[PATCH v7 4/4] CMDQ: suspend/resume protection

[HS Liao]

Add suspend/resume protection mechanism to prevent active task(s) in
suspend.

Signed-off-by: HS Liao <hs.liao@xxxxxxxxxxxx>
---
 drivers/soc/mediatek/mtk-cmdq.c | 174 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 166 insertions(+), 8 deletions(-)

diff --git a/drivers/soc/mediatek/mtk-cmdq.c b/drivers/soc/mediatek/mtk-cmdq.c
index f8c5d02..1a51cfb 100644
--- a/drivers/soc/mediatek/mtk-cmdq.c
+++ b/drivers/soc/mediatek/mtk-cmdq.c
@@ -39,6 +39,7 @@
 #define CMDQ_CLK_NAME			"gce"
 
 #define CMDQ_CURR_IRQ_STATUS		0x010
+#define CMDQ_CURR_LOADED_THR		0x018
 #define CMDQ_THR_SLOT_CYCLES		0x030
 
 #define CMDQ_THR_BASE			0x100
@@ -125,6 +126,7 @@ enum cmdq_code {
 
 enum cmdq_task_state {
 	TASK_STATE_BUSY,	/* task running on a thread */
+	TASK_STATE_KILLED,	/* task process being killed */
 	TASK_STATE_ERROR,	/* task execution error */
 	TASK_STATE_DONE,	/* task finished */
 };
@@ -161,8 +163,12 @@ struct cmdq {
 	u32			irq;
 	struct workqueue_struct	*task_release_wq;
 	struct cmdq_thread	thread[CMDQ_THR_MAX_COUNT];
-	spinlock_t		exec_lock;	/* for exec task */
+	atomic_t		thread_usage;
+	struct mutex		task_mutex;	/* for task */
+	spinlock_t		exec_lock;	/* for exec */
 	struct clk		*clock;
+	bool			suspending;
+	bool			suspended;
 };
 
 struct cmdq_subsys {
@@ -196,15 +202,27 @@ static int cmdq_eng_get_thread(u64 flag)
 		return CMDQ_THR_DISP_MISC_IDX;
 }
 
-static void cmdq_task_release(struct cmdq_task *task)
+static void cmdq_task_release_unlocked(struct cmdq_task *task)
 {
 	struct cmdq *cmdq = task->cmdq;
 
+	/* This func should be inside cmdq->task_mutex mutex */
+	lockdep_assert_held(&cmdq->task_mutex);
+
 	dma_free_coherent(cmdq->dev, task->command_size, task->va_base,
 			  task->mva_base);
 	kfree(task);
 }
 
+static void cmdq_task_release(struct cmdq_task *task)
+{
+	struct cmdq *cmdq = task->cmdq;
+
+	mutex_lock(&cmdq->task_mutex);
+	cmdq_task_release_unlocked(task);
+	mutex_unlock(&cmdq->task_mutex);
+}
+
 static struct cmdq_task *cmdq_task_acquire(struct cmdq_rec *rec,
 					   struct cmdq_task_cb cb)
 {
@@ -576,6 +594,12 @@ static int cmdq_task_wait_and_release(struct cmdq_task *task)
 		dev_dbg(dev, "timeout!\n");
 
 	spin_lock_irqsave(&cmdq->exec_lock, flags);
+
+	if (cmdq->suspending && task->task_state == TASK_STATE_KILLED) {
+		spin_unlock_irqrestore(&cmdq->exec_lock, flags);
+		return 0;
+	}
+
 	if (task->task_state != TASK_STATE_DONE)
 		err = cmdq_task_handle_error_result(task);
 	if (list_empty(&thread->task_busy_list))
@@ -584,7 +608,9 @@ static int cmdq_task_wait_and_release(struct cmdq_task *task)
 
 	/* release regardless of success or not */
 	clk_disable_unprepare(cmdq->clock);
-	cmdq_task_release(task);
+	atomic_dec(&cmdq->thread_usage);
+	if (!(task->cmdq->suspending && task->task_state == TASK_STATE_KILLED))
+		cmdq_task_release(task);
 
 	return err;
 }
@@ -597,12 +623,28 @@ static void cmdq_task_wait_release_work(struct work_struct *work_item)
 	cmdq_task_wait_and_release(task);
 }
 
