linux-kernel - Re: [PATCH net] net: phy: sfp: fix the BR,min computation

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Message-ID: <20180508120527.GI16141@n2100.armlinux.org.uk>
Date:   Tue, 8 May 2018 13:05:27 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Antoine Tenart <antoine.tenart@...tlin.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com,
        maxime.chevallier@...tlin.com, gregory.clement@...tlin.com,
        miquel.raynal@...tlin.com, nadavh@...vell.com, stefanc@...vell.com,
        ymarkman@...vell.com, mw@...ihalf.com
Subject: Re: [PATCH net] net: phy: sfp: fix the BR,min computation

On Fri, May 04, 2018 at 05:10:54PM +0200, Antoine Tenart wrote:
> In an SFP EEPROM values can be read to get information about a given SFP
> module. One of those is the bitrate, which can be determined using a
> nominal bitrate in addition with min and max values (in %). The SFP code
> currently compute both BR,min and BR,max values thanks to this nominal
> and min,max values.
> 
> This patch fixes the BR,min computation as the min value should be
> subtracted to the nominal one, not added.
> 
> Fixes: 9962acf7fb8c ("sfp: add support for 1000Base-PX and 1000Base-BX10")
> Signed-off-by: Antoine Tenart <antoine.tenart@...tlin.com>

I know David has already applied it, but for the record, your fix looks
correct, thanks.

> ---
>  drivers/net/phy/sfp-bus.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/phy/sfp-bus.c b/drivers/net/phy/sfp-bus.c
> index 0381da78d228..fd6c23f69c2f 100644
> --- a/drivers/net/phy/sfp-bus.c
> +++ b/drivers/net/phy/sfp-bus.c
> @@ -125,7 +125,7 @@ void sfp_parse_support(struct sfp_bus *bus, const struct sfp_eeprom_id *id,
>  	if (id->base.br_nominal) {
>  		if (id->base.br_nominal != 255) {
>  			br_nom = id->base.br_nominal * 100;
> -			br_min = br_nom + id->base.br_nominal * id->ext.br_min;
> +			br_min = br_nom - id->base.br_nominal * id->ext.br_min;
>  			br_max = br_nom + id->base.br_nominal * id->ext.br_max;
>  		} else if (id->ext.br_max) {
>  			br_nom = 250 * id->ext.br_max;
> -- 
> 2.17.0
> 

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