linux-kernel - Re: [PATCH net-next v6 5/9] net: dsa: microchip: ksz9477: Add Wake on Magic Packet support

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Date:   Thu, 19 Oct 2023 20:29:53 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>,
        Eric Dumazet <edumazet@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Arun Ramadoss <arun.ramadoss@...rochip.com>,
        Conor Dooley <conor+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, kernel@...gutronix.de,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        UNGLinuxDriver@...rochip.com,
        "Russell King (Oracle)" <linux@...linux.org.uk>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH net-next v6 5/9] net: dsa: microchip: ksz9477: Add Wake
 on Magic Packet support

On Thu, Oct 19, 2023 at 02:28:46PM +0200, Oleksij Rempel wrote:
> Introduce Wake on Magic Packet (WoL) functionality to the ksz9477
> driver.
> 
> Major changes include:
> 
> 1. Extending the `ksz9477_handle_wake_reason` function to identify Magic
>    Packet wake events alongside existing wake reasons.
> 
> 2. Updating the `ksz9477_get_wol` and `ksz9477_set_wol` functions to
>    handle WAKE_MAGIC alongside the existing WAKE_PHY option, and to
>    program the switch's MAC address register accordingly when Magic
>    Packet wake-up is enabled. This change will prevent WAKE_MAGIC
>    activation if the related port has a different MAC address compared
>    to a MAC address already used by HSR or an already active WAKE_MAGIC
>    on another port.
> 
> 3. Adding a restriction in `ksz_port_set_mac_address` to prevent MAC
>    address changes on ports with active Wake on Magic Packet, as the
>    switch's MAC address register is utilized for this feature.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> ---
>  drivers/net/dsa/microchip/ksz9477.c    | 60 ++++++++++++++++++++++++--
>  drivers/net/dsa/microchip/ksz_common.c | 15 +++++--
>  drivers/net/dsa/microchip/ksz_common.h |  3 ++
>  3 files changed, 71 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/dsa/microchip/ksz9477.c b/drivers/net/dsa/microchip/ksz9477.c
> index b9419d4b5e7b..bcc8863951ca 100644
> --- a/drivers/net/dsa/microchip/ksz9477.c
> +++ b/drivers/net/dsa/microchip/ksz9477.c
> @@ -81,7 +81,8 @@ static int ksz9477_handle_wake_reason(struct ksz_device *dev, int port)
>  	if (!pme_status)
>  		return 0;
>  
> -	dev_dbg(dev->dev, "Wake event on port %d due to: %s %s\n", port,
> +	dev_dbg(dev->dev, "Wake event on port %d due to: %s %s %s\n", port,
> +		pme_status & PME_WOL_MAGICPKT ? "\"Magic Packet\"" : "",
>  		pme_status & PME_WOL_LINKUP ? "\"Link Up\"" : "",
>  		pme_status & PME_WOL_ENERGY ? "\"Enery detect\"" : "");

Trivial: if you format the printf string as %s%s%s and the arguments as
"\"Magic Packet\" " : "", then the printed line won't have a trailing
space at the end.

>  
> @@ -109,10 +110,22 @@ void ksz9477_get_wol(struct ksz_device *dev, int port,
>  
>  	wol->supported = WAKE_PHY;
>  
> +	/* Check if at this moment we would be able to get the MAC address
> +	 * and use it for WAKE_MAGIC support. This result may change dynamically
> +	 * depending on configuration of other ports.
> +	 */
> +	ret = ksz_switch_macaddr_get(dev->ds, port, NULL);
> +	if (!ret) {
> +		wol->supported |= WAKE_MAGIC;
> +		ksz_switch_macaddr_put(dev->ds);

I don't get it, why do you release the reference on the MAC address as
soon as you successfully get it? Without a reference held, the
programmed address still lingers on, but the HSR offload code, on a
different port with a different MAC address, can change it and break WoL.

> +	}
> +
>  	ret = ksz_pread8(dev, port, REG_PORT_PME_CTRL, &pme_ctrl);
>  	if (ret)
>  		return;
>  
> +	if (pme_ctrl & PME_WOL_MAGICPKT)
> +		wol->wolopts |= WAKE_MAGIC;
>  	if (pme_ctrl & (PME_WOL_LINKUP | PME_WOL_ENERGY))
>  		wol->wolopts |= WAKE_PHY;
>  }