netdev - Re: [PATCH net-next 9/9] phy: fixed_phy: Set phy capabilities even when link is down

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Message-ID: <20150824163230.GB6781@lunn.ch>
Date:	Mon, 24 Aug 2015 18:32:30 +0200
From:	Andrew Lunn <andrew@...n.ch>
To:	Florian Fainelli <f.fainelli@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 9/9] phy: fixed_phy: Set phy capabilities even
 when link is down

On Sun, Aug 23, 2015 at 11:40:07AM -0700, Florian Fainelli wrote:
> Le 08/23/15 02:47, Andrew Lunn a écrit :
> > What features a phy supports is masked in genphy_config_init() by
> > looking at the PHYs BMSR register.
> > 
> > If the link is down, fixed_phy_update_regs() will only set the auto-
> > negotiation capable bit in BMSR. Thus genphy_config_init() comes to
> > the conclusion the PHY can only perform 10/Half, and masks out the
> > higher speed features. If however the link it up, BMSR is set to
> > indicate the speed the PHY is capable of auto-negotiating, and
> > genphy_config_init() does not mask out the high speed features.
> > 
> > To fix this, when the link is down, have fixed_phy_update_regs() leave
> > the link status and auto-negotiation complete bit unset, but set all
> > the other bits depending on the fixed phy speed.
> 
> This kinds of revert what Staas did in commit
> 868a4215be9a6d80548ccb74763b883dc99d32a2 ("net: phy: fixed_phy: handle
> link-down case"). When the link is down, it does not seem to me like we
> can rely on the previous speed and duplex parameters to be considered valid.
> 
> Your change does fix a valid use case though... humm.

Hi Florian

I took at look at Staas fix, and read a bit about what the different
bits mean. I've reworked the patch. I now always set the local phy
capabilities in BMSR, but only set the negotiated speed and link
partner capabilities if the link it up. I also don't error out on
speed=0, unless the link is up.

This works for my use case, and hopefully also Staas.

I will post the new version when we have come to a conclusion about
other open issues.

      Andrew
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