• Ulf Hansson's avatar
    mmc: sdio: Add API to manage SDIO IRQs from a workqueue · 68269660
    Ulf Hansson authored
    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: default avatarUlf Hansson <ulf.hansson@linaro.org>
    Tested-by: default avatarDouglas Anderson <dianders@chromium.org>
    Reviewed-by: default avatarDouglas Anderson <dianders@chromium.org>
    68269660
host.c 11.9 KB