Message-ID: <CAAFQd5A8XAT-7kZgaKktbBk1ogdfY3LRsK0xapHps4VqCQ_BZA@mail.gmail.com>
Date:   Tue, 10 Mar 2020 13:17:31 +0900
From:   Tomasz Figa <tfiga@...omium.org>
To:     Xia Jiang <xia.jiang@...iatek.com>
Cc:     Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rick Chang <Rick.Chang@...iatek.com>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        srv_heupstream <srv_heupstream@...iatek.com>
Subject: Re: [PATCH v4 5/5] media: platform: Add jpeg dec/enc feature

Hi Xia,

On Fri, Dec 6, 2019 at 6:59 PM Xia Jiang <xia.jiang@...iatek.com> wrote:
>
> On Wed, 2019-10-23 at 18:39 +0800, Tomasz Figa wrote:
> > Hi Xia,
> >
> > On Thu, Oct 17, 2019 at 04:40:38PM +0800, Xia Jiang wrote:
> > > Add mtk jpeg encode v4l2 driver based on jpeg decode, because that jpeg
> > > decode and encode have great similarities with function operation.
> > >
> > > Signed-off-by: Xia Jiang <xia.jiang@...iatek.com>
> > > ---
> > > v4: split mtk_jpeg_try_fmt_mplane() to two functions, one for encoder,
> > >     one for decoder.
> > >     split mtk_jpeg_set_default_params() to two functions, one for
> > >     encoder, one for decoder.
> > >     add cropping support for encoder in g/s_selection ioctls.
> > >     change exif mode support by using V4L2_JPEG_ACTIVE_MARKER_APP1.
> > >     change MTK_JPEG_MAX_WIDTH/MTK_JPEG_MAX_HEIGH from 8192 to 65535 by
> > >     specification.
> > >     move width shifting operation behind aligning operation in
> > >     mtk_jpeg_try_enc_fmt_mplane() for bug fix.
> > >     fix user abuseing data_offset issue for DMABUF in
> > >     mtk_jpeg_set_enc_src().
> > >     fix kbuild warings: change MTK_JPEG_MIN_HEIGHT/MTK_JPEG_MAX_HEIGHT
> > >                         and MTK_JPEG_MIN_WIDTH/MTK_JPEG_MAX_WIDTH from
> > >                         'int' type to 'unsigned int' type.
> > >                         fix msleadingly indented of 'else'.
> > >
> > > v3: delete Change-Id.
> > >     only test once handler->error after the last v4l2_ctrl_new_std().
> > >     seperate changes of v4l2-ctrls.c and v4l2-controls.h to new patch.
> > >
> > > v2: fix compliance test fail, check created buffer size in driver.
> > > ---
> > >  drivers/media/platform/mtk-jpeg/Makefile      |   5 +-
> > >  .../media/platform/mtk-jpeg/mtk_jpeg_core.c   | 731 +++++++++++++++---
> > >  .../media/platform/mtk-jpeg/mtk_jpeg_core.h   | 123 ++-
> > >  .../media/platform/mtk-jpeg/mtk_jpeg_dec_hw.h |   7 +-
> > >  .../media/platform/mtk-jpeg/mtk_jpeg_enc_hw.c | 175 +++++
> > >  .../media/platform/mtk-jpeg/mtk_jpeg_enc_hw.h |  60 ++
> > >  .../platform/mtk-jpeg/mtk_jpeg_enc_reg.h      |  49 ++
> > >  7 files changed, 1004 insertions(+), 146 deletions(-)
> > >  create mode 100644 drivers/media/platform/mtk-jpeg/mtk_jpeg_enc_hw.c
> > >  create mode 100644 drivers/media/platform/mtk-jpeg/mtk_jpeg_enc_hw.h
> > >  create mode 100644 drivers/media/platform/mtk-jpeg/mtk_jpeg_enc_reg.h
> > >
> >
> > First of all, thanks for the patch!
> >
> > Please check my comments below.
> >
> > My general feeling about this code is that the encoder hardware block is
> > completely orthogonal from the decoder block and there is very little code
> > reuse from the original decoder driver.
> >
> > Moreover, a lot of existing code now needs if (decoder) { ... } else {... }
> > segments, which complicates the code.
> >
> > Would it perhaps make sense to instead create a separate mtk-jpeg-enc
> > driver?
> >
> > It would also give us a fresh start in terms of code quality, as the
> > existing mtk-jpeg driver has a lot of quality issues unfortunately. (Some
> > of my comments to this patch actually relate to the issues with the
> > original code, not introduced by this patch, but we need to fix them if
> > changing this driver already.)
> >
> Dear Tomasz,
>
> I haved fixed the driver by following your advice in general.
>
> Please check my reply below.

