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 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. > > 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.
