[PATCH 2/4] dmaengine: ti: cppi41: Fix register access in suspend_late

[Markus Schneider-Pargmann (TI)]

cppi41_suspend() and cppi41_resume() access registers. However the
device may be runtime suspended in which case it is not allowed to
access the registers.

On suspend do not run disable_sched() when it is runtime suspended. This
avoids accessing the registers and crashing the kernel during suspend.

Resume when runtime suspended is delayed until cppi41_runtime_resume()
is called using the variable ctx_lost. This keeps any access while the
device is runtime suspended.

Fixes: fdea2d09b997 ("dmaengine: cppi41: Add basic PM runtime support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Markus Schneider-Pargmann (TI) <msp@xxxxxxxxxxxx>
---
 drivers/dma/ti/cppi41.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/ti/cppi41.c b/drivers/dma/ti/cppi41.c
index 458d20b12462..f5a824418fe7 100644
--- a/drivers/dma/ti/cppi41.c
+++ b/drivers/dma/ti/cppi41.c
@@ -146,6 +146,9 @@ struct cppi41_dd {
 	struct list_head pending;	/* Pending queued transfers */
 	spinlock_t lock;		/* Lock for pending list */
 
+	/* Register context may have been lost during system suspend */
+	bool ctx_lost;
+
 	bool is_suspended;
 };
 
@@ -1171,7 +1174,10 @@ static int __maybe_unused cppi41_suspend(struct device *dev)
 {
 	struct cppi41_dd *cdd = dev_get_drvdata(dev);
 
-	disable_sched(cdd);
+	if (!pm_runtime_status_suspended(dev))
+		disable_sched(cdd);
+
+	cdd->ctx_lost = true;
 
 	return 0;
 }
@@ -1182,6 +1188,9 @@ static int __maybe_unused cppi41_resume(struct device *dev)
 	struct cppi41_channel *c;
 	int i;
 
+	if (pm_runtime_status_suspended(dev))
+		return 0;
+
 	for (i = 0; i < DESCS_AREAS; i++)
 		cppi_writel(cdd->descs_phys, cdd->qmgr_mem + QMGR_MEMBASE(i));
 
@@ -1196,6 +1205,8 @@ static int __maybe_unused cppi41_resume(struct device *dev)
 	cppi_writel(QMGR_SCRATCH_SIZE, cdd->qmgr_mem + QMGR_LRAM_SIZE);
 	cppi_writel(0, cdd->qmgr_mem + QMGR_LRAM1_BASE);
 
+	cdd->ctx_lost = false;
+
 	return 0;
 }
 
@@ -1217,6 +1228,9 @@ static int __maybe_unused cppi41_runtime_resume(struct device *dev)
 	struct cppi41_dd *cdd = dev_get_drvdata(dev);
 	unsigned long flags;
 
+	if (cdd->ctx_lost)
+		cppi41_resume(dev);
+
 	spin_lock_irqsave(&cdd->lock, flags);
 	cdd->is_suspended = false;
 	cppi41_run_queue(cdd);

-- 
2.55.0