Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753832AbdHQSGd (ORCPT ); Thu, 17 Aug 2017 14:06:33 -0400 Received: from lelnx193.ext.ti.com ([198.47.27.77]:38836 "EHLO lelnx193.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753788AbdHQSGa (ORCPT ); Thu, 17 Aug 2017 14:06:30 -0400 Subject: Re: [PATCH v4 1/4] can: dev: Add support for limiting configured bitrate To: Marc Kleine-Budde , , , , , , , , , , , References: <20170810005916.27163-1-fcooper@ti.com> <20170810005916.27163-2-fcooper@ti.com> <4a96c6a8-b8c5-24a1-5e99-44751a0ae987@pengutronix.de> From: Franklin S Cooper Jr Message-ID: <193455e6-524a-4897-cba0-5c37a943827f@ti.com> Date: Thu, 17 Aug 2017 13:05:52 -0500 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: <4a96c6a8-b8c5-24a1-5e99-44751a0ae987@pengutronix.de> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [128.247.59.135] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4878 Lines: 157 Hi, On 08/10/2017 10:29 AM, Marc Kleine-Budde wrote: > 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. >> >> Signed-off-by: Franklin S Cooper Jr >> --- >> Version 4 changes: >> Used can-transceiver instead of fixed-transceiver. >> >> drivers/net/can/dev.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++ >> include/linux/can/dev.h | 5 +++++ >> 2 files changed, 55 insertions(+) >> >> 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 >> >> #define MOD_DESC "CAN device driver interface" >> @@ -814,6 +815,39 @@ int open_candev(struct net_device *dev) >> } >> EXPORT_SYMBOL_GPL(open_candev); >> >> +#ifdef CONFIG_OF >> +/* >> + * Common function that can be used to understand the limitation of >> + * a transceiver when it provides no means to determine these limitations >> + * at runtime. >> + */ >> +void of_can_transceiver(struct net_device *dev) >> +{ >> + struct device_node *dn; >> + struct can_priv *priv = netdev_priv(dev); >> + struct device_node *np; >> + unsigned int max_bitrate; >> + int ret; >> + >> + np = dev->dev.parent->of_node; >> + >> + dn = of_get_child_by_name(np, "can-transceiver"); >> + if (!dn) >> + return; >> + >> + max_bitrate = 0; >> + ret = of_property_read_u32(dn, "max-bitrate", &max_bitrate); > > IIRC the last argument is only modified in case of no error, so what about: > ret = of_property_read_u32(dn, "max-bitrate", > &priv->max_bitrate); That works > >> + >> + if (max_bitrate > 0) { >> + priv->max_bitrate = max_bitrate; >> + priv->is_bitrate_limited = true; > > Do we need is_bitrate_limited... No. > >> + } else if (ret != -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) { > > ...can we just use priv->max_bitrate? Yes Thanks for reviewing and for your feedback. > > if (priv->max_bitrate && bt.bitrate > priv->max_bitrate) > >> + netdev_err(dev, "arbitration bitrate surpasses transceiver capabilities of %d bps\n", >> + priv->max_bitrate); >> + return -EINVAL; >> + } >> + >> memcpy(&priv->bittiming, &bt, sizeof(bt)); >> >> 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 capabilities of %d bps\n", >> + priv->max_bitrate); >> + return -EINVAL; >> + } >> + >> memcpy(&priv->data_bittiming, &dbt, sizeof(dbt)); >> >> 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; >> >> + unsigned int max_bitrate; >> + bool is_bitrate_limited; >> + >> enum can_state state; >> >> /* CAN controller features - see include/uapi/linux/can/netlink.h */ >> @@ -165,6 +168,8 @@ void can_put_echo_skb(struct sk_buff *skb, struct net_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); >> >> +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); >> > > Marc >