Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752840AbdHJP3d (ORCPT ); Thu, 10 Aug 2017 11:29:33 -0400 Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:58521 "EHLO metis.ext.4.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752297AbdHJP3b (ORCPT ); Thu, 10 Aug 2017 11:29:31 -0400 Subject: Re: [PATCH v4 1/4] can: dev: Add support for limiting configured bitrate To: Franklin S Cooper Jr , linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, netdev@vger.kernel.org, linux-can@vger.kernel.org, wg@grandegger.com, robh+dt@kernel.org, quentin.schulz@free-electrons.com, dev.kurt@vandijck-laurijssen.be, andrew@lunn.ch, sergei.shtylyov@cogentembedded.com, socketcan@hartkopp.net References: <20170810005916.27163-1-fcooper@ti.com> <20170810005916.27163-2-fcooper@ti.com> From: Marc Kleine-Budde Message-ID: <4a96c6a8-b8c5-24a1-5e99-44751a0ae987@pengutronix.de> Date: Thu, 10 Aug 2017 17:29:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170810005916.27163-2-fcooper@ti.com> Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="mMhkTxquGB5jERDiHjS8tXtRJOWrPlaQf" X-SA-Exim-Connect-IP: 2001:67c:670:201:5054:ff:fe8d:eefb X-SA-Exim-Mail-From: mkl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6718 Lines: 205 This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --mMhkTxquGB5jERDiHjS8tXtRJOWrPlaQf Content-Type: multipart/mixed; boundary="2H0fqbPv56hvmkDXmofDteMS09jVhdKAu"; protected-headers="v1" From: Marc Kleine-Budde To: Franklin S Cooper Jr , linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, netdev@vger.kernel.org, linux-can@vger.kernel.org, wg@grandegger.com, robh+dt@kernel.org, quentin.schulz@free-electrons.com, dev.kurt@vandijck-laurijssen.be, andrew@lunn.ch, sergei.shtylyov@cogentembedded.com, socketcan@hartkopp.net Message-ID: <4a96c6a8-b8c5-24a1-5e99-44751a0ae987@pengutronix.de> Subject: Re: [PATCH v4 1/4] can: dev: Add support for limiting configured bitrate References: <20170810005916.27163-1-fcooper@ti.com> <20170810005916.27163-2-fcooper@ti.com> In-Reply-To: <20170810005916.27163-2-fcooper@ti.com> --2H0fqbPv56hvmkDXmofDteMS09jVhdKAu Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: quoted-printable Hello, sorry for stepping in late.... On 08/10/2017 02:59 AM, Franklin S Cooper Jr wrote: > Various CAN or CAN-FD IP may be able to run at a faster rate than > what the transceiver the CAN node is connected to. This can lead to > unexpected errors. However, CAN transceivers typically have fixed > limitations and provide no means to discover these limitations at > runtime. Therefore, add support for a can-transceiver node that > can be reused by other CAN peripheral drivers to determine for both > CAN and CAN-FD what the max bitrate that can be used. If the user > tries to configure CAN to pass these maximum bitrates it will throw > an error. >=20 > Signed-off-by: Franklin S Cooper Jr > --- > Version 4 changes: > Used can-transceiver instead of fixed-transceiver. >=20 > drivers/net/can/dev.c | 50 +++++++++++++++++++++++++++++++++++++++++= ++++++++ > include/linux/can/dev.h | 5 +++++ > 2 files changed, 55 insertions(+) >=20 > diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c > index 365a8cc..372108f 100644 > --- a/drivers/net/can/dev.c > +++ b/drivers/net/can/dev.c > @@ -27,6 +27,7 @@ > #include > #include > #include > +#include > #include > =20 > #define MOD_DESC "CAN device driver interface" > @@ -814,6 +815,39 @@ int open_candev(struct net_device *dev) > } > EXPORT_SYMBOL_GPL(open_candev); > =20 > +#ifdef CONFIG_OF > +/* > + * Common function that can be used to understand the limitation of > + * a transceiver when it