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

[Claudiu Beznea <claudiu.beznea@kernel.org>]

On 5/26/26 12:51, Biju Das wrote:
> Hi Claudiu,
> 
>> -----Original Message-----
>> From: Claudiu Beznea <claudiu.beznea@kernel.org>
>> 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@kernel.org>
>>>> 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@bp.renesas.com>
>>>>
>>>> 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