Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752616AbeACMTW (ORCPT + 1 other); Wed, 3 Jan 2018 07:19:22 -0500 Received: from fllnx210.ext.ti.com ([198.47.19.17]:59795 "EHLO fllnx210.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751733AbeACMTT (ORCPT ); Wed, 3 Jan 2018 07:19:19 -0500 Subject: Re: [PATCH v6 1/6] can: dev: Add support for limiting configured bitrate To: Marc Kleine-Budde , , , CC: , , , , , , , , References: <1513949488-13026-1-git-send-email-faiz_abbas@ti.com> <1513949488-13026-2-git-send-email-faiz_abbas@ti.com> From: Faiz Abbas Message-ID: Date: Wed, 3 Jan 2018 17:49:33 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: Hi Marc, On Tuesday 02 January 2018 06:30 PM, Marc Kleine-Budde wrote: > On 12/22/2017 02:31 PM, Faiz Abbas wrote: >> From: Franklin S Cooper Jr >> >> 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 >> [nsekhar@ti.com: fix build error with !CONFIG_OF] >> Signed-off-by: Sekhar Nori >> Signed-off-by: Faiz Abbas >> --- >> v6 changes: >> fix build error with !CONFIG_OF >> >> drivers/net/can/dev.c | 39 +++++++++++++++++++++++++++++++++++++++ >> include/linux/can/dev.h | 8 ++++++++ >> 2 files changed, 47 insertions(+) >> >> diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c >> index 365a8cc..007cfc0 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 +815,30 @@ 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 = dev->dev.parent->of_node; >> + int ret; >> + >> + dn = of_get_child_by_name(np, "can-transceiver"); >> + if (!dn) >> + return; >> + >> + ret = of_property_read_u32(dn, "max-bitrate", &priv->max_bitrate); >> + if ((ret && ret != -EINVAL) || (!ret && !priv->max_bitrate)) >> + netdev_warn(dev, "Invalid value for transceiver max bitrate. Ignoring bitrate limit.\n"); >> +} >> +EXPORT_SYMBOL_GPL(of_can_transceiver); >> +#endif >> + >> /* >> * Common close function for cleanup before the device gets closed. >> * >> @@ -913,6 +938,13 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[], >> priv->bitrate_const_cnt); >> if (err) >> return err; >> + >> + 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; >> + } > > What about movong this check into can_get_bittiming()? Although we loose > the "arbitration" vs "canfd data". I would prefer to keep the distinction. > >> + >> memcpy(&priv->bittiming, &bt, sizeof(bt)); >> >> if (priv->do_set_bittiming) { >> @@ -997,6 +1029,13 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[], >> priv->data_bitrate_const_cnt); >> if (err) >> return err; >> + >> + if (priv->max_bitrate && 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 61f1cf2..fbb7810 100644 >> --- a/include/linux/can/dev.h >> +++ b/include/linux/can/dev.h >> @@ -48,6 +48,8 @@ struct can_priv { >> unsigned int data_bitrate_const_cnt; >> struct can_clock clock; >> >> + unsigned int max_bitrate; > > Please make it an u32, name it "bitrate_max" and ... Sure. > >>> struct can_priv { >>> struct net_device *dev; >>> struct can_device_stats can_stats; >>> >>> struct can_bittiming bittiming, data_bittiming; >>> const struct can_bittiming_const *bittiming_const, >>> *data_bittiming_const; >>> const u16 *termination_const; >>> unsigned int termination_const_cnt; >>> u16 termination; >>> const u32 *bitrate_const; >>> unsigned int bitrate_const_cnt; >>> const u32 *data_bitrate_const; >>> unsigned int data_bitrate_const_cnt; > > ...move it here. Ok. Thanks, Faiz