Hello, Am 08.03.19 um 16:48 schrieb Dan Murphy: > Wolfgang > > On 3/8/19 8:41 AM, Wolfgang Grandegger wrote: >> 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 <dmur...@ti.com> >>>>>> --- >>>>>> >>>>>> >>>>>> 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). >> > > OK I am a bit confused on this. Are you saying this is not an issue? > Or are you saying I need to check for tx_len like the other code?
If you check for tx_skb in the "start_xmit" routine like the hi3110 and mcp251x, it will work the same way. But only, if the "tx_handler()" has fully processed the message. It simple means, the TX is still in progress and will complete soon. But in "m_can_tx_handler()" we return without handling the message! It will never be sent and freed. Or will the "m_can_tx_handler()" retry? > Again if this code is an issue here I believe this is an issue in the hi3110 > and mcp251x I don't think so. Sorry for confusion. Wolfgang.
