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For hosts not supporting MMC_CAP2_SDIO_IRQ_NOTHREAD but MMC_CAP_SDIO_IRQ, the SDIO IRQs are processed from a dedicated kernel thread. For these cases, the host calls mmc_signal_sdio_irq() from its ISR to signal a new SDIO IRQ. Signaling an SDIO IRQ makes the host's ->enable_sdio_irq() callback to be invoked to temporary disable the IRQs, before the kernel thread is woken up to process it. When processing of the IRQs are completed, they are re-enabled by the kernel thread, again via invoking the host's ->enable_sdio_irq(). The observation from this, is that the execution path is being unnecessary complex, as the host driver already knows that it needs to temporary disable the IRQs before signaling a new one. Moreover, replacing the kernel thread with a work/workqueue would not only greatly simplify the code, but also make it more robust. To address the above problems, let's continue to build upon the support for MMC_CAP2_SDIO_IRQ_NOTHREAD, as it already implements SDIO IRQs to be processed without using the clumsy kernel thread and without the ping-pong calls of the host's ->enable_sdio_irq() callback for each processed IRQ. Therefore, let's add new API sdio_signal_irq(), which enables hosts to signal/process SDIO IRQs by using a work/workqueue, rather than using the kernel thread. Add also a new host callback ->ack_sdio_irq(), which the work invokes when the SDIO IRQs have been processed. This informs the host about when it shall re-enable the SDIO IRQs. Potentially, we could re-use the existing ->enable_sdio_irq() callback instead of adding a new one, however it has turned out that it's more convenient for hosts to get this information via a separate callback. Hosts that wants to use this new method to signal/process SDIO IRQs, must enable MMC_CAP2_SDIO_IRQ_NOTHREAD and implement the ->ack_sdio_irq() callback. Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> Tested-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Douglas Anderson <dianders@chromium.org>
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.