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In preparation for adaptive IRQ coalescing, we first need to support adjusting the settings at runtime. The existing code doesn't require any locking because - dma_start is the only function that modifies rx/tx_dma_cr. It is always called with IRQs and NAPI disabled, so nothing else is touching the hardware. - The IRQs don't race with poll, since the latter is a softirq. - The IRQs don't race with dma_stop since they both just clear the control registers. - dma_stop doesn't race with poll since the former is called with NAPI disabled. However, once we introduce another function that modifies rx/tx_dma_cr, we need to have some locking to prevent races. Introduce two locks to protect these variables and their registers. The control register values are now generated where the coalescing settings are set. Converting coalescing settings to control register values may require sleeping because of clk_get_rate. However, the read/modify/write of the control registers themselves can't sleep because it needs to happen in IRQ context. By pre-calculating the control register values, we avoid introducing an additional mutex. Since axienet_dma_start writes the control settings when it runs, we don't bother updating the CR registers when rx/tx_dma_started is false. This prevents any issues from writing to the control registers in the middle of a reset sequence. Signed-off-by: Sean Anderson <sean.anderson@linux.dev> Reviewed-by: Shannon Nelson <shannon.nelson@amd.com> Link: https://patch.msgid.link/20250206201036.1516800-3-sean.anderson@linux.dev Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
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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.