RE: [PATCH v6 01/18] dmaengine: sh: rz-dmac: Move interrupt request after everything is set up

[Biju Das]

> -----Original Message-----
> From: Claudiu Beznea <claudiu.beznea@xxxxxxxxxx>
> Sent: 26 May 2026 11:26
> Subject: Re: [PATCH v6 01/18] dmaengine: sh: rz-dmac: Move interrupt request after everything is set
> up
> 
> 
> 
> On 5/26/26 12:51, Biju Das wrote:
> > Hi Claudiu,
> >
> >> -----Original Message-----
> >> From: Claudiu Beznea <claudiu.beznea@xxxxxxxxxx>
> >> Sent: 26 May 2026 10:46
> >> Subject: Re: [PATCH v6 01/18] dmaengine: sh: rz-dmac: Move interrupt
> >> request after everything is set up
> >>
> >>
> >>
> >> On 5/26/26 11:54, Biju Das wrote:
> >>> Hi Claudiu,
> >>>
> >>>> -----Original Message-----
> >>>> From: Claudiu Beznea <claudiu.beznea@xxxxxxxxxx>
> >>>> Sent: 26 May 2026 09:47
> >>>> Subject: [PATCH v6 01/18] dmaengine: sh: rz-dmac: Move interrupt
> >>>> request after everything is set up
> >>>>
> >>>> From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
> >>>>
> >>>> Once the interrupt is requested, the interrupt handler may run immediately.
> >>>
> >>> Do you mean spurious interrupt?
> >>>
> >>> After DMA driver probe only, consumer device can access the DMA
> >>> handle right? or am I missing something here?
> >>
> >> In theory there could be pending interrupts not yet served (e.g. due
> >> to the previous usage of the controller, HW behavior, etc). Those
> >> could trigger the execution of the IRQ handler once the interrupt is requested.
> >
> > You mean DMA consumers configured by bootloader and linux probing the
> > DMA driver can trigger IRQ?
> DMA used by bootloaders may be a valid scenario, even though may not currently be used in the setups
> this IP is used.
> 
> Please check the documentation of request_threaded_irq():
> https://elixir.bootlin.com/linux/v7.1-rc4/source/kernel/irq/manage.c#L2089
> 
> "* ... From the point this call is made your handler function
>   * may be invoked. Since your handler function must clear any interrupt the
>   * board raises, you must take care both to initialise your hardware and to
>   * set up the interrupt handler in the right order"

OK. Then it make sense as the bootloader/board may have some register
configured for triggering IRQ and it will lead to crash..

Cheers,
Biju