[PATCH v2] mailbox: mtk-cmdq: Fix sleeping function called from invalid context

[Jason-JH.Lin]

When we run kernel with lockdebug option, we will get the BUG below:
[  106.692124] BUG: sleeping function called from invalid context at drivers/base/power/runtime.c:1164
[  106.692190] in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 3616, name: kworker/u17:3
[  106.692226] preempt_count: 1, expected: 0
[  106.692254] RCU nest depth: 0, expected: 0
[  106.692282] INFO: lockdep is turned off.
[  106.692306] irq event stamp: 0
[  106.692331] hardirqs last  enabled at (0): [<0000000000000000>] 0x0
[  106.692376] hardirqs last disabled at (0): [<ffffffee15d37fa0>] copy_process+0xc90/0x2ac0
[  106.692429] softirqs last  enabled at (0): [<ffffffee15d37fc4>] copy_process+0xcb4/0x2ac0
[  106.692473] softirqs last disabled at (0): [<0000000000000000>] 0x0
[  106.692513] CPU: 1 PID: 3616 Comm: kworker/u17:3 Not tainted 6.1.87-lockdep-14133-g26e933aca785 #1 6839942e1cf34914b0a366137843dd2366f52aa9
[  106.692556] Hardware name: Google Ciri sku0/unprovisioned board (DT)
[  106.692586] Workqueue: imgsys_runner imgsys_runner_func
[  106.692638] Call trace:
[  106.692662]  dump_backtrace+0x100/0x120
[  106.692702]  show_stack+0x20/0x2c
[  106.692737]  dump_stack_lvl+0x84/0xb4
[  106.692775]  dump_stack+0x18/0x48
[  106.692809]  __might_resched+0x354/0x4c0
[  106.692847]  __might_sleep+0x98/0xe4
[  106.692883]  __pm_runtime_resume+0x70/0x124
[  106.692921]  cmdq_mbox_send_data+0xe4/0xb1c
[  106.692964]  msg_submit+0x194/0x2dc
[  106.693003]  mbox_send_message+0x190/0x330
[  106.693043]  imgsys_cmdq_sendtask+0x1618/0x2224
[  106.693082]  imgsys_runner_func+0xac/0x11c
[  106.693118]  process_one_work+0x638/0xf84
[  106.693158]  worker_thread+0x808/0xcd0
[  106.693196]  kthread+0x24c/0x324
[  106.693231]  ret_from_fork+0x10/0x20

We found that there is a spin_lock_irqsave protection in msg_submit()
of mailbox.c and it is in the atomic context.
So when cmdq driver calls pm_runtime_get_sync() in cmdq_mbox_send_data(),
it will get this BUG report.

1. Change pm_runtime_get_sync() to pm_runtime_get() to avoid using sleep
   in atomic context.
2. Move clk_bulk_enable() outside cmdq_runtime_resume() to ensure GCE
   clocks are enabled before configuring GCE register.
3. Add used_count to avoid cmdq_runtime_suspend() being called before
   calling cmdq_runtime_resume().

Fixes: 8afe816b0c99 ("mailbox: mtk-cmdq-mailbox: Implement Runtime PM with autosuspend")
Signed-off-by: Jason-JH.Lin <jason-jh.lin at mediatek.com>
---
 drivers/mailbox/mtk-cmdq-mailbox.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/mailbox/mtk-cmdq-mailbox.c b/drivers/mailbox/mtk-cmdq-mailbox.c
index 033aff11f87c..b50f42e69aab 100644
--- a/drivers/mailbox/mtk-cmdq-mailbox.c
+++ b/drivers/mailbox/mtk-cmdq-mailbox.c
@@ -82,6 +82,7 @@ struct cmdq {
 	const struct gce_plat	*pdata;
 	struct cmdq_thread	*thread;
 	struct clk_bulk_data	clocks[CMDQ_GCE_NUM_MAX];
+	atomic_t		used_count;
 	bool			suspended;
 };
 
@@ -317,14 +318,21 @@ static int cmdq_runtime_resume(struct device *dev)
 {
 	struct cmdq *cmdq = dev_get_drvdata(dev);
 
-	return clk_bulk_enable(cmdq->pdata->gce_num, cmdq->clocks);
+	atomic_inc(&cmdq->used_count);
+	return 0;
 }
 
 static int cmdq_runtime_suspend(struct device *dev)
 {
 	struct cmdq *cmdq = dev_get_drvdata(dev);
 
+	if (atomic_read(&cmdq->used_count) == 0) {
+		dev_warn(dev, "%s when used_count is 0!", __func__);
+		return -EINVAL;
+	}
+
 	clk_bulk_disable(cmdq->pdata->gce_num, cmdq->clocks);
+	atomic_dec(&cmdq->used_count);
 	return 0;
 }
 
@@ -392,9 +400,8 @@ static int cmdq_mbox_send_data(struct mbox_chan *chan, void *data)
 	/* Client should not flush new tasks if suspended. */
 	WARN_ON(cmdq->suspended);
 
-	ret = pm_runtime_get_sync(cmdq->mbox.dev);
-	if (ret < 0)
-		return ret;
+	WARN_ON(pm_runtime_get(cmdq->mbox.dev) < 0);
+	WARN_ON(clk_bulk_enable(cmdq->pdata->gce_num, cmdq->clocks));
 
 	task = kzalloc(sizeof(*task), GFP_ATOMIC);
 	if (!task) {
@@ -465,7 +472,8 @@ static void cmdq_mbox_shutdown(struct mbox_chan *chan)
 	struct cmdq_task *task, *tmp;
 	unsigned long flags;
 
-	WARN_ON(pm_runtime_get_sync(cmdq->mbox.dev) < 0);
+	WARN_ON(pm_runtime_get(cmdq->mbox.dev) < 0);
+	WARN_ON(clk_bulk_enable(cmdq->pdata->gce_num, cmdq->clocks));
 
 	spin_lock_irqsave(&thread->chan->lock, flags);
 	if (list_empty(&thread->task_busy_list))
@@ -507,11 +515,9 @@ static int cmdq_mbox_flush(struct mbox_chan *chan, unsigned long timeout)
 	struct cmdq_task *task, *tmp;
 	unsigned long flags;
 	u32 enable;
-	int ret;
 
-	ret = pm_runtime_get_sync(cmdq->mbox.dev);
-	if (ret < 0)
-		return ret;
+	WARN_ON(pm_runtime_get(cmdq->mbox.dev) < 0);
+	WARN_ON(clk_bulk_enable(cmdq->pdata->gce_num, cmdq->clocks));
 
 	spin_lock_irqsave(&thread->chan->lock, flags);
 	if (list_empty(&thread->task_busy_list))
-- 
2.18.0