soundwire: intel/cadence: fix startup sequence

Multiple changes squashed in single patch to avoid tick-tock effect
and avoid breaking compilation/bisect

1. Per the hardware documentation, all changes to MCP_CONFIG,
MCP_CONTROL, MCP_CMDCTRL and MCP_PHYCTRL need to be validated with a
self-clearing write to MCP_CONFIG_UPDATE. Add a helper and do the
update when the CONFIG is changed.

2. Move interrupt enable after interrupt handler registration

3. Add a new helper to start the hardware bus reset with maximum duration
to make sure the Slave(s) correctly detect the reset pattern and to
ensure electrical conflicts can be resolved.

4. flush command FIFOs

Better error handling will be provided after interrupt disable is
provided in follow-up patches.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20191022235448.17586-2-pierre-louis.bossart@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

1 files changed, 56 insertions, 24 deletions

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index dbe386e179b4..5337ccacccd1 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -229,6 +229,22 @@ static int cdns_clear_bit(struct sdw_cdns *cdns, int offset, u32 value)
 }
 
 /*
+ * all changes to the MCP_CONFIG, MCP_CONTROL, MCP_CMDCTRL and MCP_PHYCTRL
+ * need to be confirmed with a write to MCP_CONFIG_UPDATE
+ */
+static int cdns_update_config(struct sdw_cdns *cdns)
+{
+	int ret;
+
+	ret = cdns_clear_bit(cdns, CDNS_MCP_CONFIG_UPDATE,
+			     CDNS_MCP_CONFIG_UPDATE_BIT);
+	if (ret < 0)
+		dev_err(cdns->dev, "Config update timedout\n");
+
+	return ret;
+}
+
+/*
  * debugfs
  */
 #ifdef CONFIG_DEBUG_FS
@@ -745,7 +761,38 @@ EXPORT_SYMBOL(sdw_cdns_thread);
 /*
  * init routines
  */
-static int _cdns_enable_interrupt(struct sdw_cdns *cdns)
+
+/**
+ * sdw_cdns_exit_reset() - Program reset parameters and start bus operations
+ * @cdns: Cadence instance
+ */
+int sdw_cdns_exit_reset(struct sdw_cdns *cdns)
+{
+	/* program maximum length reset to be safe */
+	cdns_updatel(cdns, CDNS_MCP_CONTROL,
+		     CDNS_MCP_CONTROL_RST_DELAY,
+		     CDNS_MCP_CONTROL_RST_DELAY);
+
+	/* use hardware generated reset */
+	cdns_updatel(cdns, CDNS_MCP_CONTROL,
+		     CDNS_MCP_CONTROL_HW_RST,
+		     CDNS_MCP_CONTROL_HW_RST);
+
+	/* enable bus operations with clock and data */
+	cdns_updatel(cdns, CDNS_MCP_CONFIG,
+		     CDNS_MCP_CONFIG_OP,
+		     CDNS_MCP_CONFIG_OP_NORMAL);
+
+	/* commit changes */
+	return cdns_update_config(cdns);
+}
+EXPORT_SYMBOL(sdw_cdns_exit_reset);
+
+/**
+ * sdw_cdns_enable_interrupt() - Enable SDW interrupts and update config
+ * @cdns: Cadence instance
+ */
+int sdw_cdns_enable_interrupt(struct sdw_cdns *cdns)
 {
 	u32 mask;
 
@@ -777,24 +824,8 @@ static int _cdns_enable_interrupt(struct sdw_cdns *cdns)
 
 	cdns_writel(cdns, CDNS_MCP_INTMASK, mask);
 
-	return 0;
-}
-
-/**
- * sdw_cdns_enable_interrupt() - Enable SDW interrupts and update config
- * @cdns: Cadence instance
- */
-int sdw_cdns_enable_interrupt(struct sdw_cdns *cdns)
-{
-	int ret;
-
-	_cdns_enable_interrupt(cdns);
-	ret = cdns_clear_bit(cdns, CDNS_MCP_CONFIG_UPDATE,
-			     CDNS_MCP_CONFIG_UPDATE_BIT);
-	if (ret < 0)
-		dev_err(cdns->dev, "Config update timedout\n");
-
-	return ret;
+	/* commit changes */
+	return cdns_update_config(cdns);
 }
 EXPORT_SYMBOL(sdw_cdns_enable_interrupt);
 
@@ -955,6 +986,10 @@ int sdw_cdns_init(struct sdw_cdns *cdns)
 	cdns_writel(cdns, CDNS_MCP_SSP_CTRL0, CDNS_DEFAULT_SSP_INTERVAL);
 	cdns_writel(cdns, CDNS_MCP_SSP_CTRL1, CDNS_DEFAULT_SSP_INTERVAL);
 
+	/* flush command FIFOs */
+	cdns_updatel(cdns, CDNS_MCP_CONTROL, CDNS_MCP_CONTROL_CMD_RST,
+		     CDNS_MCP_CONTROL_CMD_RST);
+
 	/* Set cmd accept mode */
 	cdns_updatel(cdns, CDNS_MCP_CONTROL, CDNS_MCP_CONTROL_CMD_ACCEPT,
 		     CDNS_MCP_CONTROL_CMD_ACCEPT);
@@ -977,13 +1012,10 @@ int sdw_cdns_init(struct sdw_cdns *cdns)
 	/* Set cmd mode for Tx and Rx cmds */
 	val &= ~CDNS_MCP_CONFIG_CMD;
 
-	/* Set operation to normal */
-	val &= ~CDNS_MCP_CONFIG_OP;
-	val |= CDNS_MCP_CONFIG_OP_NORMAL;
-
 	cdns_writel(cdns, CDNS_MCP_CONFIG, val);
 
-	return 0;
+	/* commit changes */
+	return cdns_update_config(cdns);
 }
 EXPORT_SYMBOL(sdw_cdns_init);