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Spending time under spinlock increases IRQ latencies and also response times because preemption is disabled. sdhci_send_command() waits up to 10 ms under spinlock for inhibit bits to clear. In general inhibit bits will not be set, but there may be corner cases, especially in the face of errors, where waiting helps. There might also be dysfunctional hardware that needs the waiting. So retain the legacy behaviour but do not wait for inhibit bits while under spinlock. Instead adjust the logic to enable waiting while not under spinlock. That is mostly straight forward, but in the interrupt handler it requires deferring an "inhibited" command to the IRQ thread where sleeping is allowed. Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Tested-by: Baolin Wang <baolin.wang7@gmail.com> Link: https://lore.kernel.org/r/20200412090349.1607-6-adrian.hunter@intel.com Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
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.