netdev - Re: [PATCH v2 net 1/1] amd-xgbe: fix active cable

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Date:   Fri, 11 Nov 2022 08:18:00 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Thomas Kupper <thomas@...per.org>, netdev@...r.kernel.org
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Raju Rangoju <Raju.Rangoju@....com>
Subject: Re: [PATCH v2 net 1/1] amd-xgbe: fix active cable

On 11/11/22 02:46, Thomas Kupper wrote:
> When determine the type of SFP, active cables were not handled.
> 
> Add the check for active cables as an extension to the passive cable check.

Is this fixing a particular problem? What SFP is this failing for? A more 
descriptive commit message would be good.

Also, since an active cable is supposed to be advertising it's 
capabilities in the eeprom, maybe this gets fixed via a quirk and not a 
general check this field.

> 
> Fixes: abf0a1c2b26a ("amd-xgbe: Add support for SFP+ modules")
> Signed-off-by: Thomas Kupper <thomas.kupper@...il.com>
> ---
>   drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c 
> b/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
> index 4064c3e3dd49..1ba550d5c52d 100644
> --- a/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
> +++ b/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
> @@ -1158,8 +1158,9 @@ static void xgbe_phy_sfp_parse_eeprom(struct 
> xgbe_prv_data *pdata)
>       }
> 
>       /* Determine the type of SFP */
> -    if (phy_data->sfp_cable == XGBE_SFP_CABLE_PASSIVE &&
> -        xgbe_phy_sfp_bit_rate(sfp_eeprom, XGBE_SFP_SPEED_10000))
> +    if ((phy_data->sfp_cable == XGBE_SFP_CABLE_PASSIVE ||
> +         phy_data->sfp_cable == XGBE_SFP_CABLE_ACTIVE) &&
> +         xgbe_phy_sfp_bit_rate(sfp_eeprom, XGBE_SFP_SPEED_10000))

This is just the same as saying:

	if (xgbe_phy_sfp_bit_rate(sfp_eeprom, XGBE_SFP_SPEED_10000))

since the sfp_cable value is either PASSIVE or ACTIVE.

I'm not sure I like fixing whatever issue you have in this way, though. If 
anything, I would prefer this to be a last case scenario and be placed at 
the end of the if-then-else block. But it may come down to applying a 
quirk for your situation.

Thanks,
Tom

>           phy_data->sfp_base = XGBE_SFP_BASE_10000_CR;
>       else if (sfp_base[XGBE_SFP_BASE_10GBE_CC] & XGBE_SFP_BASE_10GBE_CC_SR)
>           phy_data->sfp_base = XGBE_SFP_BASE_10000_SR;
> -- 
> 2.34.1
>