linux-kernel - RE: [PATCH] net/phy: tune get_phy_c45

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Message-ID: <DM2PR03MB398164CA6A138741831BAE2F8E70@DM2PR03MB398.namprd03.prod.outlook.com>
Date:	Mon, 13 Apr 2015 06:59:52 +0000
From:	"Shengzhou.Liu@...escale.com" <Shengzhou.Liu@...escale.com>
To:	David Miller <davem@...emloft.net>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"f.fainelli@...il.com" <f.fainelli@...il.com>
Subject: RE: [PATCH] net/phy: tune get_phy_c45_ids to support more c45 phy



> -----Original Message-----
> From: David Miller [mailto:davem@...emloft.net]
> Sent: Monday, April 13, 2015 8:42 AM
> To: Liu Shengzhou-B36685
> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org;
> f.fainelli@...il.com
> Subject: Re: [PATCH] net/phy: tune get_phy_c45_ids to support more c45 phy
> 
> From: Shengzhou Liu <Shengzhou.Liu@...escale.com>
> Date: Fri, 10 Apr 2015 17:10:20 +0800
> 
> >  		if ((c45_ids->devices_in_package & 0x1fffffff) == 0x1fffffff) {
> > -			*phy_id = 0xffffffff;
> > -			return 0;
> > +			reg_addr = MII_ADDR_C45 | 0 << 16 | 6;
> > +			phy_reg = mdiobus_read(bus, addr, reg_addr);
> > +			if (phy_reg < 0)
> > +				return -EIO;
> 
> Why are you reading this same register again, and why are you doing it with
> the magic constant "6".  That's not '6', it's 'MDIO_DEVS2'.
> 
> The first loop executed here should have read from this address, and placed
> the value into the ->devices_in_package.
> 
> This looks really like a hack.  You're reading again the same registers, by
> hand, that the loop should already be reading properly.
> 
> Why not restructure the loop to actually probe naturally for the presence
> bits in a way that works on the chip you are trying to make work?
 
Some PHYs(e.g. Cortina CS4315/CS4340) have zero Devices In package,
If we first probe zero Devices In package by loop for(i = 0; i < num_ids && c45_ids->devices_in_package == 0; i++),
it will cause the probe fail on those C45 PHYs with non-zero Devices In package.
So we must first probe non-zero Devices In package in the loop, if the return value
of c45_ids->devices_in_package is 0x1fffffff, then try to probe zero Devices In package.
Yes, will use MDIO_DEVS1 and MDIO_DEVS2 instead of constant '6', '5' in next version.
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