Hello Dan, Am 08.03.19 um 18:25 schrieb Dan Murphy: > On 3/8/19 11:08 AM, Wolfgang Grandegger wrote: >> 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 <dmurphy@xxxxxx> >>>>>>>> --- >>>>>>>> >>>>>>>> >>>>>>>> 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? >> > > I am not seeing where we are not handling the message in the m_can_tx_handler() static void m_can_tx_handler(struct m_can_classdev *priv) { ... /* Check if FIFO full */ if (m_can_tx_fifo_full(priv)) { /* This shouldn't happen */ netif_stop_queue(dev); netdev_warn(dev, "TX queue active although FIFO is full."); return; } We simply return here. When is the message (tx_skb) processed (sent or freed)? What happens with tx_skb? For the hi3110, we have: static void hi3110_tx_work_handler(struct work_struct *ws) { struct hi3110_priv *priv = container_of(ws, struct hi3110_priv, tx_work); struct spi_device *spi = priv->spi; struct net_device *net = priv->net; struct can_frame *frame; mutex_lock(&priv->hi3110_lock); if (priv->tx_skb) { if (priv->can.state == CAN_STATE_BUS_OFF) { hi3110_clean(net); } else { frame = (struct can_frame *)priv->tx_skb->data; hi3110_hw_tx(spi, frame); priv->tx_len = 1 + frame->can_dlc; can_put_echo_skb(priv->tx_skb, net, 0); priv->tx_skb = NULL; } } mutex_unlock(&priv->hi3110_lock); } Either the tx_skb is sent or cleanup (dropped and freed) in case of bus-off. Also "hi3110_clean" sets "priv->tx_skb = NULL"! The "tx_len" handles a pending "echo_skb". > > In the peripheral code the work is queued up. And the work thread is m_can_tx_work_queue. > > This in turn calls the m_can_tx_handler and the worker is blocked until return which means the message > would have been processed. > > If there is no issue and the handler returns OK then the skb is set to null. > Otherwise the only other time that the skb will not be null is if the FIFO was full. > > Plus there can only be one work queue at a time so the processing is synchronous. > If the upper layer decides to send another packet before the prior one is complete then it will get > a TX busy return. > > IOmapped calls are blocked on return so this is not an issue. We cannot do it the same way with peripherals due to the > atomic context of the request. Wolfgang.
