Re: [PATCH v3 06/12] media: staging: rkisp1: remove atomic operations for frame sequence

[Tomasz Figa <tfiga@chromium.org>]

Hi Helen,

On Fri, Nov 6, 2020 at 11:43 PM Helen Koike <helen.koike@collabora.com> wrote:
>
> Hi Tomasz,
>
> (sorry for not had replied this earlier)
>
> On 10/2/20 12:30 PM, Tomasz Figa wrote:
> > On Fri, Oct 2, 2020 at 11:16 AM Dafna Hirschfeld
> > <dafna.hirschfeld@collabora.com> wrote:
> >>
> >> Hi,
> >>
> >> Am 25.09.20 um 22:42 schrieb Tomasz Figa:
> >>> Hi Dafna,
> >>>
> >>> On Tue, Sep 22, 2020 at 01:33:56PM +0200, Dafna Hirschfeld wrote:
> >>>> The isp.frame_sequence is now read only from the irq handlers
> >>>> that are all fired from the same interrupt, so there is not need
> >>>> for atomic operation.
> >>>> In addition, the frame seq incrementation is moved from
> >>>> rkisp1_isp_queue_event_sof to rkisp1_isp_isr to make the code
> >>>> clearer and the incorrect inline comment is removed.
> >>>>
> >>>> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
> >>>> Acked-by: Helen Koike <helen.koike@collabora.com>
> >>>>
> >>>> ---
> >>>> changes since v2:
> >>>> add a closing "}" to if condition
> >>>> remove usless inline comment
> >>>> ---
> >>>>   drivers/staging/media/rkisp1/rkisp1-capture.c |  2 +-
> >>>>   drivers/staging/media/rkisp1/rkisp1-common.h  |  2 +-
> >>>>   drivers/staging/media/rkisp1/rkisp1-isp.c     | 16 +++++-----------
> >>>>   drivers/staging/media/rkisp1/rkisp1-params.c  |  2 +-
> >>>>   drivers/staging/media/rkisp1/rkisp1-stats.c   |  3 +--
> >>>>   5 files changed, 9 insertions(+), 16 deletions(-)
> >>>>
> >>>
> >>> Thank you for the patch. Please see my comments inline.
> >>>
> >>>> diff --git a/drivers/staging/media/rkisp1/rkisp1-capture.c b/drivers/staging/media/rkisp1/rkisp1-capture.c
> >>>> index 0632582a95b4..1c762a369b63 100644
> >>>> --- a/drivers/staging/media/rkisp1/rkisp1-capture.c
> >>>> +++ b/drivers/staging/media/rkisp1/rkisp1-capture.c
> >>>> @@ -632,7 +632,7 @@ static void rkisp1_handle_buffer(struct rkisp1_capture *cap)
> >>>>      curr_buf = cap->buf.curr;
> >>>>
> >>>>      if (curr_buf) {
> >>>> -            curr_buf->vb.sequence = atomic_read(&isp->frame_sequence);
> >>>> +            curr_buf->vb.sequence = isp->frame_sequence;
> >>>
> >>> I wonder if with higher resolutions, let's say full 5 Mpix, and/or some
> >>> memory-intensive system load, like video encoding and graphics rendering,
> >>> the DMA wouldn't take enough time to have the MI_FRAME interrupt fire after
> >>> the V_START for the next frame.
> >>>
> >>> I recall you did some testing back in time [1], showing that the two are
> >>> interleaved. Do you remember what CAPTURE resolution was it?
> >>
> >> I ran the testing again, I added a patch to allow streaming simultanously from
> >> both pathes: https://gitlab.collabora.com/dafna/linux/-/commit/8df0d15567b27cb88674fbbe33d1906c3c5a91da
> >> Then I ran two tests:
> >> stream simultaneously with 3280x2464 frames from the camera, and then downscaling them to 1920x1080 on selfpath, this is http://ix.io/2zoP
> >> stream simultaneously with 640x480 frames from the camera, and upscaling them to 1920x1080 on the selfpath. this is http://ix.io/2zoR
> >>
> >> the pixelformat for both is 422P.
> >> I don't know how meaningful and useful is to test it on the rockchip-pi4 board, I only use it with a serial console.
> >> The functionality can probably only be tested on the scarlet.
> >
> > Okay, thanks. It looks like there is always plenty of time margin on
> > the hardware side and if the interrupt handling is delayed for a short
> > time and both are handled by the same handler call, it's also going to
> > be handled fine because of rkisp1_capture_isr() being called before
> > rkisp1_isp_isr().
> >
> > By the way, do we need the MIPI interrupts every frame? Perhaps we
> > could enable the RKISP1_CIF_MIPI_ERR_CTRL* interrupts only and then,
> > when we get an error, we disable it and enable
> > RKISP1_CIF_MIPI_FRAME_END, which would then re-enable
> > RKISP1_CIF_MIPI_ERR_CTRL* and disable itself? WDYT?
>
> The driver already do this in a sense, it disables these interrupts on
> the first MIPI error and re-enable them on RKISP1_CIF_MIPI_FRAME_END.

