linux-kernel - Re: [PATCH] net: phy: dp83867: perform soft reset and retain established link

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Message-ID: <YFsxaBj/AvPpo13W@lunn.ch>
Date:   Wed, 24 Mar 2021 13:32:40 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     praneeth@...com
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Geet Modi <geet.modi@...com>
Subject: Re: [PATCH] net: phy: dp83867: perform soft reset and retain
 established link

On Tue, Mar 23, 2021 at 08:00:06PM -0500, praneeth@...com wrote:
> From: Praneeth Bajjuri <praneeth@...com>
> 
> Current logic is performing hard reset and causing the programmed
> registers to be wiped out.
> 
> as per datasheet: https://www.ti.com/lit/ds/symlink/dp83867cr.pdf
> 8.6.26 Control Register (CTRL)
> do SW_RESTART to perform a reset not including the registers and is
> acceptable to do this if a link is already present.

I don't see any code here to determine if the like is present. What if
the cable is not plugged in?

> @@ -826,7 +826,7 @@ static int dp83867_phy_reset(struct phy_device *phydev)
>  {
>  	int err;
>  
> -	err = phy_write(phydev, DP83867_CTRL, DP83867_SW_RESET);
> +	err = phy_write(phydev, DP83867_CTRL, DP83867_SW_RESTART);
>  	if (err < 0)
>  		return err;

The code continues

       usleep_range(10, 20);

        /* After reset FORCE_LINK_GOOD bit is set. Although the
         * default value should be unset. Disable FORCE_LINK_GOOD
         * for the phy to work properly.
         */
        return phy_modify(phydev, MII_DP83867_PHYCTRL,
                         DP83867_PHYCR_FORCE_LINK_GOOD, 0);
}

Do you still need to clear the FORCE_LINK_GOOD bit after a restart?

   Andrew