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9065197e0d
Change the allocation strategy of the 8 SETUP registers from a least- recently-used (LRU) to a first-come-first-served basis. The AD7124 chips can have up to 16 channels enabled at a time in the sequencer for buffered reads, but only have 8 SETUP configurations (namely the OFFSET, GAIN, CONFIG and FILTER registers) that must be shared among the 16 channels. This means some of the channels must use the exact same configuration parameters so that they can share a single SETUP group of registers. The previous LRU strategy did not keep track of how many different configurations were requested at the same time, so if there were more than 8 different configurations requested, some channels would end up using the incorrect configuration because the slot assigned to them would also be assigned to a different configuration that wrote over it later. Adding such tracking to solve this would make an already complex algorithm even more complex. Instead we can replace it with a simpler first-come-first-serve strategy. This makes it easy to track how many different configurations are being requested at the same time. This comes at the expense of slightly longer setup times for buffered reads since all setup registers must be written each time when a buffered read is enabled. But this is generally not considered a hot path where performance is critical, so should be acceptable. This new strategy also makes hardware debugging easier since SETUPs are now assigned in a deterministic manner and in a logical order. Signed-off-by: David Lechner <dlechner@baylibre.com> Reviewed-by: Nuno Sá <nuno.sa@analog.com> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.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 reStructuredText 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.