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In the coresight CPU debug document it suggests to use 'echo' command to set latency request to /dev/cpu_dma_latency so can disable all CPU idle states, but in fact this doesn't work. This is because when the command 'echo' exits, it releases the device node's file descriptor and the kernel release function removes the QoS constraint; finally when the command 'echo' finished there have no constraint imposed on cpu_dma_latency. This patch changes to use 'exec' to access '/dev/cpu_dma_latency', the command 'exec' can avoid the file descriptor to be closed so we can keep the constraint on cpu_dma_latency. This patch also adds the info for reference docs for PM QoS and cpuidle sysfs. Cc: Jonathan Corbet <corbet@lwn.net> Cc: Sudeep Holla <sudeep.holla@arm.com> Reported-by: Kim Phillips <kim.phillips@arm.com> Suggested-by: Mathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by: Leo Yan <leo.yan@linaro.org> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
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| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
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| Makefile | ||
| README | ||
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.