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

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Date:   Wed, 6 Oct 2021 23:57:45 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Francesco Dolcini <francesco.dolcini@...adex.com>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        philippe.schenker@...adex.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: phy: micrel: ksz9131 led errata workaround

On Wed, Oct 06, 2021 at 09:37:55AM +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
> (http://ww1.microchip.com/downloads/en/DeviceDoc/80000863A.pdf) and
> according to that it will not be corrected in a future silicon revision.
> 
> Signed-off-by: Francesco Dolcini <francesco.dolcini@...adex.com>
> ---
>  drivers/net/phy/micrel.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
> index c330a5a9f665..661dedec84c4 100644
> --- a/drivers/net/phy/micrel.c
> +++ b/drivers/net/phy/micrel.c
> @@ -1003,6 +1003,23 @@ 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 ret = 0;
> +
> +	if (phy_read_mmd(phydev, 2, 0) & BIT(4))

It would be good to check the return code here. If there is an error,
you are going to set bit 9.

Otherwise this looks O.K.

	  Andrew