From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfgang Grandegger Subject: Re: [PATCH v7 1/4] can: m_can: Create a m_can platform framework Date: Fri, 8 Mar 2019 15:41:39 +0100 Message-ID: References: <20190305155220.14037-1-dmurphy@ti.com> <5065d6ba-f195-a695-77b1-b837cac1a199@grandegger.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org To: Dan Murphy , mkl@pengutronix.de, davem@davemloft.net Cc: linux-can@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-can.vger.kernel.org Hello Dan, thinking more about it... Am 08.03.19 um 14:29 schrieb Wolfgang Grandegger: > Hello Dan, > > Am 08.03.19 um 13:44 schrieb Dan Murphy: >> Wolfgang >> >> On 3/8/19 4:10 AM, Wolfgang Grandegger wrote: >>> Hallo Dan, >>> >>> Am 05.03.19 um 16:52 schrieb Dan Murphy: >>>> Create a m_can platform framework that peripherial >>>> devices can register to and use common code and register sets. >>>> The peripherial devices may provide read/write and configuration >>>> support of the IP. >>>> >>>> Signed-off-by: Dan Murphy >>>> --- >>>> >>>> >>>> v7 - Fixed remaining new checkpatch issues, removed CSR setting, fixed tx hard >>>> start function to return tx_busy, and renamed device callbacks - https://lore.kernel.org/patchwork/patch/1047220/ >>>> >>>> v6 - Squashed platform patch to this patch for bissectablity, fixed coding style >>>> issues, updated Kconfig help, placed mcan reg offsets back into c file, renamed >>>> priv->skb to priv->tx_skb and cleared perp interrupts at ISR start - >>>> Patch 1 comments - https://lore.kernel.org/patchwork/patch/1042446/ >>>> Patch 2 comments - https://lore.kernel.org/patchwork/patch/1042442/ >>>> >>>> drivers/net/can/m_can/Kconfig | 13 +- >>>> drivers/net/can/m_can/Makefile | 1 + >>>> drivers/net/can/m_can/m_can.c | 700 +++++++++++++------------ >>>> drivers/net/can/m_can/m_can.h | 110 ++++ >>>> drivers/net/can/m_can/m_can_platform.c | 202 +++++++ >>>> 5 files changed, 682 insertions(+), 344 deletions(-) >>>> create mode 100644 drivers/net/can/m_can/m_can.h >>>> create mode 100644 drivers/net/can/m_can/m_can_platform.c >>>> >>>> diff --git a/drivers/net/can/m_can/Kconfig b/drivers/net/can/m_can/Kconfig >>>> index 04f20dd39007..f7119fd72df4 100644 >>>> --- a/drivers/net/can/m_can/Kconfig >>>> +++ b/drivers/net/can/m_can/Kconfig >>>> @@ -1,5 +1,14 @@ >>>> config CAN_M_CAN >>>> + tristate "Bosch M_CAN support" >>>> + ---help--- >>>> + Say Y here if you want support for Bosch M_CAN controller framework. >>>> + This is common support for devices that embed the Bosch M_CAN IP. >>>> + >>>> +config CAN_M_CAN_PLATFORM >>>> + tristate "Bosch M_CAN support for io-mapped devices" >>>> depends on HAS_IOMEM >>>> - tristate "Bosch M_CAN devices" >>>> + depends on CAN_M_CAN >>>> ---help--- >>>> - Say Y here if you want to support for Bosch M_CAN controller. >>>> + Say Y here if you want support for IO Mapped Bosch M_CAN controller. >>>> + This support is for devices that have the Bosch M_CAN controller >>>> + IP embedded into the device and the IP is IO Mapped to the processor. >>>> diff --git a/drivers/net/can/m_can/Makefile b/drivers/net/can/m_can/Makefile >>>> index 8bbd7f24f5be..057bbcdb3c74 100644 >>>> --- a/drivers/net/can/m_can/Makefile >>>> +++ b/drivers/net/can/m_can/Makefile >>>> @@ -3,3 +3,4 @@ >>>> # >>>> >>>> obj-$(CONFIG_CAN_M_CAN) += m_can.o >>>> +obj-$(CONFIG_CAN_M_CAN_PLATFORM) += m_can_platform.o >>>> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c >>>> index 9b449400376b..a60278d94126 100644 >>>> --- a/drivers/net/can/m_can/m_can.c >>>> +++ b/drivers/net/can/m_can/m_can.c >>> >>> ... snip... >>> >>>> +static netdev_tx_t m_can_start_xmit(struct sk_buff *skb, >>>> + struct net_device *dev) >>>> +{ >>>> + struct m_can_priv *priv = netdev_priv(dev); >>>> + >>>> + if (can_dropped_invalid_skb(dev, skb)) >>>> + return NETDEV_TX_OK; >>>> + >>>> + if (priv->is_peripherial) { >>>> + if (priv->tx_skb) { >>>> + netdev_err(dev, "hard_xmit called while tx busy\n"); >>>> + return NETDEV_TX_BUSY; >>>> + } >>> >>> The problem with that approach is, that the upper layer will try to >>> resubmit the current "skb" but not the previous "tx_skb". And the >>> previous "tx_skb" has not been freed yet. I would just drop and free the >>> skb and return NETDEV_TX_OK in m_can_tx_handler() for peripheral devices >>> (like can_dropped_invalid_skb() does). >>> >> >> OK. >> >> So would this also be a bug in the hi3110 and mcp251x drivers (line 521) as well because besides checking tx_length >> this is how these drivers are written. > > This is different. When entering the "start_xmit" routine, the previous > TX is still in progress. It will (hopefully) complete soon. Therefore > returning NETDEV_TX_BUSY is OK. The "start_xmit" routine will be > recalled soon with the same "skb". That scenario should/could also not > happen. In principle, this also applies to the m_can peripheral devices. If tx_skb is not NULL, the TX is still in progress and returning NETDEV_TX_BUSY is just fine. > > In contrast, in "m_can_tx_handler()", the skb could not be handled > because the FIFO is full. The "start_xmit" routine for peripheral > devices for that skb already returned NETDEV_TX_OK. Therefore the only > meaningful action is to drop the skb. Also this error should not happen > and if, something is going really wrong. Therefore I think, a > WARN_ONCE() would be even more appropriate. But that should be a > separate patch. But that's a different issue/error. The tx_skb cannot be processed in "m_can_tx_handler()". Either we drop it or we re-queue it (retry later). >> >> In addition in the peripheral context the work queue does not report up to the upper layer the status. >> Again the hi3110 and mcp251x drivers are written this way. >> >> The only issue I see here is that the dropped and invalid check needs to come after the tx_skb check. > > See above. Wolfgang.