Re: [PATCH v4 1/3] dt-bindings: dma: arm-dma350: document generic and combined IRQ topologies

[Jun Guo]

On 3/24/2026 8:04 PM, Robin Murphy wrote:
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> On 2026-03-23 11:48 am, Jun Guo wrote:
> > Update the DMA-350 DT binding to match the current driver behavior.
> >
> > Allow both:
> > - "arm,dma-350" as the generic compatible, and
> > - "cix,sky1-dma-350", "arm,dma-350" for SoC-specific fallback usage.
> >
> > Also document interrupt topology variants supported by hardware
> > integration:
> > - one combined interrupt for all channels, or
> > - one interrupt per channel (up to 8 channels).
>
> To repeat myself for the 3rd time, this is at best unnecessary, and at
> worst arguably wrong. Here's an example of a system which happens to use
> the combined interrupt from another IP block which also offers both 
> options:
>
> https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ 
> tree/arch/arm64/boot/dts/freescale/imx8qm.dtsi#n279
>
> Same thing here; each channel is a distinct interrupt source, so it is
> perfectly honest to describe that consistently in DT, regardless of
> whether or not the interrupt signals are still distinct by the time they
> reach the interrupt controller.
>
> Furthermore, in this case the IRQ_COMB_NONSEC interrupt actually has
> additional functionality beyond just being a mux of the individual
> IRQ_CHANNEL interrupts. So although Linux probably won't ever care, if
> it's going to be in the DT binding then it should really be distinct
> from the channel interrupts anyway, since systems could well wire them
> *all* up, and an OS could choose to use the IRQ_CHANNEL outputs directly
> for individual channel completion/error status, while also using the
> IRQ_COMB_NONSEC just for its overall INTR_ALLCH{STOPPED,PAUSED,IDLE} 
> status.
>
> If you only want to make your thing work in Linux, all that is needed is
> a 1-line change in the driver to enable the INTR_ANYCHINTR bit (which as
> I've also said before, we can do unconditionally because we're *not*
> using the other INTR_ALLCH stuff), and to write your DT using the
> existing binding. "One interrupt per channel" already carries no
> expectation that they all have to be *different* interrupts.
You've indeed said this for the third time, but I did not ignore your
comments earlier. I carefully reviewed your feedback on both the V1
and V2 patches. However, since your initial comments were not as detailed,
I promptly replied to your emails hoping to discuss them further.
Unfortunately, you did not respond to either of my follow-up emails,
so I proceeded with submitting the current version of the patch.

You can refer to the records here:
https://lore.kernel.org/all/20251216123026.3519923-2-jun.guo@xxxxxxxxxxx/
or
https://lore.kernel.org/all/20251117015943.2858-3-jun.guo@xxxxxxxxxxx/

Now, with this latest email, I clearly understand the point you are making.
I will revise and resubmit the patch accordingly, which should result in
a much more concise version. Thank you for your reply.

Best regards,
Jun