linux-kernel - Re: [PATCH net-next v2] net: phy: micrel: ksz9131 led errata workaround

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Message-ID: <71c35967a1a40557cc034ff7d716fec367d5b4a1.camel@toradex.com>
Date:   Thu, 7 Oct 2021 17:08:37 +0000
From:   Philippe Schenker <philippe.schenker@...adex.com>
To:     "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "kuba@...nel.org" <kuba@...nel.org>,
        Francesco Dolcini <francesco.dolcini@...adex.com>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "davem@...emloft.net" <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v2] net: phy: micrel: ksz9131 led errata
 workaround

On Thu, 2021-10-07 at 18:45 +0200, Francesco Dolcini wrote:
> Micrel KSZ9131 PHY LED behavior is not correct when configured in
> Individual Mode, LED1 (Activity LED) is in the ON state when there is
> no-link.
> 
> Workaround this by setting bit 9 of register 0x1e after verifying that
> the LED configuration is Individual Mode.
> 
> This issue is described in KSZ9131RNX Silicon Errata DS80000693B [*]
> and according to that it will not be corrected in a future silicon
> revision.
> 
> [*]
> https://ww1.microchip.com/downloads/en/DeviceDoc/KSZ9131RNX-Silicon-Errata-and-Data-Sheet-Clarification-80000863B.pdf
> 
> Signed-off-by: Francesco Dolcini <francesco.dolcini@...adex.com>

This patch looks good to me, functionality wise it will work. I would
still do some defines for the raw values you used that are described in
the datasheet and maybe change the strange defines I introduced some
while ago, but I don't see this as a blocker.

Reviewed-by: Philippe Schenker <philippe.schenker@...adex.com>

> ---
> Changes v1 => v2:
>  1. corrected errata URL in commit message
>  2. check phy_read_mmd return value
> ---
>  drivers/net/phy/micrel.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
> index c330a5a9f665..b70f62efdbc3 100644
> --- a/drivers/net/phy/micrel.c
> +++ b/drivers/net/phy/micrel.c
> @@ -1003,6 +1003,26 @@ static int ksz9131_config_rgmii_delay(struct
> phy_device *phydev)
>                               txcdll_val);
>  }
>  
> +/* Silicon Errata DS80000693B
> + *
> + * When LEDs are configured in Individual Mode, LED1 is ON in a no-
> link
> + * condition. Workaround is to set register 0x1e, bit 9, this way
> LED1 behaves
> + * according to the datasheet (off if there is no link).
> + */
> +static int ksz9131_led_errata(struct phy_device *phydev)
> +{
> +       int reg;
> +
> +       reg = phy_read_mmd(phydev, 2, 0);
> +       if (reg < 0)
> +               return reg;
> +
> +       if (!(reg & BIT(4)))
> +               return 0;
> +
> +       return phy_set_bits(phydev, 0x1e, BIT(9));
> +}
> +
>  static int ksz9131_config_init(struct phy_device *phydev)
>  {
>         struct device_node *of_node;
> @@ -1058,6 +1078,10 @@ static int ksz9131_config_init(struct
> phy_device *phydev)
>         if (ret < 0)
>                 return ret;
>  
> +       ret = ksz9131_led_errata(phydev);
> +       if (ret < 0)
> +               return ret;
> +
>         return 0;
>  }
>