soundwire: intel: refine runtime pm for SDW_INTEL_CLK_STOP_BUS_RESET

When all the links are suspended, the HDaudio controller may suspend
and the power rails to the SoundWire IP may be disabled, requiring a
complete re-initialization/enumeration on resume. However, if one or
more Masters remained active, the HDaudio controller will remain active
and the power rails will remain enabled. As a result, during the link
resume step we can check if the context was preserved by verifying if
the clock was stopped, and avoid doing a complete bus reset and
re-enumeration.

Signed-off-by: Rander Wang <rander.wang@intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20200817152923.3259-13-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
index 2899445e2649eafeda5910ac0e0c543ff104f4ce..dbcbe2708563842daa9c85ae3b08e5f03bfa0aa0 100644 (file)
--- a/drivers/soundwire/intel.c
+++ b/drivers/soundwire/intel.c
@@ -1698,6 +1698,8 @@ static int intel_resume_runtime(struct device *dev)
        struct sdw_intel *sdw = cdns_to_intel(cdns);
        struct sdw_bus *bus = &cdns->bus;
        u32 clock_stop_quirks;
+       bool clock_stop0;
+       int status;
        int ret;
 
        if (bus->prop.hw_disabled) {
@@ -1739,11 +1741,24 @@ static int intel_resume_runtime(struct device *dev)
                        return ret;
                }
 
+               /*
+                * An exception condition occurs for the CLK_STOP_BUS_RESET
+                * case if one or more masters remain active. In this condition,
+                * all the masters are powered on for they are in the same power
+                * domain. Master can preserve its context for clock stop0, so
+                * there is no need to clear slave status and reset bus.
+                */
+               clock_stop0 = sdw_cdns_is_clock_stop(&sdw->cdns);
+
                /*
                 * make sure all Slaves are tagged as UNATTACHED and
                 * provide reason for reinitialization
                 */
-               sdw_clear_slave_status(bus, SDW_UNATTACH_REQUEST_MASTER_RESET);
+               if (!clock_stop0) {
+                       status = SDW_UNATTACH_REQUEST_MASTER_RESET;
+                       sdw_clear_slave_status(bus, status);
+               }
+
 
                ret = sdw_cdns_enable_interrupt(cdns, true);
                if (ret < 0) {
@@ -1751,7 +1766,7 @@ static int intel_resume_runtime(struct device *dev)
                        return ret;
                }
 
-               ret = sdw_cdns_clock_restart(cdns, true);
+               ret = sdw_cdns_clock_restart(cdns, !clock_stop0);
                if (ret < 0) {
                        dev_err(dev, "unable to restart clock during resume\n");
                        return ret;