Re: [PATCH 05/14] media: qcom: camss: csid-gen3: Enable RDI SOF driving

[Bryan O'Donoghue <bryan.odonoghue@linaro.org>]

On 29/10/2026 15:43, Loic Poulain wrote:
>>                          __csid_configure_rx(csid, &csid->phy, 0);
>> +                       __csid_configure_rdi_irq(csid, enable, i);
> Is this something that should also be tied to frame_sync_en?
> 
> Also, just thinking out loud, are there cases where we'd want to
> toggle this dynamically at runtime based on any V4L2 configuration or
> pipeline path? For example, should it be enabled for the pixel path
> but disabled for RDI?
> 
> I'm asking because one of the appreciated strengths of CAMSS is its
> relatively low-latency and lightweight capture path. As we add more
> features, it may be worth preserving that characteristic where
> possible. Not saying this particular feature has a meaningful latency
> or compute cost, but more as a general design consideration.
> 
> Regards,
> Loic
> 
>>                          __csid_ctrl_rdi(csid, enable, i);
>>                  }
>>   }
>> @@ -279,6 +303,9 @@ static irqreturn_t csid_isr(int irq, void *dev)
>>                          val = readl(csid->base + CSID_CSI2_RDIN_IRQ_STATUS(i));
>>                          writel(val, csid->base + CSID_CSI2_RDIN_IRQ_CLEAR(i));
>>
>> +                       if (val & INFO_INPUT_SOF_IRQ)
>> +                               csid_sof_event(csid, i);

I considered dynamic enable but

1. The design here is to move ~ everything to SOF vb.sequence
2. Standard design pattern with FRAME_SYNC is to generate the event
    having consumers either trigger on it or not

For that second case I opted to only send the signal when we know 
there's a consumer though

=>

+	if (atomic_read(&csid->frame_sync_users[id]))
+		v4l2_event_queue(csid->subdev.devnode, &event);

---
bod