[PATCH] dmaengine: dw-edma: Mark emulated IRQ as level-triggered

[Koichiro Den]

The interrupt-emulation virtual IRQ uses handle_level_irq(), but the IRQ
descriptor has not been marked with IRQ_LEVEL.

The interrupt emulation is somewhat unusual: the eDMA interrupt handlers
dispatch the virtual IRQ for every edma_int[] interrupt because software
cannot reliably tell an interrupt-emulation event from one caused solely
by DONE/ABORT status. If an interrupt arrives before the doorbell
handler is registered for the virtual IRQ, the IRQ core marks it
pending. When the IRQ is later started, check_irq_resend() treats it as
non-level and replays the pending interrupt, causing the newly
registered handler to run for a stale event.

Mark the virtual IRQ with IRQ_LEVEL so the stale pending state is
cleared without being replayed. This was observed in pci_endpoint_test
as two doorbell handler calls when the DMA-variant test ran before
DOORBELL_TEST.

Fixes: d9d5e1bdd180 ("dmaengine: dw-edma: Add virtual IRQ for interrupt-emulation doorbells")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Niklas Cassel <cassel@xxxxxxxxxx>
Closes: https://lore.kernel.org/r/ampndLtU32ODmncX@ryzen
Tested-by: Niklas Cassel <cassel@xxxxxxxxxx>
Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
---
 drivers/dma/dw-edma/dw-edma-core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index 89a4c498a17b..ec097c68cf5f 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -755,6 +755,7 @@ static int dw_edma_emul_irq_alloc(struct dw_edma *dw)
 		return virq;
 
 	irq_set_chip_and_handler(virq, &dw_edma_emul_irqchip, handle_level_irq);
+	irq_set_status_flags(virq, IRQ_LEVEL);
 	irq_set_chip_data(virq, dw);
 	irq_set_noprobe(virq);
 

base-commit: f5098b6bae761e346ebcd9da7f95622c04733cff
-- 
2.51.0