Re: [PATCH v2 3/3] media: imx-jpeg: Check decoding is ongoing for motion-jpeg

[Ming Qian(OSS)]

Hi Sebastian,

On 2025/4/5 23:37, Sebastian Fricke wrote:
> Hey Ming,
>
> On 28.03.2025 14:30, ming.qian@xxxxxxxxxxx wrote:
> > From: Ming Qian <ming.qian@xxxxxxxxxxx>
> >
> > To support decoding motion-jpeg without DHT, driver will try to decode a
> > pattern jpeg before actual jpeg frame by use of linked descriptors
> > (This is called "repeat mode"), then the DHT in the pattern jpeg can be
> > used for decoding the motion-jpeg.
>
> Hmm do we need to repeat the description from the previous patch?

This issue is also caused by the repeat mode, I thought I should explain
it, but as you said, this does make it redundant.

> > In other words, 2 frame done interrupts will be triggered, driver will
> > ignore the first interrupt, and wait for the second interrupt.
> > If the resolution is small, and the 2 interrupts may be too close,
> > when driver is handling the first interrupt, two frames are done, then
> > driver will fail to wait for the second interrupt.
>
> Okay this first part is a bit hard to understand, how about:
>
> As the first frame in "repeat-mode" is the pattern, the first interrupt
> is ignored by the driver. With small resolution bitstreams, the
> interrupts might fire too quickly and thus the driver might miss the
> second interrupt from the first actual frame.
>
> Is that what you mean?
Yes, you're right, and it's better now.

> > In such case, driver can check whether the decoding is still ongoing,
> > if not, just done the current decoding.
>
> That doesn't answer to me why this solves the issue of missing the
> second interrupt, can you elaborate your solution a bit so that the
> reader of the commit description understands why this is needed?

When the first frame-done interrupt is received, we need to figure out
if we can get the second interrupt.
So we check the curr_desc register first,
if it is still pointing to the pattern descripor, the second actual
frame is not started, we can wait for its frame-doen interrupt.
if the curr_desc has pointed to the frame descriptor, then we check the
ongoing bit of slot_status register.
if the ongoing bit is set to 1, the decoding of the actual frame is not
finished, we can wait for its frame-doen interrupt.
if the ongoing bit is set o 0, the decoding of the actual frame is
finished, we can't wait for the second interrupt, but mark it as done.

But there is still a small problem, that the curr_desc and slot_status
registers are not synchronous. curr_desc is updated when the
next_descpt_ptr is loaded, but the ongoing bit of slot_status is set
after the 32 bytes descriptor is loaded, there will be a short time
interval in between, which may cause fake faluse. Reading slot_status
twice can basically reduce the probability of fake false to 0.

Regards,
Ming

> Regards,
> Sebastian
>
> > Signed-off-by: Ming Qian <ming.qian@xxxxxxxxxxx>
> > ---
> > .../media/platform/nxp/imx-jpeg/mxc-jpeg-hw.h |  1 +
> > .../media/platform/nxp/imx-jpeg/mxc-jpeg.c    | 20 ++++++++++++++++++-
> > 2 files changed, 20 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg-hw.h 
> > b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg-hw.h
> > index d579c804b047..adb93e977be9 100644
> > --- a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg-hw.h
> > +++ b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg-hw.h
> > @@ -89,6 +89,7 @@
> > /* SLOT_STATUS fields for slots 0..3 */
> > #define SLOT_STATUS_FRMDONE            (0x1 << 3)
> > #define SLOT_STATUS_ENC_CONFIG_ERR        (0x1 << 8)
> > +#define SLOT_STATUS_ONGOING            (0x1 << 31)
> >
> > /* SLOT_IRQ_EN fields TBD */
> >
> > diff --git a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c 
> > b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
> > index 45705c606769..e6bb45633a19 100644
> > --- a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
> > +++ b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
> > @@ -910,6 +910,23 @@ static u32 mxc_jpeg_get_plane_size(struct 
> > mxc_jpeg_q_data *q_data, u32 plane_no)
> >     return size;
> > }
> >
> > +static bool mxc_dec_is_ongoing(struct mxc_jpeg_ctx *ctx)
> > +{
> > +    struct mxc_jpeg_dev *jpeg = ctx->mxc_jpeg;
> > +    u32 curr_desc;
> > +    u32 slot_status;
> > +
> > +    slot_status = readl(jpeg->base_reg + MXC_SLOT_OFFSET(ctx->slot, 
> > SLOT_STATUS));
> > +    curr_desc = readl(jpeg->base_reg + MXC_SLOT_OFFSET(ctx->slot, 
> > SLOT_CUR_DESCPT_PTR));
> > +
> > +    if (curr_desc == jpeg->slot_data.cfg_desc_handle)
> > +        return true;
> > +    if (slot_status & SLOT_STATUS_ONGOING)
> > +        return true;
> > +
> > +    return false;
> > +}
> > +
> > static irqreturn_t mxc_jpeg_dec_irq(int irq, void *priv)
> > {
> >     struct mxc_jpeg_dev *jpeg = priv;
> > @@ -979,7 +996,8 @@ static irqreturn_t mxc_jpeg_dec_irq(int irq, void 
> > *priv)
> >         mxc_jpeg_enc_mode_go(dev, reg, 
> > mxc_jpeg_is_extended_sequential(q_data->fmt));
> >         goto job_unlock;
> >     }
> > -    if (jpeg->mode == MXC_JPEG_DECODE && jpeg_src_buf->dht_needed) {
> > +    if (jpeg->mode == MXC_JPEG_DECODE && jpeg_src_buf->dht_needed &&
> > +        mxc_dec_is_ongoing(ctx)) {
> >         jpeg_src_buf->dht_needed = false;
> >         dev_dbg(dev, "Decoder DHT cfg finished. Start decoding...\n");
> >         goto job_unlock;
> > --
> > 2.43.0-rc1