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Fri, 8 Mar 2019 14:33:52 +0100 (CET) Subject: Re: [PATCH v7 1/4] can: m_can: Create a m_can platform framework To: Dan Murphy , mkl@pengutronix.de, davem@davemloft.net Cc: linux-can@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20190305155220.14037-1-dmurphy@ti.com> <5065d6ba-f195-a695-77b1-b837cac1a199@grandegger.com> From: Wolfgang Grandegger Openpgp: preference=signencrypt Autocrypt: addr=wg@grandegger.com; prefer-encrypt=mutual; keydata= mQINBFtEb5MBEAC5aRjs5jLwjbOaEE6rczZSqck7B3iGK8ldrV8HGSjxb1MAf4VbvDWrzXfA phEgX3e54AnYhnKcf6BA3J9TlSDdUAW7r/ijOFl+TehMz7holgjhlDK41acJ/klwXJotIqby bWqFgFw6o7b8hfbVzPi8Pz/+WOIKaDOb1Keb989mn253RF1yFakgvoQfCyAeVcnO5kcByW17 zbTEHsSduYi0Zir26Oedb2Vtas4SovrEXVh4e2dRdbEbHlI8po3Ih117CuGIPAe2RSfZKY88 8c9m+WsJKtrIDIMY+f5kcHG5mib++u1oTg7wjfFgTr925g2WjzT63YRibW8Vazot9yXquMo2 HYQStmnN9MuAkL/jslnxhGKNwTzpXv6FD2g/9hcLfSjaaCwGzj2j2ucJglJnO1n+ibVB14l2 JLVe+IKJaE1gvm2v9HPsE+o1P4O8I9iCiAbQ6BGUszHADOg7r8CeTQ+AOCypfEZ5l1Hwa3gw V+TtqyCU70U9LA0AKaDZ02vf0hFRWeXV/ErFq878GOXbbVMZu8G5aO0EcCBC75/KQnyi0WEl KVIcyTyxKel/Ext7vUFIkiA16JNWRpS85YDfe9CoEZcZK+nUU268j6Bp5a7MYaF/dZaLT+Du hLA82ry8IkPQvyV5yV+B0PwDM/w7de8zIzMy9YBXU8KGGDmgYQARAQABtCdXb2xmZ2FuZyBH cmFuZGVnZ2VyIDx3Z0BncmFuZGVnZ2VyLmNvbT6JAj8EEwECACkFAltEb5MCGyMFCQlmAYAH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRDwuz7LbZzIUhvED/4vTUqS0c/V5a4hc5Md u/8qkF7qg011tM0lXrZZxMQ8NrjdFuDhUefZ1q59QbLFU9da9D/CRVJUSx6BnY9jkR6lIm9l OGqS9ZlzubGXJCZhv1ONWPwY/i1RXTtauhRy+nkcyJk2Bzs5PWq1i4hWXpX//GfGUbCt+2bX 2+9bmHSPFtZ/MpIigS1E8RehIzlzqC/NCJspY8H0HKtLR6kpanRBYCuYSlBom/1LEP2MmXhh 9LgjQINp+jZJwnBj5L5JaUn/sg2WO+IiN6IphzyS2TvrlRhkhPJv5EOf0QmYzDgz5eU/h35x aCclLSJ0Go83GO0bXFGCzN86VreRgLRGTa7/x9VW05LiBdlsuLpG23IHM5f6p0WpYgE+jdri TrMued/DquQEcw/xNXpa3n9zTghLcWgcqGIdK3AE3yPjQBR3N6WoT4VOXnZjg6pyNHQ3W4qj LQgzJ3Tq2gPMhRLFcLXyk6V3rQ0ffn4LCXkFYVIBGAN8hHMOFeV6NESkUcEil6V4oOsLLGuJ XreFjAl1Cz3vIaVgzZEfub1z60DDM71lIr+UvWXLeMyKiSMWiJBPL3LUoUWmzpafaTJakDWm CEXa871Jlw7sy99MGVhiVG74JHjtPE6ontM1dKCP1+yT53TeGp1o/3Hj3sUielfDr5nV/kT6 p5zmgQN/1bJgV/3sKrkCDQRbRG+TARAA37mw9iosCWO5OtCrbvgJJwzOR3XrijVKi9KTNzDO NT2iy7teKP4+C+9why6iZhoJbBrTo56mbmI2nvfyOthxCa8nT14js8q0EgSMiyxXVeRvzEIQ sYcG4zgbGjwJ94Vrr5tMCFn5B6cYKJffTGmfY0D3b2V4GqaCGxVs3lWcQJeKl/raL8lp4YWz AI0jVx104W7rUbCTDvcSVfPqwM+9A6xaP4b1jwyYwGHgOTq6SeimRrGgM+UNtWqMU3+vUelG 8gKDyfIIo4IrceeHss5OuRREQZq5vNuzkeIY6faYWv65KT+IQ6EyC9UEGkMdcStfEsZO53Qq buA7Kha6lVViDM3vjGS+fnNq/od53dosWeWQ4O8M7Z6nxgp+EOPuJf041eKmIrcaRiXb+027 x4D0Kwv/xVsFa6cC2lkITWahENFIXwKOZ3imr2ZCtVF61qnm/GQ5P27JQKXMbPOM6wm0EjJ1 9t2EkSpgVHI0Cd0ldxD4eaGNwpeHJ5WGGzZrOE7PCcRziJX0qO/FpLjTQ6scf+bPACgduY71 AwXyA24mg7F2vK+Vth+Yp7MlgwYBMUy6D140jrkWrcRxKYfW1BgcKpbG/dh5DhUAvoOzFD7i zHrGK5FhzqJDBwKk7n9jGohf/MJWs2UKai/u4ogZBhhD5JPR8GG6VzO4snWisFLFuAEAEQEA AYkCJQQYAQIADwUCW0RvkwIbDAUJCWYBgAAKCRDwuz7LbZzIUkA3D/wJOvcQ7rTeoRiamOIB kD4n2Jsv8Vti/XfM0DTmhfnWL4y96VzSzNfl+EHAwXE4161qnXxTHnFK1hq7QklNdDiGW3iH nKZUyHUTnlUlCocv8jWtlqrpH0XVtF12JET65mE14Hga6BQ4ECXwU2GcP3202A55EzMj31b/ 59GD3CDIJy7bjQi+pIRuA9ZQRsFas7Od7AWO/nFns2wJ6AJkjXdCUCZ4iOuf82gLK9olDSmd H73Epc6l3jca62L2Lzei405LQSsfOZ06uH2aGPUJX4odUlEF6arm2j+9Q8Vyi4CJ316f2kAa sl7LhAwZtaj8hjl/PUWfd5w47dUBDUZjIRYcdM2TTU3Spgvg3zqXUzur5+r0jkUl2naeiSB1 vwjfIwnPqZOVr9FAXuLbAdUyCCC0ohGLrq5Nsc1A02rxpQHRxTSm2FOdn2jYvuD7JUgkhmUh /TXb8aL6A4hfX7oV4tGq7nSmDOCmgWRmAHAGp85fVq2iylCxZ1kKi8EYCSa28eQzetukFbAx JwmcrUSaCOK+jpHlNY0PkghSIzAE/7Se+c37unJ39xJLkrgehLYmUF7cBeNWhfchu4fAJosM 5mXohGkBKcd5YYmF13imYtAG5/VSmBm/0CFNGFO49MVTNGXGBznrPrWwtPZNwjJdi7JrvEbm 8QEfHnPzgykCs2DOOQ== Message-ID: Date: Fri, 8 Mar 2019 14:29:49 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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.