netdev - Re: [PATCH net-next 4/7] net: dsa: felix: set proper pause frame timers based on link speed

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Date:   Thu, 25 Jun 2020 17:37:15 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, andrew@...n.ch,
        f.fainelli@...il.com, vivien.didelot@...il.com,
        claudiu.manoil@....com, alexandru.marginean@....com,
        ioana.ciornei@....com
Subject: Re: [PATCH net-next 4/7] net: dsa: felix: set proper pause frame
 timers based on link speed

On Thu, Jun 25, 2020 at 06:23:28PM +0300, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
> 
> state->speed holds a value of 10, 100, 1000 or 2500, but
> SYS_MAC_FC_CFG_FC_LINK_SPEED expects a value in the range 0, 1, 2 or 3.
> 
> So set the correct speed encoding into this register.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---
>  drivers/net/dsa/ocelot/felix.c | 27 +++++++++++++++++++++++----
>  1 file changed, 23 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/dsa/ocelot/felix.c b/drivers/net/dsa/ocelot/felix.c
> index d229cb5d5f9e..da337c63e7ca 100644
> --- a/drivers/net/dsa/ocelot/felix.c
> +++ b/drivers/net/dsa/ocelot/felix.c
> @@ -250,10 +250,25 @@ static void felix_phylink_mac_config(struct dsa_switch *ds, int port,
>  			   DEV_CLOCK_CFG_LINK_SPEED(OCELOT_SPEED_1000),
>  			   DEV_CLOCK_CFG);
>  
> -	/* Flow control. Link speed is only used here to evaluate the time
> -	 * specification in incoming pause frames.
> -	 */
> -	mac_fc_cfg = SYS_MAC_FC_CFG_FC_LINK_SPEED(state->speed);
> +	switch (state->speed) {
> +	case SPEED_10:
> +		mac_fc_cfg = SYS_MAC_FC_CFG_FC_LINK_SPEED(3);
> +		break;
> +	case SPEED_100:
> +		mac_fc_cfg = SYS_MAC_FC_CFG_FC_LINK_SPEED(2);
> +		break;
> +	case SPEED_1000:
> +	case SPEED_2500:
> +		mac_fc_cfg = SYS_MAC_FC_CFG_FC_LINK_SPEED(1);
> +		break;
> +	case SPEED_UNKNOWN:
> +		mac_fc_cfg = SYS_MAC_FC_CFG_FC_LINK_SPEED(0);
> +		break;
> +	default:
> +		dev_err(ocelot->dev, "Unsupported speed on port %d: %d\n",
> +			port, state->speed);
> +		return;
> +	}
>  
>  	/* handle Rx pause in all cases, with 2500base-X this is used for rate
>  	 * adaptation.
> @@ -265,6 +280,10 @@ static void felix_phylink_mac_config(struct dsa_switch *ds, int port,
>  			      SYS_MAC_FC_CFG_PAUSE_VAL_CFG(0xffff) |
>  			      SYS_MAC_FC_CFG_FC_LATENCY_CFG(0x7) |
>  			      SYS_MAC_FC_CFG_ZERO_PAUSE_ENA;
> +
> +	/* Flow control. Link speed is only used here to evaluate the time
> +	 * specification in incoming pause frames.
> +	 */
>  	ocelot_write_rix(ocelot, mac_fc_cfg, SYS_MAC_FC_CFG, port);

I'm not that happy with the persistence of felix using the legacy
method; I can bring a horse to water but can't make it drink comes
to mind.  I'm at the point where I don't care _if_ my phylink changes
break code that I've asked people to convert and they haven't yet,
and I'm planning to send the series that /may/ cause breakage in
that regard pretty soon, so the lynx PCS changes can move forward.

I even tried to move felix forward by sending a patch for it, and I
just gave up with that approach based on your comment.

Shrug.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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