Yes, it disables the ERR interrupts, but doesn't it keep the FRAME_END
interrupt enabled all the time? (At least that seems to be the case in
your traces.) Is it necessary?

Best regards,
Tomasz

>
> Please check:
>
> https://git.linuxtv.org/media_tree.git/tree/drivers/staging/media/rkisp1/rkisp1-isp.c#n1069
>
> For convenience:
>
> void rkisp1_mipi_isr(struct rkisp1_device *rkisp1)
> {
>         u32 val, status;
>
>         status = rkisp1_read(rkisp1, RKISP1_CIF_MIPI_MIS);
>         if (!status)
>                 return;
>
>         rkisp1_write(rkisp1, status, RKISP1_CIF_MIPI_ICR);
>
>         /*
>          * Disable DPHY errctrl interrupt, because this dphy
>          * erctrl signal is asserted until the next changes
>          * of line state. This time is may be too long and cpu
>          * is hold in this interrupt.
>          */
>         if (status & RKISP1_CIF_MIPI_ERR_CTRL(0x0f)) {
>                 val = rkisp1_read(rkisp1, RKISP1_CIF_MIPI_IMSC);
>                 rkisp1_write(rkisp1, val & ~RKISP1_CIF_MIPI_ERR_CTRL(0x0f),
>                              RKISP1_CIF_MIPI_IMSC);
>                 rkisp1->isp.is_dphy_errctrl_disabled = true;
>         }
>
>         /*
>          * Enable DPHY errctrl interrupt again, if mipi have receive
>          * the whole frame without any error.
>          */
>         if (status == RKISP1_CIF_MIPI_FRAME_END) {
>                 /*
>                  * Enable DPHY errctrl interrupt again, if mipi have receive
>                  * the whole frame without any error.
>                  */
>                 if (rkisp1->isp.is_dphy_errctrl_disabled) {
>                         val = rkisp1_read(rkisp1, RKISP1_CIF_MIPI_IMSC);
>                         val |= RKISP1_CIF_MIPI_ERR_CTRL(0x0f);
>                         rkisp1_write(rkisp1, val, RKISP1_CIF_MIPI_IMSC);
>                         rkisp1->isp.is_dphy_errctrl_disabled = false;
>                 }
>         } else {
>                 rkisp1->debug.mipi_error++;
>         }
> }
>
> Regards,
> Helen
>
> >
> > Best regards,
> > Tomasz
> >
> >>
> >> Thanks,
> >> Dafna
> >>
> >>
> >>
> >>>
> >>>>              curr_buf->vb.vb2_buf.timestamp = ktime_get_boottime_ns();
> >>>>              curr_buf->vb.field = V4L2_FIELD_NONE;
> >>>>              vb2_buffer_done(&curr_buf->vb.vb2_buf, VB2_BUF_STATE_DONE);
> >>>> diff --git a/drivers/staging/media/rkisp1/rkisp1-common.h b/drivers/staging/media/rkisp1/rkisp1-common.h
> >>>> index 232bee92d0eb..51c92a251ea5 100644
> >>>> --- a/drivers/staging/media/rkisp1/rkisp1-common.h
> >>>> +++ b/drivers/staging/media/rkisp1/rkisp1-common.h
> >>>> @@ -131,7 +131,7 @@ struct rkisp1_isp {
> >>>>      const struct rkisp1_isp_mbus_info *src_fmt;
> >>>>      struct mutex ops_lock; /* serialize the subdevice ops */
> >>>>      bool is_dphy_errctrl_disabled;
> >>>> -    atomic_t frame_sequence;
> >>>> +    __u32 frame_sequence;
> >>>
> >>> nit: The __ prefixed types are defined for the UAPI to avoid covering userspace
> >>> types. For kernel types please just use the plain u32.
> >>>
> >>> Best regards,
> >>> Tomasz
> >>>
> >