Re: [PATCH RESEND] dmaengine: qcom: bam_dma: Defer IRQ trigger type to device tree

[Vishnu Santhosh <vishnu.santhosh@oss.qualcomm.com>]

On 15-09-2026 07:36 pm, Frank Li wrote:
> On Fri, Jul 17, 2026 at 10:30:28AM +0530, Vishnu Santhosh wrote:
>> The driver hardcodes IRQF_TRIGGER_HIGH when registering the BAM
>> interrupt, which overrides the trigger type specified in the device
>> tree. On Qualcomm Shikra SoC, the A2 BAM signals an edge interrupt
>> to the apps processor; registering it as level-high causes the
>> interrupt to not fire, resulting in missed DMA completions.
>>
>> Use IRQF_TRIGGER_NONE instead, which causes the kernel to use the
>> trigger type already configured by platform_get_irq() when it parsed
>> the device tree interrupts property. This makes the driver
>> platform-agnostic.
> where show this? can you point me doc or code?
>
> Frank

Hi Frank,

The BAM driver obtains the IRQ through platform_get_irq():

bdev->irq = platform_get_irq(pdev, 0);

in https://elixir.bootlin.com/linux/v7.3-rc3/source/drivers/dma/qcom/bam_dma.c#L1270

It then registers the same IRQ with:

ret = devm_request_irq(bdev->dev, bdev->irq, bam_dma_irq,
                          IRQF_TRIGGER_HIGH, "bam_dma", bdev);

in https://elixir.bootlin.com/linux/v7.3-rc3/source/drivers/dma/qcom/bam_dma.c#L1335

The comment above IRQF_TRIGGER_NONE in include/linux/interrupt.h
states that when no trigger flag is specified, the interrupt uses the trigger type already
configured by the machine or firmware.

https://elixir.bootlin.com/linux/v7.3-rc3/source/include/linux/interrupt.h#L25

Therefore, IRQF_TRIGGER_HIGH overrides the trigger type associated with the IRQ during
DT/IRQ-domain mapping, while IRQF_TRIGGER_NONE preserves it.

The Shikra DTS which is still under review describes the BAM interrupt as edge-triggered:

interrupts = <GIC_SPI 74 IRQ_TYPE_EDGE_RISING 0>;

This driver change is needed so that the DT-specified trigger type remains effective once
the Shikra DTS change is accepted.


Thanks,
Vishnu


>
>> Fixes: e7c0fe2a5c84 ("dmaengine: add Qualcomm BAM dma driver")
>> Co-developed-by: Deepak Kumar Singh <deepak.singh@oss.qualcomm.com>
>> Signed-off-by: Deepak Kumar Singh <deepak.singh@oss.qualcomm.com>
>> Signed-off-by: Vishnu Santhosh <vishnu.santhosh@oss.qualcomm.com>
>> ---
>>   drivers/dma/qcom/bam_dma.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
>> index 19116295f8325767a0d97a7848077885b118241c..6c3e2ca8a572fd04c925de0adbd5cc0616b361ef 100644
>> --- a/drivers/dma/qcom/bam_dma.c
>> +++ b/drivers/dma/qcom/bam_dma.c
>> @@ -1303,7 +1303,7 @@ static int bam_dma_probe(struct platform_device *pdev)
>>   		bam_channel_init(bdev, &bdev->channels[i], i);
>>
>>   	ret = devm_request_irq(bdev->dev, bdev->irq, bam_dma_irq,
>> -			IRQF_TRIGGER_HIGH, "bam_dma", bdev);
>> +			IRQF_TRIGGER_NONE, "bam_dma", bdev);
>>   	if (ret)
>>   		goto err_bam_channel_exit;
>>
>>
>> ---
>> base-commit: e43ffb69e0438cddd72aaa30898b4dc446f664f8
>> change-id: 20260601-qcom-bam-dma-irq-trigger-0366e7e86f17
>>
>> Best regards,
>> --
>> Vishnu Santhosh <vishnu.santhosh@oss.qualcomm.com>
>>