linux-kernel - [RFC PATCH 40/40] soundwire: intel: add delay on restart for enumeration

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Date:   Thu, 25 Jul 2019 18:40:32 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     alsa-devel@...a-project.org
Cc:     linux-kernel@...r.kernel.org, tiwai@...e.de, broonie@...nel.org,
        vkoul@...nel.org, gregkh@...uxfoundation.org, jank@...ence.com,
        srinivas.kandagatla@...aro.org, slawomir.blauciak@...el.com,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>
Subject: [RFC PATCH 40/40] soundwire: intel: add delay on restart for enumeration

We have a conceptual issue on restart: the interaction with the slaves
can start before (re) enumeration is complete. Add a delay for now but
we will need to have an async notification that all devices are back
on the bus.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
---
 drivers/soundwire/intel.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
index 1394a2322553..e4ea430b5a8e 100644
--- a/drivers/soundwire/intel.c
+++ b/drivers/soundwire/intel.c
@@ -1242,6 +1242,11 @@ static int intel_resume(struct device *dev)
 
 	ret = sdw_cdns_exit_reset(&sdw->cdns);
 
+	/* add delay to let Slaves re-enumerate */
+	usleep_range(20000, 30000);
+
+	dev_dbg(dev, "%s done\n", __func__);
+
 	return ret;
 }
 
-- 
2.20.1