Sorry, I missed this message originally. Replied below.

[snip]
> > > +   }
> > > +   param->enc_w = q_data_src->w;
> > > +   param->enc_h = q_data_src->h;
> > > +
> > > +   if (jpeg_params->enc_quality >= 97)
> > > +           param->enc_quality = JPEG_ENCODE_QUALITY_Q97;
> > > +   else if (jpeg_params->enc_quality >= 95)
> > > +           param->enc_quality = JPEG_ENCODE_QUALITY_Q95;
> >
> > I'm wondering if the application requests 96, it doesn't expect the quality to
> > be _at_least_ 96.
> our jpeg enc hw do not support quality 96,only support 15 kinds of quant
> table listed here, so if the application requests 96,a nearest and
> highest quality will be given.
> >

Just to clarify my comment, if I remember correctly, the JPEG standard
defines the 100 levels, so if the application requests level 96, but
the hardware provides only 95 and 97, the quality should be favored
and 97 used.

[snip]
> >
> > > +   param->mem_stride = mtk_jpeg_align(width_even, (is_420 ? 16 : 32));
> >
> > What's the difference between img_stride and mem_stride?
>
> In theory, mem_stride need >= img_stride,but we use the same is ok
> >
> > > +   param->total_encdu =
> > > +           ((padding_width >> 4) * (padding_height >> (is_420 ? 4 : 3)) *
> > > +           (is_420 ? 6 : 4)) - 1;
> >
> > The comment above the struct says this is the total number of 8x8 blocks.
> > Why would it depend on whether the format is YUV 4:2:0? Since we should
> > have already aligned the width and height in try_fmt, this should be as
> > simple as (width / 8) * (height / 8).
> becuase the image size is w*h*1.5 for yuv420 format, but w*h*2 for
> yuv422,so for yuv420: w_16/8*h_16/8*1.5-1(because the hw will start at
> number 0), yuv422: w_32/8*h_8/8*2-1,this number is equal to my code.

Do you mean that this also includes the Cb and Cr 8x8 blocks separately?
If so, could it be rewritten as below to improve the readability?

luma_blocks = width / 8 * height / 8;
if (is_420)
    chroma_blocks = luma_blocks / 4;
else
    chroma_blocks = luma_blocks / 2;
param->last_encdu = luma_blocks + 2 * chroma_blocks - 1;

Also, does it mean that this number is actually the index of the last
block, not the total number of blocks?
If so, the field should be probably renamed to last_encdu and the
description updated accordingly.

[snip]
> > Could we instead check the buffer address alignment in .buf_prepare and fail if
> > it's not big enough?
> >
> > > +   bs->dma_addr_offset = p->enable_exif ? MTK_JPEG_DEFAULT_EXIF_SIZE : 0;
> > > +   bs->dma_addr_offsetmask = bs->dma_addr & JPEG_ENC_DST_ADDR_OFFSET_MASK;
> >
> > What is the meaning of this offset mask?
> our actual destination address = destination address + offset address+
> destination address offset mask.The mask 0:No offset,1~15:offset byte
> from the 16-byte aligned

So we have dma_addr, dma_addr_offset and dma_addr_offsetmask. Why do
we need dma_addr_offset? Would the same operation be achieved with the
code below?

dma_addr = vb2_dma_contig_plane_dma_addr(dst_buf, 0);
if (p->enable_exif)
    dma_addr += MTK_JPEG_DEFAULT_EXIF_SIZE;
bs->dma_addr = dma_addr & ~JPEG_ENC_DST_ADDR_OFFSET_MASK;
bs->dma_addr_offset = 0;
bs->dma_addr_offsetmask = dma_addr & JPEG_ENC_DST_ADDR_OFFSET_MASK;

Or does the hardware write something directly at bs->dma_addr (some
tags?) and then the encoded image at the final desintation address?

