[PATCH v5 08/23] dmaengine: ste_dma40: Return IRQ_NONE without interrupt status

[Linus Walleij <linusw@kernel.org>]

d40_handle_interrupt() returns IRQ_HANDLED even when no terminal-count or
error status bit is set. If the line remains asserted without matching
status, reporting it as handled prevents the generic interrupt code from
detecting the stuck interrupt.

Track whether the handler observes any DMA40 status. Return IRQ_NONE only
when none is present, allowing the generic spurious interrupt detector to
disable a faulty status-less interrupt line.

DMA40 channels can be owned by other SoC cores. Their status still explains
why the interrupt fired, but Linux must not acknowledge it. Treat foreign
status as handled and leave its acknowledgment to the owning core, while
acknowledging and dispatching only registered Linux channels.

Fixes: 8d318a50b3d7 ("DMAENGINE: Support for ST-Ericssons DMA40 block v3")
Assisted-by: LLM
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/dma/ste_dma40.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c
index bb052d3028cc..4380f9a1b035 100644
--- a/drivers/dma/ste_dma40.c
+++ b/drivers/dma/ste_dma40.c
@@ -1807,6 +1807,7 @@ static void dma_tasklet(struct tasklet_struct *t)
 
 static irqreturn_t d40_handle_interrupt(int irq, void *data)
 {
+	irqreturn_t handled = IRQ_NONE;
 	int i;
 	u32 idx;
 	u32 row;
@@ -1840,6 +1841,12 @@ static irqreturn_t d40_handle_interrupt(int irq, void *data)
 		row = chan / BITS_PER_LONG;
 		idx = chan & (BITS_PER_LONG - 1);
 
+		/*
+		 * Status for a channel owned by another core still explains
+		 * the interrupt, but only ACK Linux-owned channels below.
+		 */
+		handled = IRQ_HANDLED;
+
 		if (il[row].offset == D40_PHY_CHAN)
 			d40c = base->lookup_phy_chans[idx];
 		else
@@ -1872,7 +1879,7 @@ static irqreturn_t d40_handle_interrupt(int irq, void *data)
 	if (ret > 0)
 		pm_runtime_put_autosuspend(base->dev);
 
-	return IRQ_HANDLED;
+	return handled;
 }
 
 static int d40_validate_conf(struct d40_chan *d40c,

-- 
2.55.0