Re: [PATCH v2 2/3] media: imx-jpeg: Change the pattern size to 128x64

Ming Qian(OSS)
2025-04-07T02:54:43Z

Hi Sebastian,

On 2025/4/5 23:26, Sebastian Fricke wrote:
> Hey Ming,
>
> On 28.03.2025 14:30, 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.
>>
>> To avoid performance loss, use the smallest supported resolution 64x64
>> as the pattern jpeg size.
>>
>> But there is a hardware issue: when the JPEG decoded frame with a
>> resolution that is no larger than 64x64 and it is followed by a next
>> decoded frame with a larger resolution but not 64 aligned, then this
>> next decoded frame may be corrupted.
>>
>> To avoid corruption of the decoded image, we change the pattern jpeg
>> size to 128x64, as we confirmed with the hardware designer that this is
>> a safe size.
>>
>> Besides, we also need to allocate a dma buffer to store the decoded
>> picture for the pattern image.
>
> Why is that related to the change of the pattern size? Like why wasn't
> that needed for 64x64? And if this solves a different issue, can you put
> that into an extra patch?
>
> This is a bit hard to understand, maybe this is better:
>
> In order to decode a motion-jpeg bitstream, which doesn't provide a DHT,
> the driver will first decode a pattern jpeg and use the DHT found in the
> pattern to decode the first actual frame. This mode is called
> "repeat-mode" and it utilizes linked descriptors.
> The smallest supported resolution of 64x64 was used for that pattern to
> not cause unneeded performance delay. This choice, however, can cause a
> corrupted decoded picture of the first frame after the pattern, when the
> resolution of that frame is larger than the pattern and is not aligned
> to 64.
> By altering the pattern size to 128x64, this corruption can be avoided.
> That size has been confirmed to be safe by the hardware designers.
> Additionally, a DMA buffer needs to be allocated to store the decoded
> picture of the pattern image.
>
> The rest looks good.
>
> Regards,
> Sebastian
>

You're right, and your description is clearer, I'll apply it.
Thanks very much.

