mmc: sdio: Add API to manage SDIO IRQs from a workqueue

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>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/mmc/core/sdio_irq.c b/drivers/mmc/core/sdio_irq.c
index 44d9c86bd2d4..c771843e4c15 100644
--- a/drivers/mmc/core/sdio_irq.c
+++ b/drivers/mmc/core/sdio_irq.c
@@ -98,11 +98,27 @@ void sdio_run_irqs(struct mmc_host *host)
 	if (host->sdio_irqs) {
 		host->sdio_irq_pending = true;
 		process_sdio_pending_irqs(host);
+		if (host->ops->ack_sdio_irq)
+			host->ops->ack_sdio_irq(host);
 	}
 	mmc_release_host(host);
 }
 EXPORT_SYMBOL_GPL(sdio_run_irqs);
 
+void sdio_irq_work(struct work_struct *work)
+{
+	struct mmc_host *host =
+		container_of(work, struct mmc_host, sdio_irq_work.work);
+
+	sdio_run_irqs(host);
+}
+
+void sdio_signal_irq(struct mmc_host *host)
+{
+	queue_delayed_work(system_wq, &host->sdio_irq_work, 0);
+}
+EXPORT_SYMBOL_GPL(sdio_signal_irq);
+
 static int sdio_irq_thread(void *_host)
 {
 	struct mmc_host *host = _host;