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Fri, 8 Mar 2019 18:12:26 +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> <6016c8aa-01b6-38d5-0e1f-3a999aae6a13@ti.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: <1f6f77c6-dcf2-6212-5d4e-1eb699e603f1@grandegger.com> Date: Fri, 8 Mar 2019 18:08:36 +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: <6016c8aa-01b6-38d5-0e1f-3a999aae6a13@ti.com> 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, 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 >>>>>> --- >>>>>> >>>>>> >>>>>> 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.