-static void cmdq_task_wait_release_schedule(struct cmdq_task *task)
+static void cmdq_task_wait_release_schedule(struct cmdq *cmdq,
+					    struct cmdq_task *task)
 {
-	struct cmdq *cmdq = task->cmdq;
+	unsigned long flags;
+
+	spin_lock_irqsave(&cmdq->exec_lock, flags);
+
+	if (cmdq->suspending || cmdq->suspended) {
+		/*
+		 * This means system is suspened between
+		 * cmdq_task_submit_async() and
+		 * cmdq_task_wait_release_schedule(), so return immediately.
+		 * This task should be forced to remove by suspend flow.
+		 */
+		spin_unlock_irqrestore(&cmdq->exec_lock, flags);
+		return;
+	}
 
 	INIT_WORK(&task->release_work, cmdq_task_wait_release_work);
 	queue_work(cmdq->task_release_wq, &task->release_work);
+
+	spin_unlock_irqrestore(&cmdq->exec_lock, flags);
 }
 
 static int cmdq_rec_realloc_cmd_buffer(struct cmdq_rec *rec, size_t size)
@@ -766,18 +808,31 @@ static int _cmdq_rec_flush(struct cmdq_rec *rec, struct cmdq_task **task_out,
 	struct cmdq_thread *thread;
 	int err;
 
+	mutex_lock(&cmdq->task_mutex);
+	if (rec->cmdq->suspending || rec->cmdq->suspended) {
+		dev_err(rec->cmdq->dev,
+			"%s is called after suspending\n", __func__);
+		mutex_unlock(&cmdq->task_mutex);
+		return -EPERM;
+	}
+
 	err = cmdq_rec_finalize(rec);
-	if (err < 0)
+	if (err < 0) {
+		mutex_unlock(&cmdq->task_mutex);
 		return err;
+	}
 
 	task_cb.cb = cb;
 	task_cb.data = data;
 	*task_out = cmdq_task_acquire(rec, task_cb);
-	if (!(*task_out))
+	if (!(*task_out)) {
+		mutex_unlock(&cmdq->task_mutex);
 		return -EFAULT;
+	}
 
 	thread = &cmdq->thread[cmdq_eng_get_thread((*task_out)->engine_flag)];
 	cmdq_task_exec(*task_out, thread);
+	mutex_unlock(&cmdq->task_mutex);
 	return 0;
 }
 
@@ -802,7 +857,13 @@ int cmdq_rec_flush_async(struct cmdq_rec *rec, cmdq_async_flush_cb cb,
 	err = _cmdq_rec_flush(rec, &task, cb, data);
 	if (err < 0)
 		return err;
-	cmdq_task_wait_release_schedule(task);
+
+	/*
+	 * Task could be released in suspend flow,
+	 * so we have to pass cmdq as parameter.
+	 */
+	cmdq_task_wait_release_schedule(rec->cmdq, task);
+
 	return 0;
 }
 EXPORT_SYMBOL(cmdq_rec_flush_async);
@@ -814,6 +875,95 @@ void cmdq_rec_destroy(struct cmdq_rec *rec)
 }
 EXPORT_SYMBOL(cmdq_rec_destroy);
 