[snip]
> > > -static void mtk_jpeg_set_default_params(struct mtk_jpeg_ctx *ctx)
> > > +static void mtk_jpeg_set_enc_default_params(struct mtk_jpeg_ctx *ctx)
> > > +{
> > > +   struct mtk_jpeg_q_data *q = &ctx->out_q;
> > > +   int align_w, align_h;
> > > +
> > > +   ctx->fh.ctrl_handler = &ctx->ctrl_hdl;
> > > +
> > > +   ctx->colorspace = V4L2_COLORSPACE_JPEG,
> > > +   ctx->ycbcr_enc = V4L2_YCBCR_ENC_DEFAULT;
> > > +   ctx->quantization = V4L2_QUANTIZATION_DEFAULT;
> > > +   ctx->xfer_func = V4L2_XFER_FUNC_DEFAULT;
> > > +
> > > +   q->w = MTK_JPEG_MIN_WIDTH;
> > > +   q->h = MTK_JPEG_MIN_HEIGHT;
> > > +
> > > +   q->fmt = mtk_jpeg_find_format(ctx, V4L2_PIX_FMT_YUYV,
> > > +                                 MTK_JPEG_FMT_TYPE_OUTPUT);
> > > +
> > > +   align_w = q->w;
> > > +   align_h = q->h;
> > > +   align_w = round_up(align_w, 2);
> > > +   v4l_bound_align_image(&align_w, MTK_JPEG_MIN_WIDTH, MTK_JPEG_MAX_WIDTH,
> > > +                         5, &align_h, MTK_JPEG_MIN_HEIGHT,
> > > +                         MTK_JPEG_MAX_HEIGHT, 3, 0);
> > > +   align_w = align_w << 1;
> > > +
> > > +   if (align_w < MTK_JPEG_MIN_WIDTH &&
> > > +       (align_w + 32) <= MTK_JPEG_MAX_WIDTH)
> > > +           align_w += 32;
> > > +   if (align_h < MTK_JPEG_MIN_HEIGHT &&
> > > +       (align_h + 8) <= MTK_JPEG_MAX_HEIGHT)
> > > +           align_h += 8;
> > > +
> > > +   q->sizeimage[0] = align_w * align_h;
> > > +   q->bytesperline[0] = align_w;
> > > +
> > > +   q = &ctx->cap_q;
> > > +   q->w = MTK_JPEG_MIN_WIDTH;
> > > +   q->h = MTK_JPEG_MIN_HEIGHT;
> > > +   q->fmt = mtk_jpeg_find_format(ctx, V4L2_PIX_FMT_JPEG,
> > > +                                 MTK_JPEG_FMT_TYPE_CAPTURE);
> > > +   q->bytesperline[0] = 0;
> > > +   q->sizeimage[0] = MTK_JPEG_DEFAULT_SIZEIMAGE;
> > > +}
> >
> > Could we just create an arbitrary v4l2_pix_format_mplane struct and call
> > s_fmt instead? In general, all of the constant values and alignments should
> > be already ensured by try_fmt, so this function should be redundant.
> if cancel this function,the v4l2-compliance test will fail

Sorry, I guess my comment was not clear. We need to initialize the
default parameters. However, the contents of this function seem to
heavily duplicate with the code that should be in try_fmt, so could we
just call try_fmt from here instead of repeating the calculations?

[snip]
> > > -   ret = devm_request_irq(&pdev->dev, dec_irq, mtk_jpeg_dec_irq, 0,
> > > +   ret = devm_request_irq(&pdev->dev, jpeg_irq, mtk_jpeg_irq, 0,
> > >                            pdev->name, jpeg);
> > >     if (ret) {
> > > -           dev_err(&pdev->dev, "Failed to request dec_irq %d (%d)\n",
> > > -                   dec_irq, ret);
> > > -           ret = -EINVAL;
> >
> > This removal of ret assignment looks like a separate fix that should be
> > done in its own patch.
> this change is because of the adding of jpeg enc driver,not the orignal
> driver' question, should I move it to the orignal driver's patch?

Yes, please.

