[PATCH V2 3/3] dmaengine: zynqmp_dma: Guard IRQ handler against spurious interrupts

[Golla Nagendra <nagendra.golla@amd.com>]

Add pm_runtime_get_if_active() check in zynqmp_dma_irq_handler() to
safely handle spurious interrupts that may arrive while the device is
runtime-suspended. Without this guard, a spurious interrupt could cause
the handler to access hardware registers (ISR, IMR) with clocks gated,
potentially leading to a synchronous external abort and kernel crash.

When the device is not runtime-active, pm_runtime_get_if_active()
returns false without incrementing the usage counter, and the handler
returns IRQ_NONE immediately. When the device is active, it increments
the usage counter to prevent a concurrent runtime suspend during
register access, and pm_runtime_put() releases the reference afterward.

Signed-off-by: Golla Nagendra <nagendra.golla@amd.com>
---
 drivers/dma/xilinx/zynqmp_dma.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/dma/xilinx/zynqmp_dma.c b/drivers/dma/xilinx/zynqmp_dma.c
index a9dfec3c0ca3..ce9163138be7 100644
--- a/drivers/dma/xilinx/zynqmp_dma.c
+++ b/drivers/dma/xilinx/zynqmp_dma.c
@@ -730,6 +730,9 @@ static irqreturn_t zynqmp_dma_irq_handler(int irq, void *data)
 	u32 isr, imr, status;
 	irqreturn_t ret = IRQ_NONE;
 
+	if (pm_runtime_get_if_active(chan->dev) <= 0)
+		return IRQ_NONE;
+
 	isr = readl(chan->regs + ZYNQMP_DMA_ISR);
 	imr = readl(chan->regs + ZYNQMP_DMA_IMR);
 	status = isr & ~imr;
@@ -756,6 +759,8 @@ static irqreturn_t zynqmp_dma_irq_handler(int irq, void *data)
 		ret = IRQ_HANDLED;
 	}
 
+	pm_runtime_put(chan->dev);
+
 	return ret;
 }
 
-- 
2.34.1