Regards,
Ming

>>
>> Signed-off-by: Ming Qian <ming.qian@oss.nxp.com>
>> ---
>> .../media/platform/nxp/imx-jpeg/mxc-jpeg.c | 42 +++++++++++++++----
>> .../media/platform/nxp/imx-jpeg/mxc-jpeg.h | 5 +++
>> 2 files changed, 39 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
>> b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
>> index 12661c177f5a..45705c606769 100644
>> --- a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
>> +++ b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
>> @@ -535,7 +535,18 @@ static const unsigned char jpeg_sos_maximal[] = {
>> };
>>
>> static const unsigned char jpeg_image_red[] = {
>> - 0xFC, 0x5F, 0xA2, 0xBF, 0xCA, 0x73, 0xFE, 0xFE,
>> + 0xF9, 0xFE, 0x8A, 0xFC, 0x34, 0xFD, 0xC4, 0x28,
>> + 0xA0, 0x02, 0x8A, 0x00, 0x28, 0xA0, 0x02, 0x8A,
>> + 0x00, 0x28, 0xA0, 0x02, 0x8A, 0x00, 0x28, 0xA0,
>> + 0x02, 0x8A, 0x00, 0x28, 0xA0, 0x02, 0x8A, 0x00,
>> + 0x28, 0xA0, 0x02, 0x8A, 0x00, 0x28, 0xA0, 0x02,
>> + 0x8A, 0x00, 0x28, 0xA0, 0x02, 0x8A, 0x00, 0x28,
>> + 0xA0, 0x02, 0x8A, 0x00, 0x28, 0xA0, 0x02, 0x8A,
>> + 0x00, 0x28, 0xA0, 0x02, 0x8A, 0x00, 0x28, 0xA0,
>> + 0x02, 0x8A, 0x00, 0x28, 0xA0, 0x02, 0x8A, 0x00,
>> + 0x28, 0xA0, 0x02, 0x8A, 0x00, 0x28, 0xA0, 0x02,
>> + 0x8A, 0x00, 0x28, 0xA0, 0x0F, 0xFF, 0xD0, 0xF9,
>> + 0xFE, 0x8A, 0xFC, 0x34, 0xFD, 0xC4, 0x28, 0xA0,
>> 0x02, 0x8A, 0x00, 0x28, 0xA0, 0x02, 0x8A, 0x00,
>> 0x28, 0xA0, 0x02, 0x8A, 0x00, 0x28, 0xA0, 0x02,
>> 0x8A, 0x00, 0x28, 0xA0, 0x02, 0x8A, 0x00, 0x28,
>> @@ -545,7 +556,7 @@ static const unsigned char jpeg_image_red[] = {
>> 0x28, 0xA0, 0x02, 0x8A, 0x00, 0x28, 0xA0, 0x02,
>> 0x8A, 0x00, 0x28, 0xA0, 0x02, 0x8A, 0x00, 0x28,
>> 0xA0, 0x02, 0x8A, 0x00, 0x28, 0xA0, 0x02, 0x8A,
>> - 0x00, 0x28, 0xA0, 0x02, 0x8A, 0x00
>> + 0x00, 0x28, 0xA0, 0x0F
>> };
>>
>> static const unsigned char jpeg_eoi[] = {
>> @@ -775,6 +786,13 @@ static void mxc_jpeg_free_slot_data(struct
>> mxc_jpeg_dev *jpeg)
>> jpeg->slot_data.cfg_stream_vaddr = NULL;
>> jpeg->slot_data.cfg_stream_handle = 0;
>>
>> + dma_free_coherent(jpeg->dev, jpeg->slot_data.cfg_dec_size,
>> + jpeg->slot_data.cfg_dec_vaddr,
>> + jpeg->slot_data.cfg_dec_daddr);
>> + jpeg->slot_data.cfg_dec_size = 0;
>> + jpeg->slot_data.cfg_dec_vaddr = NULL;
>> + jpeg->slot_data.cfg_dec_daddr = 0;
>> +
>> jpeg->slot_data.used = false;
>> }
>>
>> @@ -814,6 +832,14 @@ static bool mxc_jpeg_alloc_slot_data(struct
>> mxc_jpeg_dev *jpeg)
>> goto err;
>> jpeg->slot_data.cfg_stream_vaddr = cfg_stm;
>>
>> + jpeg->slot_data.cfg_dec_size = MXC_JPEG_PATTERN_WIDTH *
>> MXC_JPEG_PATTERN_HEIGHT * 2;
>> + jpeg->slot_data.cfg_dec_vaddr = dma_alloc_coherent(jpeg->dev,
>> + jpeg->slot_data.cfg_dec_size,
>> + &jpeg->slot_data.cfg_dec_daddr,
>> + GFP_ATOMIC);
>> + if (!jpeg->slot_data.cfg_dec_vaddr)
>> + goto err;
>> +
>> skip_alloc:
>> jpeg->slot_data.used = true;
>>
>> @@ -1216,14 +1242,14 @@ static void mxc_jpeg_config_dec_desc(struct
>> vb2_buffer *out_buf,
>> */
>> *cfg_size = mxc_jpeg_setup_cfg_stream(cfg_stream_vaddr,
>> V4L2_PIX_FMT_YUYV,
>> - MXC_JPEG_MIN_WIDTH,
>> - MXC_JPEG_MIN_HEIGHT);
>> + MXC_JPEG_PATTERN_WIDTH,
>> + MXC_JPEG_PATTERN_HEIGHT);
>> cfg_desc->next_descpt_ptr = desc_handle | MXC_NXT_DESCPT_EN;
>> - cfg_desc->buf_base0 = vb2_dma_contig_plane_dma_addr(dst_buf, 0);
>> + cfg_desc->buf_base0 = jpeg->slot_data.cfg_dec_daddr;
>> cfg_desc->buf_base1 = 0;
>> - cfg_desc->imgsize = MXC_JPEG_MIN_WIDTH << 16;
>> - cfg_desc->imgsize |= MXC_JPEG_MIN_HEIGHT;
>> - cfg_desc->line_pitch = MXC_JPEG_MIN_WIDTH * 2;
>> + cfg_desc->imgsize = MXC_JPEG_PATTERN_WIDTH << 16;
>> + cfg_desc->imgsize |= MXC_JPEG_PATTERN_HEIGHT;
>> + cfg_desc->line_pitch = MXC_JPEG_PATTERN_WIDTH * 2;
>> cfg_desc->stm_ctrl = STM_CTRL_IMAGE_FORMAT(MXC_JPEG_YUV422);
>> cfg_desc->stm_ctrl |= STM_CTRL_BITBUF_PTR_CLR(1);
>> cfg_desc->stm_bufbase = cfg_stream_handle;
>> diff --git a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.h
>> b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.h
>> index 86e324b21aed..fdde45f7e163 100644
>> --- a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.h
>> +++ b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.h
>> @@ -28,6 +28,8 @@
>> #define MXC_JPEG_W_ALIGN 3
>> #define MXC_JPEG_MAX_SIZEIMAGE 0xFFFFFC00
>> #define MXC_JPEG_MAX_PLANES 2
>> +#define MXC_JPEG_PATTERN_WIDTH 128
>> +#define MXC_JPEG_PATTERN_HEIGHT 64
>>
>> enum mxc_jpeg_enc_state {
>> MXC_JPEG_ENCODING = 0, /* jpeg encode phase */
>> @@ -117,6 +119,9 @@ struct mxc_jpeg_slot_data {
>> dma_addr_t desc_handle;
>> dma_addr_t cfg_desc_handle; // configuration descriptor dma address
>> dma_addr_t cfg_stream_handle; // configuration bitstream dma address
>> + dma_addr_t cfg_dec_size;
>> + void *cfg_dec_vaddr;
>> + dma_addr_t cfg_dec_daddr;
>> };
>>
>> struct mxc_jpeg_dev {
>> --
>> 2.43.0-rc1
>>
>>