mainlining shenanigans
4c7f715485
As already mentioned in [1] and included in [2], there is an off by one issue since the high bank is already enabled when the _next_ mailbox to be read has index 12, so the mailbox being read was 13. The message can therefore go into mailbox 31 and the driver will be repolled until the mailbox 12 eventually receives a msg. Or the message might end up in the 12th mailbox, but then it would become disabled after reading it and only be enabled again in the next "round" after mailbox 13 was read, which can cause out of order messages, since the lower priority mailboxes can accept messages in the meantime. As mentioned in [3] there is a hardware race condition when changing the CANME register while messages are being received. Even when including a busy poll on reception, like in [2] there are still overflows and out of order messages at times, but less then without the busy loop polling. Unlike what the patch suggests, the polling time is not in the microsecond range, but takes as long as a current CAN bus reception needs to finish, so typically more in the fraction of millisecond range. Since the timeout is in jiffies it won't timeout. Even with these additional fixes the driver is still not able to provide a proper FIFO which doesn't drop packages. So change the driver to use rx-offload and base order on timestamp instead of message box numbers. As a side affect, this also fixes [4] and [5]. Before this change messages with a single byte counter were dropped / received out of order at a bitrate of 250kbit/s on an am3517. With this patch that no longer occurs up to and including 1Mbit/s. [1] https://linux-can.vger.kernel.narkive.com/zgO9inVi/patch-can-ti-hecc-fix-rx-wrong-sequence-issue#post6 [2] http://arago-project.org/git/projects/?p=linux-omap3.git;a=commit;h=02346892777f07245de4d5af692513ebd852dcb2 [3] https://linux-can.vger.kernel.narkive.com/zgO9inVi/patch-can-ti-hecc-fix-rx-wrong-sequence-issue#post5 [4] https://patchwork.ozlabs.org/patch/895956/ [5] https://www.spinics.net/lists/netdev/msg494971.html Cc: Anant Gole <anantgole@ti.com> Cc: AnilKumar Ch <anilkumar@ti.com> Signed-off-by: Jeroen Hofstee <jhofstee@victronenergy.com> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.