linux-kernel - Re: [PATCH] DSA support for Micrel KSZ8895

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Date:   Mon, 28 Aug 2017 09:02:32 +0200
From:   Pavel Machek <pavel@....cz>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Woojung.Huh@...rochip.com, nathan.leigh.conrad@...il.com,
        vivien.didelot@...oirfairelinux.com, f.fainelli@...il.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tristram.Ha@...rel.com
Subject: Re: [PATCH] DSA support for Micrel KSZ8895

Hi!

Thanks for review.

> > +	case PHY_REG_STATUS:
> > +		ksz_pread8(sw, p, P_LINK_STATUS, &link);
> > +		ksz_pread8(sw, p, P_SPEED_STATUS, &speed);
> > +		data = PHY_100BTX_FD_CAPABLE |
> > +			PHY_100BTX_CAPABLE |
> > +			PHY_10BT_FD_CAPABLE |
> > +			PHY_10BT_CAPABLE |
> > +			PHY_AUTO_NEG_CAPABLE;
> > +		if (link & PORT_AUTO_NEG_COMPLETE)
> > +			data |= PHY_AUTO_NEG_ACKNOWLEDGE;
> > +		if (link & PORT_STAT_LINK_GOOD)
> > +			data |= PHY_LINK_STATUS;
> > +		break;
> > +	case PHY_REG_ID_1:
> > +		data = KSZ8895_ID_HI;
> > +		break;
> > +	case PHY_REG_ID_2:
> > +		data = KSZ8895_ID_LO;
> > +		break;
> 
> According to the datasheet, the PHY has the normal ID registers,
> which have the value 0x0022, 0x1450. So it should be possible to have
> a standard PHY driver in drivers/net/phy.
> 
> In fact, the IDs suggest it is a micrel phy, and 1430, 1435 are
> already supported. So it could be you only need minor modifications to
> the micrel.c.

I may be confused here, but AFAICT:

1) Yes, it has standard layout when accessed over MDIO. But then
there's no access to the bridging functionality, and MDIO access may
not be available. [I was told not to use it for this design, so I did
not].

2) drivers/net/phy/spi_ks8995.c can be trivially modified to work with
this chip.. but then you don't get the bridge functionality. (And I'm
not sure how it works / who translates layouts in this case.)

I'd like to get rid of this code, or use some existing code instead,
but I don't think it is possible while keeping the SPI accesss. Let me
know if I'm wrong.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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