+static int cmdq_suspend(struct device *dev)
+{
+	struct cmdq *cmdq = dev_get_drvdata(dev);
+	u32 exec_threads;
+	int ref_count;
+	unsigned long flags;
+	struct cmdq_thread *thread;
+	struct cmdq_task *task, *tmp;
+	int i;
+
+	/* lock to prevent new tasks */
+	mutex_lock(&cmdq->task_mutex);
+	cmdq->suspending = true;
+
+	exec_threads = readl(cmdq->base + CMDQ_CURR_LOADED_THR);
+	ref_count = atomic_read(&cmdq->thread_usage);
+	if (ref_count <= 0 && !(exec_threads & CMDQ_THR_EXECUTING))
+		goto exit;
+
+	dev_err(dev, "suspend: kill running, tasks.\n");
+	dev_err(dev, "threads: 0x%08x, ref:%d\n", exec_threads, ref_count);
+
+	/*
+	 * We need to ensure the system is ready to suspend,
+	 * so kill all running CMDQ tasks and release HW engines.
+	 */
+
+	/* remove all active tasks from thread and disable thread */
+	for (i = 0; i < ARRAY_SIZE(cmdq->thread); i++) {
+		thread = &cmdq->thread[i];
+
+		if (list_empty(&thread->task_busy_list))
+			continue;
+
+		/* prevent clk disable in release flow */
+		clk_prepare_enable(cmdq->clock);
+		cmdq_thread_suspend(cmdq, thread);
+
+		list_for_each_entry_safe(task, tmp, &thread->task_busy_list,
+					 list_entry) {
+			bool already_done = false;
+
+			spin_lock_irqsave(&cmdq->exec_lock, flags);
+			if (task->task_state == TASK_STATE_BUSY) {
+				/* still wait_event */
+				list_del(&task->list_entry);
+				task->task_state = TASK_STATE_KILLED;
+			} else {
+				/* almost finish its work */
+				already_done = true;
+			}
+			spin_unlock_irqrestore(&cmdq->exec_lock, flags);
+
+			/*
+			 * TASK_STATE_KILLED will unlock
+			 * wait_event_timeout in cmdq_task_wait_and_release(),
+			 * so flush_work to wait auto release flow.
+			 *
+			 * We don't know processes running order,
+			 * so call cmdq_task_release_unlocked() here to
+			 * prevent releasing task before flush_work, and
+			 * also to prevent deadlock of task_mutex.
+			 */
+			if (!already_done) {
+				flush_work(&task->release_work);
+				cmdq_task_release_unlocked(task);
+			}
+		}
+
+		cmdq_thread_resume(thread);
+		cmdq_thread_disable(cmdq, &cmdq->thread[i]);
+		clk_disable_unprepare(cmdq->clock);
+	}
+
+exit:
+	cmdq->suspended = true;
+	cmdq->suspending = false;
+	mutex_unlock(&cmdq->task_mutex);
+	return 0; /* ALWAYS allow suspend */
+}
+
+static int cmdq_resume(struct device *dev)
+{
+	struct cmdq *cmdq = dev_get_drvdata(dev);
+
+	cmdq->suspended = false;
+	return 0;
+}
+
 static int cmdq_remove(struct platform_device *pdev)
 {
 	struct cmdq *cmdq = platform_get_drvdata(pdev);
@@ -852,6 +1002,7 @@ static int cmdq_probe(struct platform_device *pdev)
 	dev_dbg(dev, "cmdq device: addr:0x%p, va:0x%p, irq:%d\n",
 		dev, cmdq->base, cmdq->irq);
 
+	mutex_init(&cmdq->task_mutex);
 	spin_lock_init(&cmdq->exec_lock);
 	cmdq->task_release_wq = alloc_ordered_workqueue(
 			"%s", WQ_MEM_RECLAIM | WQ_HIGHPRI,
@@ -879,6 +1030,7 @@ static int cmdq_probe(struct platform_device *pdev)
 		err = PTR_ERR(cmdq->clock);
 		goto fail;
 	}
+
 	return 0;
 
 fail:
@@ -886,6 +1038,11 @@ fail:
 	return err;
 }
 
+static const struct dev_pm_ops cmdq_pm_ops = {
+	.suspend = cmdq_suspend,
+	.resume = cmdq_resume,
+};
+
 static const struct of_device_id cmdq_of_ids[] = {
 	{.compatible = "mediatek,mt8173-gce",},
 	{}
@@ -897,6 +1054,7 @@ static struct platform_driver cmdq_drv = {
 	.driver = {
 		.name = CMDQ_DRIVER_DEVICE_NAME,
 		.owner = THIS_MODULE,
+		.pm = &cmdq_pm_ops,
 		.of_match_table = cmdq_of_ids,
 	}
 };
-- 
1.9.1