netdev - Re: [net PATCH 1/1] net: phy: fix phy link up when limiting speed via device tree

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Message-ID: <558C5061.6090509@ti.com>
Date:	Fri, 26 Jun 2015 00:32:57 +0530
From:	Mugunthan V N <mugunthanvnm@...com>
To:	Florian Fainelli <f.fainelli@...il.com>
CC:	netdev <netdev@...r.kernel.org>, David Miller <davem@...emloft.net>
Subject: Re: [net PATCH 1/1] net: phy: fix phy link up when limiting speed
 via device tree

On Thursday 25 June 2015 11:01 PM, Florian Fainelli wrote:
> 2015-06-25 9:51 GMT-07:00 Mugunthan V N <mugunthanvnm@...com>:
>> > When limiting phy link speed using "max-speed" to 100mbps or less on a
>> > giga bit phy, phy never completes auto negotiation and phy state
>> > machine is held in PHY_AN. Fixing this issue by comparing the giga
>> > bit advertise though phydev->supported doesn't have it but phy has
>> > BMSR_ESTATEN set. So that auto negotiation is restarted as old and
>> > new advertise are different and link comes up fine.
> This looks valid, however, I am curious why this part of the code:
> 
>         oldadv = adv;
>         adv &= ~(ADVERTISE_ALL | ADVERTISE_100BASE4 | ADVERTISE_PAUSE_CAP |
>                  ADVERTISE_PAUSE_ASYM);
>         adv |= ethtool_adv_to_mii_adv_t(advertise);
> 
>         if (adv != oldadv) {
>                 err = phy_write(phydev, MII_ADVERTISE, adv);
> 
>                 if (err < 0)
>                         return err;
>                 changed = 1;
>         }
> 
> Is not flagging this as a change already?
> 

This can flag a change when the selected limit is 10mbps, if 100mbps is
selected, at this instant oldadv and adv are same so change is not
flagged here.

Regards
Mugunthan V N
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