[alsa-devel] [PATCH v3 22/22] soundwire: intel: pm_runtime idle scheduling

[Pierre-Louis Bossart]

Add quirk and pm_runtime idle scheduling to let the Master suspend if
no Slaves become attached. This can happen when a link is not marked
as disabled and has devices exposed in the DSDT, if the power is
controlled by sideband means or the link includes a pluggable
connector.

Signed-off-by: Rander Wang <rander.wang at linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
---
 drivers/soundwire/intel.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
index b114e9a72fdc..f0077f58c4bf 100644
--- a/drivers/soundwire/intel.c
+++ b/drivers/soundwire/intel.c
@@ -29,8 +29,9 @@
  * flags reused in each byte, with master0 using the ls-byte, etc.
  */
 
-#define SDW_INTEL_MASTER_DISABLE_PM_RUNTIME BIT(0)
-#define SDW_INTEL_MASTER_DISABLE_CLOCK_STOP BIT(1)
+#define SDW_INTEL_MASTER_DISABLE_PM_RUNTIME		BIT(0)
+#define SDW_INTEL_MASTER_DISABLE_CLOCK_STOP		BIT(1)
+#define SDW_INTEL_MASTER_DISABLE_PM_RUNTIME_IDLE	BIT(2)
 
 static int md_flags;
 module_param_named(sdw_md_flags, md_flags, int, 0444);
@@ -1329,6 +1330,22 @@ static int intel_master_startup(struct sdw_master_device *md)
 		pm_runtime_enable(&md->dev);
 	}
 
+	/*
+	 * Slave devices have an pm_runtime of 'Unsupported' until
+	 * they report as ATTACHED. If they don't, e.g. because there
+	 * are no Slave devices populated or if the power-on is
+	 * delayed or dependent on a power switch, the Master will
+	 * remain active and prevent its parent from suspending.
+	 *
+	 * Conditionally force the pm_runtime core to re-evaluate the
+	 * Master status in the absence of any Slave activity. A quirk
+	 * is provided to e.g. deal with Slaves that may be powered on
+	 * with a delay. A more complete solution would require the
+	 * definition of Master properties.
+	 */
+	if (!(link_flags & SDW_INTEL_MASTER_DISABLE_PM_RUNTIME_IDLE))
+		pm_runtime_idle(&md->dev);
+
 	return 0;
 
 err_interrupt:
@@ -1443,6 +1460,7 @@ static int intel_resume(struct device *dev)
 	struct sdw_master_device *md = to_sdw_master_device(dev);
 	struct sdw_cdns *cdns = dev_get_drvdata(dev);
 	struct sdw_intel *sdw = cdns_to_intel(cdns);
+	int link_flags;
 	int ret;
 
 	if (cdns->bus.prop.hw_disabled) {
@@ -1463,6 +1481,10 @@ static int intel_resume(struct device *dev)
 		pm_runtime_enable(dev);
 
 		md->pm_runtime_suspended = false;
+
+		link_flags = md_flags >> (sdw->cdns.bus.link_id * 8);
+		if (!(link_flags & SDW_INTEL_MASTER_DISABLE_PM_RUNTIME_IDLE))
+			pm_runtime_idle(&md->dev);
 	}
 
 	ret = intel_init(sdw);
-- 
2.20.1