ASoC: intel: Replace kthread with work

The usage pattern of kthread worker in Intel SST drivers can be
replaced gracefully with the normal workqueue, which is more light-
weight and easier to manage in general.  Let's do it.

While in the replacement, move the schedule_work() call inside the
spinlock for excluding the race, too.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Tested-by: Subhransu S. Prusty <subhransu.s.prusty@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/baytrail/sst-baytrail-ipc.c

@@ -23,7 +23,6 @@
 #include <linux/slab.h>
 #include <linux/delay.h>
 #include <linux/platform_device.h>
-#include <linux/kthread.h>
 #include <linux/firmware.h>
 #include <linux/io.h>
 #include <asm/div64.h>
@@ -338,7 +337,7 @@ static irqreturn_t sst_byt_irq_thread(int irq, void *context)
 	spin_unlock_irqrestore(&sst->spinlock, flags);
 
 	/* continue to send any remaining messages... */
-	kthread_queue_work(&ipc->kworker, &ipc->kwork);
+	schedule_work(&ipc->kwork);
 
 	return IRQ_HANDLED;
 }

sound/soc/intel/common/sst-ipc.c

@@ -26,7 +26,6 @@
 #include <linux/sched.h>
 #include <linux/delay.h>
 #include <linux/platform_device.h>
-#include <linux/kthread.h>
 #include <sound/asound.h>
 
 #include "sst-dsp.h"
@@ -109,10 +108,9 @@ static int ipc_tx_message(struct sst_generic_ipc *ipc, u64 header,
 		ipc->ops.tx_data_copy(msg, tx_data, tx_bytes);
 
 	list_add_tail(&msg->list, &ipc->tx_list);
+	schedule_work(&ipc->kwork);
 	spin_unlock_irqrestore(&ipc->dsp->spinlock, flags);
 
-	kthread_queue_work(&ipc->kworker, &ipc->kwork);
-
 	if (wait)
 		return tx_wait_done(ipc, msg, rx_data);
 	else
@@ -156,35 +154,32 @@ static int msg_empty_list_init(struct sst_generic_ipc *ipc)
 	return -ENOMEM;
 }
 
-static void ipc_tx_msgs(struct kthread_work *work)
+static void ipc_tx_msgs(struct work_struct *work)
 {
 	struct sst_generic_ipc *ipc =
 		container_of(work, struct sst_generic_ipc, kwork);
 	struct ipc_message *msg;
-	unsigned long flags;
 
-	spin_lock_irqsave(&ipc->dsp->spinlock, flags);
+	spin_lock_irq(&ipc->dsp->spinlock);
 
-	if (list_empty(&ipc->tx_list) || ipc->pending) {
-		spin_unlock_irqrestore(&ipc->dsp->spinlock, flags);
-		return;
-	}
-
-	/* if the DSP is busy, we will TX messages after IRQ.
-	 * also postpone if we are in the middle of procesing completion irq*/
-	if (ipc->ops.is_dsp_busy && ipc->ops.is_dsp_busy(ipc->dsp)) {
-		dev_dbg(ipc->dev, "ipc_tx_msgs dsp busy\n");
-		spin_unlock_irqrestore(&ipc->dsp->spinlock, flags);
-		return;
-	}
+	while (!list_empty(&ipc->tx_list) && !ipc->pending) {
+		/* if the DSP is busy, we will TX messages after IRQ.
+		 * also postpone if we are in the middle of processing
+		 * completion irq
+		 */
+		if (ipc->ops.is_dsp_busy && ipc->ops.is_dsp_busy(ipc->dsp)) {
+			dev_dbg(ipc->dev, "ipc_tx_msgs dsp busy\n");
+			break;
+		}
 
-	msg = list_first_entry(&ipc->tx_list, struct ipc_message, list);
-	list_move(&msg->list, &ipc->rx_list);
+		msg = list_first_entry(&ipc->tx_list, struct ipc_message, list);
+		list_move(&msg->list, &ipc->rx_list);
 
-	if (ipc->ops.tx_msg != NULL)
-		ipc->ops.tx_msg(ipc, msg);
+		if (ipc->ops.tx_msg != NULL)
+			ipc->ops.tx_msg(ipc, msg);
+	}
 
