Re: DWC eDMA weirdness

On Thu, Jul 30, 2026 at 12:43:20PM +0200, Niklas Cassel wrote:
> On Thu, Jul 30, 2026 at 05:39:46PM +0900, Koichiro Den wrote:
> > 
> > I was struggling to reproduce this, but I think I figured out what triggers it.
> > It happens when the 'dma' variant runs before DOORBELL_TEST, e.g. when running
> > the full test suite with no arguments, or by running '-v dma' first.
> > 
> > I think the following patch fixes it:
> > 
> > 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);
> > 
> > Could you test this?
> 
> That appears to fix my problem.

Thanks for confirming. I'll send a fix for this. Sorry for the trouble.

Best regards,
Koichiro

> 
> We have had a ton of DWC problems related to IRQs.
> IIRC, most DWC IRQs, e.g. the embedded MSI controller on the PCIe controller
> itself, works using level triggered IRQs.
> 
> However, e.g. MSIs themselves are by definition edge triggered, so there is
> a difference of how you mark the IRQ handler in the DWC driver, and how you
> configure the IRQ domain that you configure to the MSI/IRQ kernel code:
> https://patchew.org/linux/20250205151635.v2.1.Id60295bee6aacf44aa3664e702012cb4710529c3@changeid/
> 
> 
> Since this is for an IRQ within the PCIe controller, I think this is correct.
> 
> 
> 
> We've also seen problems where we've been clearing the level IRQ too
> late, see e.g.
> ca1658921b63 ("PCI: designware: Fix missing MSI IRQs")
> 
> which caused us to miss IRQs when two MSIs came very close after one another.
> 
> 
> 
> Kind regards,
> Niklas