Hi Laurent, Vishal,
On 19/04/20 20:02, Laurent Pinchart wrote:
[...]
>> +static irqreturn_t xcsi2rxss_irq_handler(int irq, void *dev_id)
>> +{
>> + struct xcsi2rxss_state *state = (struct xcsi2rxss_state *)dev_id;
>> + struct xcsi2rxss_core *core = &state->core;
>> + u32 status;
>> +
>> + status = xcsi2rxss_read(core, XCSI_ISR_OFFSET) & XCSI_ISR_ALLINTR_MASK;
>> + dev_dbg_ratelimited(core->dev, "interrupt status = 0x%08x\n", status);
>
> As this is expected to occur for every frame, I would drop the message,
> even if rate-limited.
>
>> +
>> + if (!status)
>> + return IRQ_NONE;
>> +
>> + /* Received a short packet */
>> + if (status & XCSI_ISR_SPFIFONE) {
>> + dev_dbg_ratelimited(core->dev, "Short packet = 0x%08x\n",
>> + xcsi2rxss_read(core, XCSI_SPKTR_OFFSET));
>> + }
>
> Same here, this will occur all the time, I'd remove this message. You
> need to read XCSI_SPKTR_OFFSET though, and you should do so in a loop
> until the XCSI_CSR_SPFIFONE in XCSI_CSR_OFFSET is cleared in case
> multiple short packets are received before the interrupt handler
> executes.
>
> I also wonder if it would make sense to extract the frame number from
> the FS short packet, and make it available through the subdev API. I
> think it should be reported through a V4L2_EVENT_FRAME_SYNC event. This
> can be implemented later.
>
>> +
>> + /* Short packet FIFO overflow */
>> + if (status & XCSI_ISR_SPFIFOF)
>> + dev_dbg_ratelimited(core->dev, "Short packet FIFO overflowed\n");
>> +
>> + /*
>> + * Stream line buffer full
>> + * This means there is a backpressure from downstream IP
>> + */
>> + if (status & XCSI_ISR_SLBF) {
>> + dev_alert_ratelimited(core->dev, "Stream Line Buffer Full!\n");
>> + xcsi2rxss_stop_stream(state);
>> + if (core->rst_gpio) {
>> + gpiod_set_value(core->rst_gpio, 1);
>> + /* minimum 40 dphy_clk_200M cycles */
>> + ndelay(250);
>> + gpiod_set_value(core->rst_gpio, 0);
>> + }
>
> I don't think you should stop the core here. xcsi2rxss_stop_stream()
> calls the source .s_stream(0) operation, which usually involves I2C
> writes that will sleep.
>
> You should instead report an event to userspace (it looks like we have
> no error event defined in V4L2, one should be added), and rely on the
> normal stop procedure.
FWIW, since a long time I've been using a modified version of this
routine, where after a Stream Line Buffer Full condition I just stop and
restart the csi2rx core and the stream continues after a minimal glitch.
Other subdev are unaware that anything has happened and keep on streaming.
Not sure this is the correct thing to do, but it's working for me. Also
I proposed this topic in one of the previous iterations of this patch,
but the situation was different because the stream on/off was not
propagated back at that time.
--
Luca
