[PATCH] soundwire: stream: Use polling for DP Prepare completion

[Richard Fitzgerald]

sdw_prep_deprep_slave_ports() cannot use the port interrupt to signal
CP_SM completion because it is called while holding the bus lock, which
blocks the alert handler from running.

Change to polling the PREPARESTATUS register and remove the
infrastructure that was implemented for the previous interrupt waiting.

A new configuration field 'ch_prep_poll_us' is added to struct
sdw_dpn_prop so that the peripheral driver may select a polling interval.
If this is left at zero a default interval of 500 usec is used.

Signed-off-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx>
---
 drivers/soundwire/bus.c       |  2 --
 drivers/soundwire/slave.c     |  4 ----
 drivers/soundwire/stream.c    | 24 ++++++++++++++----------
 include/linux/soundwire/sdw.h |  8 ++++++--
 4 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index adcbf3969110..606fc26d407f 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -1351,7 +1351,6 @@ static int sdw_handle_dp0_interrupt(struct sdw_slave *slave, u8 *slave_status)
 		 */
 
 		if (status & SDW_DP0_INT_PORT_READY) {
-			complete(&slave->port_ready[0]);
 			clear |= SDW_DP0_INT_PORT_READY;
 		}
 
@@ -1429,7 +1428,6 @@ static int sdw_handle_port_interrupt(struct sdw_slave *slave,
 		 * for ports implementing CP_SM.
 		 */
 		if (status & SDW_DPN_INT_PORT_READY) {
-			complete(&slave->port_ready[port]);
 			clear |= SDW_DPN_INT_PORT_READY;
 		}
 
diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/slave.c
index 669d7573320b..55ca884ea951 100644
--- a/drivers/soundwire/slave.c
+++ b/drivers/soundwire/slave.c
@@ -26,7 +26,6 @@ int sdw_slave_add(struct sdw_bus *bus,
 {
 	struct sdw_slave *slave;
 	int ret;
-	int i;
 
 	slave = kzalloc(sizeof(*slave), GFP_KERNEL);
 	if (!slave)
@@ -62,9 +61,6 @@ int sdw_slave_add(struct sdw_bus *bus,
 	slave->probed = false;
 	slave->first_interrupt_done = false;
 
-	for (i = 0; i < SDW_MAX_PORTS; i++)
-		init_completion(&slave->port_ready[i]);
-
 	mutex_lock(&bus->bus_lock);
 	list_add_tail(&slave->node, &bus->slaves);
 	mutex_unlock(&bus->bus_lock);
diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
index 1eaedaaba094..bd6b3b64de90 100644
--- a/drivers/soundwire/stream.c
+++ b/drivers/soundwire/stream.c
@@ -8,11 +8,13 @@
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/init.h>
+#include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 #include <linux/slab.h>
 #include <linux/soundwire/sdw_registers.h>
 #include <linux/soundwire/sdw.h>
+#include <linux/time.h>
 #include <sound/soc.h>
 #include "bus.h"
 
@@ -419,11 +421,10 @@ static int sdw_prep_deprep_slave_ports(struct sdw_bus *bus,
 				       struct sdw_port_runtime *p_rt,
 				       bool prep)
 {
-	struct completion *port_ready;
 	struct sdw_dpn_prop *dpn_prop;
 	struct sdw_prepare_ch prep_ch;
-	unsigned int time_left;
 	bool intr = false;
+	unsigned long prep_poll_us, prep_timeout_us;
 	int ret = 0, val;
 	u32 addr;
 
@@ -478,16 +479,19 @@ static int sdw_prep_deprep_slave_ports(struct sdw_bus *bus,
 		}
 
 		/* Wait for completion on port ready */
-		port_ready = &s_rt->slave->port_ready[prep_ch.num];
-		time_left = wait_for_completion_timeout(port_ready,
-				msecs_to_jiffies(dpn_prop->ch_prep_timeout));
+		prep_timeout_us = dpn_prop->ch_prep_timeout * USEC_PER_MSEC;
+		if (dpn_prop->ch_prep_poll_us)
+			prep_poll_us = dpn_prop->ch_prep_poll_us;
+		else
+			prep_poll_us = SDW_DEFAULT_DP_PREP_POLL_US;
 
-		val = sdw_read(s_rt->slave, SDW_DPN_PREPARESTATUS(p_rt->num));
-		val &= p_rt->ch_mask;
-		if (!time_left || val) {
+		ret = read_poll_timeout(sdw_read, val, ((val & p_rt->ch_mask) == 0),
+					prep_poll_us, prep_timeout_us, false,
+					s_rt->slave, SDW_DPN_PREPARESTATUS(p_rt->num));
+		if (ret < 0) {
 			dev_err(&s_rt->slave->dev,
-				"Chn prep failed for port:%d\n", prep_ch.num);
-			return -ETIMEDOUT;
+				"Chn prep failed for port %d: %d\n", prep_ch.num, ret);
+			return ret;
 		}
 	}
 
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
index ddbeb00799e4..4e5290b083bf 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -67,6 +67,9 @@ enum {
 #define SDW_BLOCK_PACKG_PER_PORT	BIT(0)
 #define SDW_BLOCK_PACKG_PER_CH		BIT(1)
 
+/* Default interval to poll for DP prepare completion */
+#define SDW_DEFAULT_DP_PREP_POLL_US	500
+
 /**
  * enum sdw_slave_status - Slave status
  * @SDW_SLAVE_UNATTACHED: Slave is not attached with the bus.
@@ -295,6 +298,8 @@ struct sdw_dpn_audio_mode {
  * @simple_ch_prep_sm: If the port supports simplified channel prepare state
  * machine
  * @ch_prep_timeout: Port-specific timeout value, in milliseconds
+ * @ch_prep_poll_us: Interval to poll for CP_SM prepare completion. Zero means
+ *                   poll at SDW_DEFAULT_DP_PREP_POLL_US intervals.
  * @imp_def_interrupts: If set, each bit corresponds to support for
  * implementation-defined interrupts
  * @max_ch: Maximum channels supported
@@ -321,6 +326,7 @@ struct sdw_dpn_prop {
 	u32 max_grouping;
 	bool simple_ch_prep_sm;
 	u32 ch_prep_timeout;
+	u32 ch_prep_poll_us;
 	u32 imp_def_interrupts;
 	u32 max_ch;
 	u32 min_ch;
@@ -641,7 +647,6 @@ struct sdw_slave_ops {
  * @prop: Slave properties
  * @debugfs: Slave debugfs
  * @node: node for bus list
- * @port_ready: Port ready completion flag for each Slave port
  * @m_port_map: static Master port map for each Slave port
  * @dev_num: Current Device Number, values can be 0 or dev_num_sticky
  * @dev_num_sticky: one-time static Device Number assigned by Bus
@@ -673,7 +678,6 @@ struct sdw_slave {
 	struct dentry *debugfs;
 #endif
 	struct list_head node;
-	struct completion port_ready[SDW_MAX_PORTS];
 	unsigned int m_port_map[SDW_MAX_PORTS];
 	u16 dev_num;
 	u16 dev_num_sticky;
-- 
2.20.1