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(p200300EA8BC4DC00E99B2537DCD3443F.dip0.t-ipconnect.de. [2003:ea:8bc4:dc00:e99b:2537:dcd3:443f]) by smtp.googlemail.com with ESMTPSA id 11sm3614341wmg.27.2019.03.15.16.14.10 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 Mar 2019 16:14:11 -0700 (PDT) Subject: Re: [PATCH net] net: phy: Don't assume loopback is supported To: Jose Abreu , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Andrew Lunn , Florian Fainelli , "David S. Miller" , Joao Pinto References: From: Heiner Kallweit Message-ID: <24bb3e68-402b-98c1-a9e5-ca72e8efe428@gmail.com> Date: Sat, 16 Mar 2019 00:14:06 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.3 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 14.03.2019 11:37, Jose Abreu wrote: > Some PHYs may not support loopback mode so we need to check if register > is read-only. > As I read Clause 22 this is a mandatory feature, the related bit is specified as R/W. Do you have an actual example of a PHY w/o loopback mode that doesn't allow to change this bit? > Fixes: f0f9b4ed2338 ("net: phy: Add phy loopback support in net phy framework") > Signed-off-by: Jose Abreu > Cc: Andrew Lunn > Cc: Florian Fainelli > Cc: "David S. Miller" > Cc: Joao Pinto > --- > drivers/net/phy/phy_device.c | 20 ++++++++++++++++++-- > 1 file changed, 18 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c > index 49fdd1ee798e..a749639d98c3 100644 > --- a/drivers/net/phy/phy_device.c > +++ b/drivers/net/phy/phy_device.c > @@ -1918,8 +1918,24 @@ EXPORT_SYMBOL(genphy_resume); > > int genphy_loopback(struct phy_device *phydev, bool enable) > { > - return phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK, > - enable ? BMCR_LOOPBACK : 0); > + int ret; > + > + ret = phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK, > + enable ? BMCR_LOOPBACK : 0); > + if (ret < 0) > + return ret; > + > + ret = phy_read(phydev, MII_BMCR); > + if (ret < 0) > + return ret; > + > + if (enable) { > + if (ret & BMCR_LOOPBACK) > + return 0; > + return -EOPNOTSUPP; > + } > + > + return 0; > } > EXPORT_SYMBOL(genphy_loopback); > >