Re: [PATCH v4 4/4] media: imx-jpeg: Check decoding is ongoing for motion-jpeg

Frank Li
2025-04-11T14:39:05Z

On Fri, Apr 11, 2025 at 03:43:43PM +0800, ming.qian@oss.nxp.com wrote:
> From: Ming Qian <ming.qian@oss.nxp.com>
>
> As the first frame in "repeat-mode" is the pattern, the pattern done
> interrupt is ignored by the driver. With small resolution bitstreams,
> the interrupts might fire too quickly and hardware combine two irqs to
> once because irq handle have latency. Thus the driver might miss the
> frame decode done interrupt from the first actual frame.
>
> In order to avoid the driver wait for the frame done interrupt that has
> been combined to the pattern done interrupt and been ignored, driver
> will check the curr_desc and slot_status registers to figure out if the
> decoding of actual frame is finished or not.
>
> Firstly we check the curr_desc register,
> - if it is still pointing to the pattern descriptor, the second actual
> frame is not started, we can wait for its frame-done 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-done interrupt.
> - if the ongoing bit is set to 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 false. Consider read register
> is quite slow compared with IP read 32byte from memory, read twice
> slot_status can avoid this situation.
>
> Signed-off-by: Ming Qian <ming.qian@oss.nxp.com>

Reviewed-by: Frank Li <Frank.Li@nxp.com>

> ---
> .../media/platform/nxp/imx-jpeg/mxc-jpeg-hw.h | 1 +
> .../media/platform/nxp/imx-jpeg/mxc-jpeg.c | 31 ++++++++++++++++++-
> 2 files changed, 31 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..4346dcdc9697 100644
> --- a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
> +++ b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
> @@ -910,6 +910,34 @@ 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;
> +
> + 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;
> +
> + slot_status = readl(jpeg->base_reg + MXC_SLOT_OFFSET(ctx->slot, SLOT_STATUS));
> + if (slot_status & SLOT_STATUS_ONGOING)
> + return true;
> +
> + /*
> + * The curr_desc register is updated when next_descpt_ptr is loaded,
> + * the ongoing bit of slot_status is set when the 32 bytes descriptor is loaded.
> + * So there will be a short time interval in between, which may cause fake false.
> + * Consider read register is quite slow compared with IP read 32byte from memory,
> + * read twice slot_status can avoid this situation.
> + */
> + slot_status = readl(jpeg->base_reg + MXC_SLOT_OFFSET(ctx->slot, SLOT_STATUS));
> + 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 +1007,8 @@ 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
>