-	spin_unlock_irqrestore(&ipc->dsp->spinlock, flags);
+	spin_unlock_irq(&ipc->dsp->spinlock);
 }
 
 int sst_ipc_tx_message_wait(struct sst_generic_ipc *ipc, u64 header,
@@ -305,19 +300,7 @@ int sst_ipc_init(struct sst_generic_ipc *ipc)
 	if (ret < 0)
 		return -ENOMEM;
 
-	/* start the IPC message thread */
-	kthread_init_worker(&ipc->kworker);
-	ipc->tx_thread = kthread_run(kthread_worker_fn,
-					&ipc->kworker, "%s",
-					dev_name(ipc->dev));
-	if (IS_ERR(ipc->tx_thread)) {
-		dev_err(ipc->dev, "error: failed to create message TX task\n");
-		ret = PTR_ERR(ipc->tx_thread);
-		kfree(ipc->msg);
-		return ret;
-	}
-
-	kthread_init_work(&ipc->kwork, ipc_tx_msgs);
+	INIT_WORK(&ipc->kwork, ipc_tx_msgs);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(sst_ipc_init);
@@ -326,8 +309,7 @@ void sst_ipc_fini(struct sst_generic_ipc *ipc)
 {
 	int i;
 
-	if (ipc->tx_thread)
-		kthread_stop(ipc->tx_thread);
+	cancel_work_sync(&ipc->kwork);
 
 	if (ipc->msg) {
 		for (i = 0; i < IPC_EMPTY_LIST_SIZE; i++) {

sound/soc/intel/common/sst-ipc.h

@@ -23,7 +23,6 @@
 #include <linux/list.h>
 #include <linux/workqueue.h>
 #include <linux/sched.h>
-#include <linux/kthread.h>
 
 #define IPC_MAX_MAILBOX_BYTES	256
 
@@ -66,8 +65,7 @@ struct sst_generic_ipc {
 	struct list_head empty_list;
 	wait_queue_head_t wait_txq;
 	struct task_struct *tx_thread;
-	struct kthread_worker kworker;
-	struct kthread_work kwork;
+	struct work_struct kwork;
 	bool pending;
 	struct ipc_message *msg;
 	int tx_data_max_size;

sound/soc/intel/haswell/sst-haswell-ipc.c

@@ -26,7 +26,6 @@
 #include <linux/delay.h>
 #include <linux/sched.h>
 #include <linux/platform_device.h>
-#include <linux/kthread.h>
 #include <linux/firmware.h>
 #include <linux/dma-mapping.h>
 #include <linux/debugfs.h>
@@ -818,7 +817,7 @@ static irqreturn_t hsw_irq_thread(int irq, void *context)
 	spin_unlock_irqrestore(&sst->spinlock, flags);
 
 	/* continue to send any remaining messages... */
-	kthread_queue_work(&ipc->kworker, &ipc->kwork);
+	schedule_work(&ipc->kwork);
 
 	return IRQ_HANDLED;
 }

sound/soc/intel/skylake/skl-sst-cldma.c

@@ -17,7 +17,6 @@
 
 #include <linux/device.h>
 #include <linux/mm.h>
-#include <linux/kthread.h>
 #include <linux/delay.h>
 #include "../common/sst-dsp.h"
 #include "../common/sst-dsp-priv.h"

sound/soc/intel/skylake/skl-sst-ipc.c

@@ -498,7 +498,7 @@ irqreturn_t skl_dsp_irq_thread_handler(int irq, void *context)
 	skl_ipc_int_enable(dsp);
 
 	/* continue to send any remaining messages... */
-	kthread_queue_work(&ipc->kworker, &ipc->kwork);
+	schedule_work(&ipc->kwork);
 
 	return IRQ_HANDLED;
 }

sound/soc/intel/skylake/skl-sst-ipc.h

@@ -16,7 +16,6 @@
 #ifndef __SKL_IPC_H
 #define __SKL_IPC_H
 
-#include <linux/kthread.h>
 #include <linux/irqreturn.h>
 #include "../common/sst-ipc.h"