Message-ID: <Z+v6Q1TRpJUkF2oh@lizhi-Precision-Tower-5810>
Date: Tue, 1 Apr 2025 10:37:55 -0400
From: Frank Li <Frank.li@....com>
To: "Ming Qian(OSS)" <ming.qian@....nxp.com>
Cc: mchehab@...nel.org, hverkuil-cisco@...all.nl,
	mirela.rabulea@....nxp.com, shawnguo@...nel.org,
	s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
	xiahong.bao@....com, eagle.zhou@....com, linux-imx@....com,
	imx@...ts.linux.dev, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 3/3] media: imx-jpeg: Check decoding is ongoing for
 motion-jpeg

On Tue, Apr 01, 2025 at 11:17:36AM +0800, Ming Qian(OSS) wrote:
>
> Hi Frank,
>
> On 2025/3/31 22:32, Frank Li wrote:
> > On Mon, Mar 31, 2025 at 11:10:20AM +0800, Ming Qian(OSS) wrote:
> > >
> > > Hi Frank,
> > >
> > > On 2025/3/28 22:45, Frank Li wrote:
> > > > On Fri, Mar 28, 2025 at 02:30:52PM +0800, ming.qian@....nxp.com wrote:
> > > > > From: Ming Qian <ming.qian@....nxp.com>
> > > > >
> > > > > 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.
> > > > >
> > > > > In other words, 2 frame done interrupts will be triggered, driver will
> > > > > ignore the first interrupt,
> > > >
> > > > Does any field in linked descriptors to control if issue irq? Generally
> > > > you needn't enable first descriptors's irq and only enable second one.
> > > >
> > >
> > > Unfortunately, we cannot configure interrupts for each descriptor.
> > > So we can't only enable the second irq.
> > >
> > >
> > > > > and wait for the second interrupt.
> > > > > If the resolution is small, and the 2 interrupts may be too close,
> > > >
> > > > It also possible two irqs combine to 1 irqs. If I understand correct, your
> > > > irq handle only handle one descriptors per irq.
> > > >
> > > > Another words,
> > > >
> > > > If second irq already happen just before 1,
> > > >
> > > > 1. dec_ret = readl(reg + MXC_SLOT_OFFSET(slot, SLOT_STATUS));
> > > > 2. writel(dec_ret, reg + MXC_SLOT_OFFSET(slot, SLOT_STATUS)); /* w1c */
> > > >
> > > > Does your driver wait forever because no second irq happen?
> > > >
> > > > Frank
> > >
> > > Before this patch, the answer is yes, the driver will wait 2 seconds
> > > until timeout.
> > > In fact, this is the problem that this patch wants to avoid.
> > > Now I think there are 3 cases for motion-jpeg decoding:
> > > 1. The second irq happens before the first irq status check, the on-going
> > > check
> > > help to hanle this case.
> > > 2. The second irq happens after the first irq status check, but before
> > > on-going check, this on-going check can help handle it, fisnish the
> > > current decoding and reset the jpeg decoder.
> > > 3. The second irq happens after the on-going check, this is the normal
> > > process before. No additional processing required.
> >
> > Okay, not sure if hardware provide current_descript position. Generally
> > descriptor queue irq handle is like
> >
> > cur = queue_header;
> > while(cur != read_hardware_currunt_pos())
> > {
> > 	handle(cur);
> > 	cur = cur->next;
> > 	queue_header = cur;
> > }
> >
> > with above logic, even you queue new request during irq handler, it should
> > work correctly.
> >
> > But it is depend on if hardware can indicate current working queue
> > position, some time, hardware stop last queue posistion when handle last
> > one.
> >
> > Frank
> >
>
> I think it doesn't matter, the 2 descriptors are the cfg descriptor and
> then the image descriptor.
> If the current descriptor register remains the last image descriptor,
> the ongoing check works.
>
> And I guess your concern is as below.
> If the current descriptor register is still the cfg descriptor, but the
> hardware has finished decoding the next image descriptor.
>
> I confirmed with our hardware engineer. This can't happen.
> The first cfg decriptor has a next_descpt_ptr that is pointing to the
> image descriptor, when the hardware read tne next_descpt_ptr, the
> current descriptor register is updated, before the actual decoding.

Maybe off topic,

CFG->next = Image

Image->next = NULL;

If hardware finish image descriptior, current descriptor is 'Image' or 'NULL'

If it is 'Image', need extra status bit show 'done'

1:	slot_status = readl(jpeg->base_reg + MXC_SLOT_OFFSET(ctx->slot, SLOT_STATUS));

I suppose it should be DONE status if just finish CFG description.

2: 	curr_desc = readl(jpeg->base_reg + MXC_SLOT_OFFSET(ctx->slot, SLOT_CUR_DESCPT_PTR));

It is possible curr_desc already was 'Image' after 1.

 if (curr_desc == jpeg->slot_data.cfg_desc_handle)  //not hit this
        return true;

 if (slot_status & SLOT_STATUS_ONGOING)  // not hit this
        return true;

fake false may return.

check two aync condition "slot_status" and "curr_desc" always be risk. But
I don't know what's happen if fake false return here.

for this type check
	do {
		slot_status = readl();
		curr_desc = readl();
	} while (slot_status != read());

to make sure slot_status and cur_desc indicate the hardware status
correctly.

Frank
>
> Thanks,
> Ming
>
> > >
> > > Thanks,
> > > Ming
> > >
> > > > >
> > > > > when driver is handling the first interrupt, two frames are done, then
> > > > > driver will fail to wait for the second interrupt.
> > > > >
> > > > > In such case, driver can check whether the decoding is still ongoing,
> > > > > if not, just done the current decoding.
> > > > >
> > > > > Signed-off-by: Ming Qian <ming.qian@....nxp.com>
> > > > > ---
> > > > >    .../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
> > > > >

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