> >
> > > +           dev_err(&pdev->dev, "Failed to request jpeg_irq %d (%d)\n",
> > > +                   jpeg_irq, ret);
> > >             goto err_req_irq;
> > >     }
> > >
> > > @@ -1140,33 +1602,35 @@ static int mtk_jpeg_probe(struct platform_device *pdev)
> > >             goto err_m2m_init;
> > >     }
> > >
> > > -   jpeg->dec_vdev = video_device_alloc();
> > > -   if (!jpeg->dec_vdev) {
> > > +   jpeg->vfd_jpeg = video_device_alloc();
> > > +   if (!jpeg->vfd_jpeg) {
> > >             ret = -ENOMEM;
> > > -           goto err_dec_vdev_alloc;
> > > +           goto err_vfd_jpeg_alloc;
> > >     }
> > > -   snprintf(jpeg->dec_vdev->name, sizeof(jpeg->dec_vdev->name),
> > > -            "%s-dec", MTK_JPEG_NAME);
> > > -   jpeg->dec_vdev->fops = &mtk_jpeg_fops;
> > > -   jpeg->dec_vdev->ioctl_ops = &mtk_jpeg_ioctl_ops;
> > > -   jpeg->dec_vdev->minor = -1;
> > > -   jpeg->dec_vdev->release = video_device_release;
> > > -   jpeg->dec_vdev->lock = &jpeg->lock;
> > > -   jpeg->dec_vdev->v4l2_dev = &jpeg->v4l2_dev;
> > > -   jpeg->dec_vdev->vfl_dir = VFL_DIR_M2M;
> > > -   jpeg->dec_vdev->device_caps = V4L2_CAP_STREAMING |
> > > +   snprintf(jpeg->vfd_jpeg->name, sizeof(jpeg->vfd_jpeg->name),
> > > +            "%s-%s", MTK_JPEG_NAME,
> > > +            jpeg->mode == MTK_JPEG_ENC ? "enc" : "dec");
> > > +   jpeg->vfd_jpeg->fops = &mtk_jpeg_fops;
> > > +   jpeg->vfd_jpeg->ioctl_ops = &mtk_jpeg_ioctl_ops;
> > > +   jpeg->vfd_jpeg->minor = -1;
> > > +   jpeg->vfd_jpeg->release = video_device_release;
> > > +   jpeg->vfd_jpeg->lock = &jpeg->lock;
> > > +   jpeg->vfd_jpeg->v4l2_dev = &jpeg->v4l2_dev;
> > > +   jpeg->vfd_jpeg->vfl_dir = VFL_DIR_M2M;
> > > +   jpeg->vfd_jpeg->device_caps = V4L2_CAP_STREAMING |
> > >                                   V4L2_CAP_VIDEO_M2M_MPLANE;
> > >
> > > -   ret = video_register_device(jpeg->dec_vdev, VFL_TYPE_GRABBER, 3);
> > > +   ret = video_register_device(jpeg->vfd_jpeg, VFL_TYPE_GRABBER, -1);
> >
> > The change from 3 to -1 also looks like something for a separate patch.
> same as the above reply

Ditto.

[snip]
> > > @@ -17,23 +18,77 @@
> > >
> > >  #define MTK_JPEG_FMT_FLAG_DEC_OUTPUT       BIT(0)
> > >  #define MTK_JPEG_FMT_FLAG_DEC_CAPTURE      BIT(1)
> > > +#define MTK_JPEG_FMT_FLAG_ENC_OUTPUT       BIT(2)
> > > +#define MTK_JPEG_FMT_FLAG_ENC_CAPTURE      BIT(3)
> > >
> > >  #define MTK_JPEG_FMT_TYPE_OUTPUT   1
> > >  #define MTK_JPEG_FMT_TYPE_CAPTURE  2
> > >
> > > -#define MTK_JPEG_MIN_WIDTH 32
> > > -#define MTK_JPEG_MIN_HEIGHT        32
> > > -#define MTK_JPEG_MAX_WIDTH 8192
> > > -#define MTK_JPEG_MAX_HEIGHT        8192
> > > +#define MTK_JPEG_MIN_WIDTH 32U
> > > +#define MTK_JPEG_MIN_HEIGHT        32U
> > > +#define MTK_JPEG_MAX_WIDTH 65535U
> > > +#define MTK_JPEG_MAX_HEIGHT        65535U
> >
> > Why is it okay to change this from 8192 to 65535?
> our hw support max width/height to 65535

Does this also apply to the JPEG decoder on MT8173 for which the
driver was developed?

