[PATCH v3 05/22] dmaengine: ste_dma40: Check runtime PM in IRQ

[Linus Walleij <linusw@kernel.org>]

d40_handle_interrupt() reads DMA40 interrupt registers unconditionally. A
spurious interrupt can arrive while the device is runtime suspended, after
dma40_runtime_suspend() has disabled the GCC clock.

Avoid touching the registers unless the device is runtime active by taking
a conditional runtime PM reference. Return IRQ_NONE when the device is
suspended, and drop the reference after handling an active interrupt.

When CONFIG_PM is disabled, pm_runtime_get_if_active() returns -EINVAL even
though the registers remain accessible. Keep handling interrupts in that
configuration and only drop the runtime PM reference when one was acquired.

Fixes: 7fb3e75e1833 ("dmaengine/ste_dma40: support pm in dma40")
Reported-by: sashiko-bot@kernel.org
Closes: https://lore.kernel.org/dmaengine/20260819225114.AE1511F000E9@smtp.kernel.org/
Assisted-by: LLM
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/dma/ste_dma40.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c
index 28fcd196d95b..1baee6f4d919 100644
--- a/drivers/dma/ste_dma40.c
+++ b/drivers/dma/ste_dma40.c
@@ -1688,6 +1688,11 @@ static irqreturn_t d40_handle_interrupt(int irq, void *data)
 	u32 *regs = base->regs_interrupt;
 	struct d40_interrupt_lookup *il = base->gen_dmac.il;
 	u32 il_size = base->gen_dmac.il_size;
+	int ret;
+
+	ret = pm_runtime_get_if_active(base->dev);
+	if (IS_ENABLED(CONFIG_PM) && ret <= 0)
+		return IRQ_NONE;
 
 	spin_lock(&base->interrupt_lock);
 
@@ -1736,6 +1741,9 @@ static irqreturn_t d40_handle_interrupt(int irq, void *data)
 
 	spin_unlock(&base->interrupt_lock);
 
+	if (ret > 0)
+		pm_runtime_put_autosuspend(base->dev);
+
 	return IRQ_HANDLED;
 }
 

-- 
2.55.0