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

[Claudiu Beznea]

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"

--
Thank you,
Claudiu