vladimir Oltean <olteanv at gmail.com>
> ---
>   cmd/mdio.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/cmd/mdio.c b/cmd/mdio.c
> index efe8c9ef0954..5e219f699d8d 100644
> --- a/cmd/mdio.c
> +++ b/cmd/mdio.c
> @@ -54,7 +54,10 @@ static int mdio_write_ranges(struct mii_dev *bus,
>   
>   		for (devad = devadlo; devad <= devadhi; devad++) {
>   			for (reg = reglo; reg <= reghi; reg++) {
> -				if (!extended)
> +				if (!phydev)
> +					err = bus->write(bus, addr, devad,
> +							 reg, data);
> +				else if (!extended)
>   					err = phy_write_mmd(phydev, devad,
>   							    reg, data);
>   				else
> @@ -88,7 +91,9 @@ static int mdio_read_ranges(struct mii_dev *bus,
>   			for (reg = reglo; reg <= reghi; reg++) {
>   				int val;
>   
> -				if (!extended)
> +				if (!phydev)
> +					val = bus->read(bus, addr, devad, reg);
> +				else if (!extended)
>   					val = phy_read_mmd(phydev, devad, reg);
>   				else
>   					val = phydev->drv->readext(phydev, addr,
> 

Reviewed-by: Alex Marginean <alexm.osslist at gmail.com>

Thanks!
Alex