linux-kernel - Re: [PATCH net-next v7 09/10] net: phy: smsc: use phy_read_poll

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Date:   Mon, 1 Jun 2020 15:05:27 -0400
From:   Kevin Groeneveld <kgroeneveld@...il.com>
To:     Dejin Zheng <zhengdejin5@...il.com>
Cc:     andrew@...n.ch, f.fainelli@...il.com, hkallweit1@...il.com,
        linux@...linux.org.uk, David Miller <davem@...emloft.net>,
        corbet@....net, tglx@...utronix.de, gregkh@...uxfoundation.org,
        allison@...utok.net, mchehab+samsung@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v7 09/10] net: phy: smsc: use phy_read_poll_timeout()
 to simplify the code

Resent as plain text this time.  Sorry to those that got this twice.

On Mon, Mar 23, 2020 at 11:10 AM Dejin Zheng <zhengdejin5@...il.com> wrote:
>
> use phy_read_poll_timeout() to replace the poll codes for
> simplify lan87xx_read_status() function.
>
> Suggested-by: Andrew Lunn <andrew@...n.ch>
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> Signed-off-by: Dejin Zheng <zhengdejin5@...il.com>
> ---
> v6 -> v7:
>         - adapt to a newly added parameter sleep_before_read.
> v5 -> v6:
>         - no changed.
> v4 -> v5:
>         - add msleep before phy_read_poll_timeout() to keep the
>           code more similar
> v3 -> v4:
>         - add this patch by Andrew's suggestion. Thanks Andrew!
>
>  drivers/net/phy/smsc.c | 16 +++++-----------
>  1 file changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/phy/smsc.c b/drivers/net/phy/smsc.c
> index b73298250793..93da7d3d0954 100644
> --- a/drivers/net/phy/smsc.c
> +++ b/drivers/net/phy/smsc.c
> @@ -112,8 +112,6 @@ static int lan87xx_read_status(struct phy_device *phydev)
>         int err = genphy_read_status(phydev);
>
>         if (!phydev->link && priv->energy_enable) {
> -               int i;
> -
>                 /* Disable EDPD to wake up PHY */
>                 int rc = phy_read(phydev, MII_LAN83C185_CTRL_STATUS);
>                 if (rc < 0)
> @@ -125,15 +123,11 @@ static int lan87xx_read_status(struct phy_device *phydev)
>                         return rc;
>
>                 /* Wait max 640 ms to detect energy */
> -               for (i = 0; i < 64; i++) {
> -                       /* Sleep to allow link test pulses to be sent */
> -                       msleep(10);
> -                       rc = phy_read(phydev, MII_LAN83C185_CTRL_STATUS);
> -                       if (rc < 0)
> -                               return rc;
> -                       if (rc & MII_LAN83C185_ENERGYON)
> -                               break;
> -               }
> +               phy_read_poll_timeout(phydev, MII_LAN83C185_CTRL_STATUS, rc,
> +                                     rc & MII_LAN83C185_ENERGYON, 10000,
> +                                     640000, true);
> +               if (rc < 0)
> +                       return rc;
>
>                 /* Re-enable EDPD */
>                 rc = phy_read(phydev, MII_LAN83C185_CTRL_STATUS);
> --
> 2.25.0

This patch causes the kernel log to be spammed with the following when
Ethernet cable is not connected:
SMSC LAN8710/LAN8720 2188000.ethernet-1:00: lan87xx_read_status failed: -110

It still seems to work but I think that is only a fluke.

The "if (rc < 0)" is not actually checking the return value of
phy_read_poll_timeout but is looking at the value of the register
read.  I don't think rc will ever be negative in this case.  If you
change the code to "rc = phy_read_poll_timeout(...)" so that it
actually checks the error then the function will behave differently
than before.  The original code would only return an error if phy_read
returned an error.  On a timeout it just continued.  So the "if" could
be changed to "if (rc < 0 && rc != -ETIMEDOUT)".  But you will still
get the extra messages in the log that were not there before.

Kevin