provides no means to determine these limitati= ons > + * at runtime. > + */ > +void of_can_transceiver(struct net_device *dev) > +{ > + struct device_node *dn; > + struct can_priv *priv =3D netdev_priv(dev); > + struct device_node *np; > + unsigned int max_bitrate; > + int ret; > + > + np =3D dev->dev.parent->of_node; > + > + dn =3D of_get_child_by_name(np, "can-transceiver"); > + if (!dn) > + return; > + > + max_bitrate =3D 0; > + ret =3D of_property_read_u32(dn, "max-bitrate", &max_bitrate); IIRC the last argument is only modified in case of no error, so what abou= t: ret =3D of_property_read_u32(dn, "max-bitrate", &priv->max_bitrate); > + > + if (max_bitrate > 0) { > + priv->max_bitrate =3D max_bitrate; > + priv->is_bitrate_limited =3D true; Do we need is_bitrate_limited... > + } else if (ret !=3D -EINVAL) { > + netdev_warn(dev, "Invalid value for transceiver max bitrate\n"); > + } > +} > +EXPORT_SYMBOL(of_can_transceiver); > +#endif > + > /* > * Common close function for cleanup before the device gets closed. > * > @@ -913,6 +947,14 @@ static int can_changelink(struct net_device *dev, = struct nlattr *tb[], > priv->bitrate_const_cnt); > if (err) > return err; > + > + if (priv->is_bitrate_limited && > + bt.bitrate > priv->max_bitrate) { =2E..can we just use priv->max_bitrate? if (priv->max_bitrate && bt.bitrate > priv->max_bitrate) > + netdev_err(dev, "arbitration bitrate surpasses transceiver capabili= ties of %d bps\n", > + priv->max_bitrate); > + return -EINVAL; > + } > + > memcpy(&priv->bittiming, &bt, sizeof(bt)); > =20 > if (priv->do_set_bittiming) { > @@ -997,6 +1039,14 @@ static int can_changelink(struct net_device *dev,= struct nlattr *tb[], > priv->data_bitrate_const_cnt); > if (err) > return err; > + > + if (priv->is_bitrate_limited && > + dbt.bitrate > priv->max_bitrate) { > + netdev_err(dev, "canfd data bitrate surpasses transceiver capabilit= ies of %d bps\n", > + priv->max_bitrate); > + return -EINVAL; > + } > + > memcpy(&priv->data_bittiming, &dbt, sizeof(dbt)); > =20 > if (priv->do_set_data_bittiming) { > diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h > index 141b05a..5519f59 100644 > --- a/include/linux/can/dev.h > +++ b/include/linux/can/dev.h > @@ -47,6 +47,9 @@ struct can_priv { > unsigned int data_bitrate_const_cnt; > struct can_clock clock; > =20 > + unsigned int max_bitrate; > + bool is_bitrate_limited; > + > enum can_state state; > =20 > /* CAN controller features - see include/uapi/linux/can/netlink.h */ > @@ -165,6 +168,8 @@ void can_put_echo_skb(struct sk_buff *skb, struct n= et_device *dev, > unsigned int can_get_echo_skb(struct net_device *dev, unsigned int idx= ); > void can_free_echo_skb(struct net_device *dev, unsigned int idx); > =20 > +void of_can_transceiver(struct net_device *dev); > + > struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame= **cf); > struct sk_buff *alloc_canfd_skb(struct net_device *dev, > struct canfd_frame **cfd); >=20 Marc --=20 Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de | --2H0fqbPv56hvmkDXmofDteMS09jVhdKAu-- --mMhkTxquGB5jERDiHjS8tXtRJOWrPlaQf Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEE4bay/IylYqM/npjQHv7KIOw4HPYFAlmMe8kACgkQHv7KIOw4 HPbtKggAltn42+XOFBPtjBR0Zdf948NmpxpxAKtGVvnHjVuOE10m5M2GVFftg2Dm 7ewHJj/G72bfN/V1VpBvljCuWnqzoFPWwZwPU4R7kPrZku2LEHfv7wq9M2f8nN8n JJB9oITPPFqaYhoAWQWodJWFtlFXellUxZc7fjmsY1DlzWQyCrxvkEpd8afSfD1U CZOfp7kkGYqloeVeCUcjSL4D+rr4ljMKxXYW/p1ftsoT2Zz0/ddfTrUY03DMTEBN N1RblAXo6lGbNXowNF2uLO7w+y9FXIYOhUeZCJYT5PeL01Ebz2RuYWWyYWQXA8v0 wJXZwsClX8KzdKnAngQ6oI9KkssoIQ== =sBn7 -----END PGP SIGNATURE----- --mMhkTxquGB5jERDiHjS8tXtRJOWrPlaQf--