netdev - RE: [PATCH net-next 5/8] net: dpaa2-mac: use resolved link config in mac_link

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Message-ID: <DB8PR04MB6828131F75AB5D9162138F6DE0EA0@DB8PR04MB6828.eurprd04.prod.outlook.com>
Date:   Wed, 26 Feb 2020 15:07:51 +0000
From:   Ioana Ciornei <ioana.ciornei@....com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
CC:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Felix Fietkau <nbd@....name>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Jakub Kicinski <kuba@...nel.org>,
        John Crispin <john@...ozen.org>,
        Jonathan Corbet <corbet@....net>,
        Jose Abreu <joabreu@...opsys.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Michal Simek <michal.simek@...inx.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Radhey Shyam Pandey <radhey.shyam.pandey@...inx.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>
Subject: RE: [PATCH net-next 5/8] net: dpaa2-mac: use resolved link config in
 mac_link_up()


> Subject: Re: [PATCH net-next 5/8] net: dpaa2-mac: use resolved link config in
> mac_link_up()
> 
> On Tue, Feb 25, 2020 at 04:36:32PM +0000, Ioana Ciornei wrote:
> > > Subject: [PATCH net-next 5/8] net: dpaa2-mac: use resolved link
> > > config in
> > > mac_link_up()
> > >
> > > Convert the DPAA2 ethernet driver to use the finalised link
> > > parameters in
> > > mac_link_up() rather than the parameters in mac_config(), which are
> > > more suited to the needs of the DPAA2 MC firmware than those
> > > available via mac_config().
> > >
> > > Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
> >
> > Tested-by: Ioana Ciornei <ioana.ciornei@....com>
> 
> Thanks.
> 
> > > +
> > > +		/* This is lossy; the firmware really should take the pause
> > > +		 * enablement status rather than pause/asym pause status.
> > > +		 */
> >
> > In what sense it's lossy? I cannot see how information can be lost by
> translating the rx/tx pause state to pause/asym.
> > If it's just about the unnecessary double translation, then I agree.. this could
> have been done in an easier manner.
> 
> If you're just translating rx/tx to pause/asym and then doing the reverse, then it
> isn't lossy, but if the firmware is resolving pause/asym according to the table in
> IEEE 802.3, then it will be lossy.

The firmware is just doing the reverse translation.

> 
> If the firmware doesn't interpret the bits, then why not do the sensible thing and
> just pass the enablement status rather than trying to confusingly encode it back
> to pause/asym?

I agree. It's unnecessary and confusing. I'll add this on the list of fixups to be made by the firmware team.

Ioana

> 
> --