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

["Ming Qian(OSS)" <ming.qian@oss.nxp.com>]

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@oss.nxp.com wrote:
>>>> From: Ming Qian <ming.qian@oss.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.

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@oss.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
>>>>