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81196e2e57
Some fault events like the over-current condition will get resolved by the hardware, by e.g. disabling the port. As the status in the interrupt status register is cleared on read when the fault is resolved, the sysfs health property will only contain the correct health status for the first time it is read after such an event, even if the actual fault condition (like a VBUS short) still persists. To reflect this properly in the property we cache the last health status and only update the cache when a actual change happens, i.e. the ERR bit in the status register flips, as this one properly reflects a continued fault condition. The ALERT pin however, is not driven by the ERR status, but by the actual fault status, so the pin will change back to it's default state when the hardware has automatically resolved the fault by cutting the power. Thus we never get an IRQ when the actual fault condition has been resolved and the ERR status bit has been cleared in auto-recovery mode. To get this information we need to poll the interrupt status register after some time to see if the fault is gone and update our cache in that case. To avoid any additional locking, we handle both paths (IRQ firing and delayed polling) through the same single-threaded delayed work. Signed-off-by: Lucas Stach <l.stach@pengutronix.de> Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com> |
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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 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.