linux-kernel - Re: [PATCH v1 5/6] media: rkisp1: Give buffers back instead of dropping in bypass mode

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Message-ID: <177022300744.3835511.13262707370784191079@isaac-ThinkPad-T16-Gen-2>
Date: Wed, 04 Feb 2026 16:36:47 +0000
From: Isaac Scott <isaac.scott@...asonboard.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: linux-media@...r.kernel.org, dafna@...tmail.com, mchehab@...nel.org, heiko@...ech.de, linux-rockchip@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 5/6] media: rkisp1: Give buffers back instead of dropping in bypass mode

Hi Laurent,

Quoting Laurent Pinchart (2026-02-04 15:40:04)
> On Wed, Feb 04, 2026 at 11:25:05AM +0000, Isaac Scott wrote:
> > In the data mode used for YUV passthrough, falling VSYNC events are used
> > to determine when a buffer is complete. This means there is no 'Frame
> > End' signal.
> > 
> > Previously, all buffers would be dropped when bypass mode was active.
> > Instead of dropping every frame, we should return the buffer to user
> > space if it is marked as complete by a falling VSYNC signal.
> > 
> > Signed-off-by: Isaac Scott <isaac.scott@...asonboard.com>
> > ---
> >  drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c b/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
> > index 867cdddf9f89..2753be39ab33 100644
> > --- a/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
> > +++ b/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
> > @@ -832,6 +832,11 @@ irqreturn_t rkisp1_capture_isr(int irq, void *ctx)
> >       for (i = 0; i < dev_count; ++i) {
> >               struct rkisp1_capture *cap = &rkisp1->capture_devs[i];
> >  
> > +             if (rkisp1->in_bypass) {
> > +                     rkisp1_handle_buffer(cap);
> > +                     continue;
> > +             }
> > +
> 
> You're completing the buffer if *any* interrupt bit is set, this doesn't
> seem right. At the moment we may not enable interrupts other than the
> one you expect, but that may change later, and this will misbehave.
> You're also not handling the stopping logic, which also seems wrong.
> 
> Finally, what interrupt bit do you expect to see ? There's no VSYNC
> interrupt in the RKISP1_CIF_MI_MIS register. Are you relying on the fact
> that your platform has a single interrupt line for the three interrupt
> sources (CSI2, ISP and MI), and react to the VSYNC interrupt from the
> ISP interrupt here ? That's not right either, not only will it not work
> on platforms that have three separate interrupt lines, but it will also
> cause rkisp1_handle_buffer() to be called for *any* ISP interrupt.
> 
> I'm surprised that the frame end interrupt doesn't fire. It's part of
> the MI, not the ISP, so it shouldn't be affected by bypass mode. You
> should investigate that.

You're right, I think I should get a frame end interrupt. I think what
has happened is during development part I was getting no frame end
interrupts, so I made this change, but it actually turned out to be an
inform_size_err if I recall correctly.

Although it may also be incorrect, I have checked whether I actually do
not get a frame end interrupt by dropping this patch, and it seems I do.
(I must have had my FPGA configured to output the wrong width / height
at the time).

I'll drop this in v2 as it doesn't seem necessary.

Thanks very much,
Isaac

> 
> >               if (!(status & RKISP1_CIF_MI_FRAME(cap)))
> >                       continue;
> >               if (!cap->is_stopping) {
> 
> -- 
> Regards,
> 
> Laurent Pinchart