soundwire: intel/cadence: merge Soundwire interrupt handlers/threads

The existing code uses one pair of interrupt handler/thread per link
but at the hardware level the interrupt is shared. This works fine for
legacy PCI interrupts, but leads to timeouts in MSI (Message-Signaled
Interrupt) mode, likely due to edges being lost.

This patch unifies interrupt handling for all links. The dedicated
handler is removed since we use a common one for all shared interrupt
sources, and the thread function takes care of dealing with interrupt
sources. This partition follows the model used for the SOF IPC on
HDaudio platforms, where similar timeout issues were noticed and doing
all the interrupt handling/clearing in the thread improved
reliability/stability.

Validation results with 4 links active in parallel show a night-and-day
improvement with no timeouts noticed even during stress tests. Latency
and quality of service are not affected by the change - mostly because
events on a SoundWire link are throttled by the bus frame rate
(typically 8..48kHz).

Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200716150947.22119-8-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/soundwire/intel_init.c b/drivers/soundwire/intel_init.c
index ad3175272e88..a97d3577eb57 100644
--- a/drivers/soundwire/intel_init.c
+++ b/drivers/soundwire/intel_init.c
@@ -9,6 +9,7 @@
 
 #include <linux/acpi.h>
 #include <linux/export.h>
+#include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
@@ -166,6 +167,19 @@ void sdw_intel_enable_irq(void __iomem *mmio_base, bool enable)
 }
 EXPORT_SYMBOL_NS(sdw_intel_enable_irq, SOUNDWIRE_INTEL_INIT);
 
+irqreturn_t sdw_intel_thread(int irq, void *dev_id)
+{
+	struct sdw_intel_ctx *ctx = dev_id;
+	struct sdw_intel_link_res *link;
+
+	list_for_each_entry(link, &ctx->link_list, list)
+		sdw_cdns_irq(irq, link->cdns);
+
+	sdw_intel_enable_irq(ctx->mmio_base, true);
+	return IRQ_HANDLED;
+}
+EXPORT_SYMBOL_NS(sdw_intel_thread, SOUNDWIRE_INTEL_INIT);
+
 static struct sdw_intel_ctx
 *sdw_intel_probe_controller(struct sdw_intel_res *res)
 {
@@ -209,6 +223,8 @@ static struct sdw_intel_ctx
 	link = ctx->links;
 	link_mask = ctx->link_mask;
 
+	INIT_LIST_HEAD(&ctx->link_list);
+
 	/* Create SDW Master devices */
 	for (i = 0; i < count; i++, link++) {
 		if (!(link_mask & BIT(i))) {
@@ -246,6 +262,9 @@ static struct sdw_intel_ctx
 			goto err;
 		}
 		link->pdev = pdev;
+		link->cdns = platform_get_drvdata(pdev);
+
+		list_add_tail(&link->list, &ctx->link_list);
 	}
 
 	return ctx;