[snip]
> > > +/**
> > > + * jpeg_enc_param - parameters of jpeg encode control
> > > + * @enable_exif:   EXIF enable for jpeg encode mode
> > > + * @enc_quality:   destination image quality in encode mode
> > > + * @restart_interval:      JPEG restart interval for JPEG encoding
> > > + */
> > > +struct jpeg_enc_param {
> > > +   u32 enable_exif;
> >
> > Shouldn't this be a bool?
> this value is seted by V4L2_CID_JPEG_ACTIVE_MARKER control,its' value is
> V4L2_JPEG_ACTIVE_MARKER_APP1(1<<1),not a bool

In this case, please call it active_marker and also update the comment
above accordingly.

Still, if this driver only cares about V4L2_JPEG_ACTIVE_MARKER_APP1,
bool enable_exif, assigned  by the code appropriately, would make more
sense.

[snip]
> > > +
> > > +static void mtk_jpeg_enc_set_encFormat(void __iomem *base, u32 enc_format)
> > > +{
> > > +   u32 value;
> > > +
> > > +   value = readl(base + JPGENC_CTRL);
> > > +   value &= ~JPEG_ENC_CTRL_YUV_BIT;
> > > +   value |= JPGENC_FORMAT(enc_format);
> > > +   writel(value, base + JPGENC_CTRL);
> >
> > The model I suggested above also avoids this kind of read modify write
> > operations, which just unnecessarily add synchronous MMIO round trips, which
> > means more CPU overhead.
> >
> > Given that the full state is always known by the driver, it can just write
> > all the register values without the need to read them back.
> the JPGENC_CTRL register has 32 bits,different bits have different
> meanings. encformat is bit 3~4,so we need ready before write to
> guarantee other bits' value not be changed

I explained this more in my review comments to the latest revision,
but this is just solving a problem that is introduced by the design of
the code. If the code was designed so that 1 register is only changed
in 1 function, there would be no need to read back the registers,
because the function would initialize the full register at a time.
That's what most of the other drivers do.

[snip]
> > > +enum {
> > > +   MTK_JPEG_ENC_RESULT_DONE                = 0,
> > > +   MTK_JPEG_ENC_RESULT_STALL,
> > > +   MTK_JPEG_ENC_RESULT_VCODEC_IRQ,
> > > +   MTK_JPEG_ENC_RESULT_ERROR_UNKNOWN
> > > +};
> >
> > Do we need these intermediate error codes? Could we just use errno values
> > instead?
> we can just use errno values,but our interrupt status have three
> state,done/stall,vcodec irq,maybe listing them here makes more clarity

I suggested another approach in my comments for the latest revision.
Generally the interrupt handler is the only place where this error
handling is done, so the intermediate error codes shouldn't be
necessary, as the interrupt handler would directly signal any issues
to V4L2.

[snip]
> > > +#define JPGENC_FORMAT(x)           (((x) & 3) << 3)
> > > +#define JPGENC_WIDTH_HEIGHT(w, h)  (((w) << 16) | (h))
> > > +#define JPGENC_INIT_OFFSET(x)              ((x) & (~0xF))
> > > +#define JPGENC_OFFSET_MASK(x)              ((x) & 0xF)
> > > +#define JPGENC_DST_ADDR(x)         ((x) & (~0xF))
> > > +#define JPGENC_STALL_ADDR(x, y)            (((x) + (y)) & (~0xF))
> > > +#define JPGENC_QUALITY_MASK                0xFFFF0000
> > > +#define JPGENC_SET_QUALITY(x, y)   (((x) & JPGENC_QUALITY_MASK) | (y))
> >
> > JPGENC_QUALITY_MASK is only used here, so 0xffff0000 could be just used
> > directly.
> done
> >
> > > +
> > > +#endif /* _MTK_JPEG_ENC_REG_H */
> >
> > I can see some bits defined in mtk_jpeg_enc_hw.h as well. Perhaps all these
> > could be moved there too, which would make us have 1 file less?
> moved bits defined  and register defined to mtk_jpeg_enc_reg.h, but the
> functions declaration about jpeg enc hw were in mtk_jpeg_enc_hw.h, is
> that ok?

My suggestion was the other way around - have all the encoder-specific
definitions in mtk_jpeg_enc_hw.h and remove mtk_jpeg_enc_reg.h.

In general, this is a relatively simple hardware block and we should
be able to just have one file that deals with hardware registers. Then
there would be no need for headers, as the register definitions could
be put directly in the source file. A rule of thumb is to use a header
when something needs to be shared between multiple source files.

Best regards,
Tomasz

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