netdev - Re: [PATCH net-next v3 7/8] dpaa2-mac: configure the SerDes phy on a protocol change

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Date:   Thu, 10 Mar 2022 15:57:10 +0000
From:   Ioana Ciornei <ioana.ciornei@....com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kishon@...com" <kishon@...com>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        Leo Li <leoyang.li@....com>,
        "linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Hongxing Zhu <hongxing.zhu@....com>
Subject: Re: [PATCH net-next v3 7/8] dpaa2-mac: configure the SerDes phy on a
 protocol change

On Thu, Mar 10, 2022 at 03:05:50PM +0000, Russell King (Oracle) wrote:
> On Thu, Mar 10, 2022 at 04:51:59PM +0200, Ioana Ciornei wrote:
> > This patch integrates the dpaa2-eth driver with the generic PHY
> > infrastructure in order to search, find and reconfigure the SerDes lanes
> > in case of a protocol change.
> > 
> > On the .mac_config() callback, the phy_set_mode_ext() API is called so
> > that the Lynx 28G SerDes PHY driver can change the lane's configuration.
> > In the same phylink callback the MC firmware is called so that it
> > reconfigures the MAC side to run using the new protocol.
> > 
> > The consumer drivers - dpaa2-eth and dpaa2-switch - are updated to call
> > the dpaa2_mac_start/stop functions newly added which will
> > power_on/power_off the associated SerDes lane.
> > 
> > Signed-off-by: Ioana Ciornei <ioana.ciornei@....com>
> 
> Looks better, there's a minor thing that I missed, sorry:
> 
> > +	if (mac->features & DPAA2_MAC_FEATURE_PROTOCOL_CHANGE &&
> > +	    !phy_interface_mode_is_rgmii(mac->if_mode) &&
> > +	    is_of_node(dpmac_node)) {
> > +		serdes_phy = of_phy_get(to_of_node(dpmac_node), NULL);
> > +
> > +		if (IS_ERR(serdes_phy)) {
> > +			if (PTR_ERR(serdes_phy) == -ENODEV)
> > +				serdes_phy = NULL;
> > +			else
> > +				return PTR_ERR(serdes_phy);
> > +		} else {
> > +			phy_init(serdes_phy);
> > +		}
> 
> Would:
> 		if (PTR_ERR(serdes_phy) == -ENODEV)
> 			serdes_phy = NULL;
> 		else if (IS_ERR(serdes_phy))
> 			return PTR_ERR(serdes_phy);
> 		else
> 			phy_init(serdes_phy);
> 

Yes, it wouldn't be an if inside another if statement.

> be neater? There is no need to check IS_ERR() before testing PTR_ERR().
> One may also prefer the pointer-comparison approach:
> 
> 		if (serdes_phy == ERR_PTR(-ENODEV))
> 
> to remove any question about PTR_ERR(p) on a !IS_ERR(p) value too, but
> it really doesn't make any difference.
> 
> I suspect this is just a code formatting issue, I'd think the compiler
> would generate reasonable code either way, so as I said above, it's
> quite minor.
> 

As you said, since it's quite minor I am going to wait to see if more
comments will appear, if not I am going to fix this up in another patch.

Thanks!