[PATCH] soundwire: cadence: only prepare attached devices on clock stop

[Bard Liao]

From: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>

We sometimes see COMMAND_IGNORED responses during the clock stop
sequence. It turns out we already have information if devices are
present on a link, so we should only prepare those when they
are attached.

In addition, even when COMMAND_IGNORED are received, we should still
proceed with the clock stop. The device will not be prepared but
that's not a problem.

The only case where the clock stop will fail is if the Cadence IP
reports an error (including a timeout), or if the devices throw a
COMMAND_FAILED response.

BugLink: https://github.com/thesofproject/linux/issues/2621
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
Reviewed-by: Rander Wang <rander.wang at intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski at linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao at linux.intel.com>
---
 drivers/soundwire/cadence_master.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index d05442e646a3..57c59a33ce61 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -1450,10 +1450,12 @@ int sdw_cdns_clock_stop(struct sdw_cdns *cdns, bool block_wake)
 	}
 
 	/* Prepare slaves for clock stop */
-	ret = sdw_bus_prep_clk_stop(&cdns->bus);
-	if (ret < 0) {
-		dev_err(cdns->dev, "prepare clock stop failed %d", ret);
-		return ret;
+	if (slave_present) {
+		ret = sdw_bus_prep_clk_stop(&cdns->bus);
+		if (ret < 0 && ret != -ENODATA) {
+			dev_err(cdns->dev, "prepare clock stop failed %d\n", ret);
+			return ret;
+		}
 	}
 
 	/*
-- 
2.17.1