Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.
Laurent Pinchart
authored
There's no reason to delay initialization of most of the driver (such as mapping memory I/O, getting clocks or enabling runtime PM) to the component master bind handler. This additionally fixes a real PM issue caused enabling runtime PM in the bind handler. The bind handler performs the following sequence of PM operations: pm_runtime_enable(dev); pm_runtime_get_sync(dev); ... (access the hardware to read the device revision) ... pm_runtime_put_sync(dev); If a failure occurs at this point, the error path calls pm_runtime_disable() to balance the pm_runtime_enable() call. To understand the problem, it should be noted that the bind handler is called when one of the component registers itself, which happens in the component's probe handler. Furthermore, as the components are children of the DSS, the device core calls pm_runtime_get_sync() on the DSS platform device before calling the component's probe handler. This increases the DSS power usage count but doesn't runtime resume the device, as runtime PM is disabled at that point. The bind handler is thus called with runtime PM disabled, with the device runtime suspended, but with the power usage count larger than 0. The pm_runtime_get_sync() call will thus further increase the power usage count and runtime resume the device. The pm_runtime_put_sync() handler will decrease the power usage count to a non-zero value and will thus not suspend the device. Finally, the pm_runtime_disable() call will disable runtime PM, preventing the pm_runtime_put() call in the device core from runtime suspending the device. The DSS device is thus left powered on. To fix this, move the initialization code from the bind handler to the probe handler. Signed-off-by:Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by:
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