9757f8af04
Driver fastpath employs doorbells to indicate to the device that work is available. Each doorbell translates to a message sent to the device over PCI. These messages are queued by the doorbell queue HW block, and handled by the HW. If a sufficient amount of CPU cores are sending messages at a sufficient rate, the queue can overflow, and messages can be dropped. There are many entities in the driver which can send doorbell messages. When overflow happens, a fatal HW attention is indicated, and the Doorbell HW block stops accepting new doorbell messages until recovery procedure is done. When overflow occurs, all doorbells are dropped. Since doorbells are aggregatives, if more doorbells are sent nothing has to be done. But if the "last" doorbell is dropped, the doorbelling entity doesn’t know this happened, and may wait forever for the device to perform the action. The doorbell recovery mechanism addresses just that - it sends the last doorbell of every entity. [mkp: fix missing brackets reported by Guenter Roeck] Link: https://lore.kernel.org/r/20210804221412.5048-1-smalin@marvell.com Co-developed-by: Manish Rangankar <mrangankar@marvell.com> Signed-off-by: Manish Rangankar <mrangankar@marvell.com> Signed-off-by: Shai Malin <smalin@marvell.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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.