Date:   Wed, 1 Jul 2020 13:07:48 +0200
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 Mailing List <linux-media@...r.kernel.org>,
        linux-devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        srv_heupstream <srv_heupstream@...iatek.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        mojahsu@...omium.org, Nicolas Boichat <drinkcat@...omium.org>,
        Maoguang Meng (孟毛广) 
        <maoguang.meng@...iatek.com>, Sj Huang <sj.huang@...iatek.com>
Subject: Re: [PATCH RESEND v9 18/18] media: platform: Add jpeg enc feature

On Wed, Jul 1, 2020 at 10:29 AM Xia Jiang <xia.jiang@...iatek.com> wrote:
>
> On Tue, 2020-06-30 at 16:53 +0000, Tomasz Figa wrote:
> > Hi Xia,
> >
> > On Tue, Jun 30, 2020 at 10:56:21AM +0800, Xia Jiang wrote:
> > > On Thu, 2020-06-11 at 18:46 +0000, Tomasz Figa wrote:
> > > > Hi Xia,
> > > >
> > > > On Thu, Jun 04, 2020 at 05:05:53PM +0800, Xia Jiang wrote:
> > [snip]
> > > > > +static void mtk_jpeg_enc_device_run(void *priv)
> > > > > +{
> > > > > +       struct mtk_jpeg_ctx *ctx = priv;
> > > > > +       struct mtk_jpeg_dev *jpeg = ctx->jpeg;
> > > > > +       struct vb2_v4l2_buffer *src_buf, *dst_buf;
> > > > > +       enum vb2_buffer_state buf_state = VB2_BUF_STATE_ERROR;
> > > > > +       unsigned long flags;
> > > > > +       struct mtk_jpeg_src_buf *jpeg_src_buf;
> > > > > +       struct mtk_jpeg_enc_bs enc_bs;
> > > > > +       int ret;
> > > > > +
> > > > > +       src_buf = v4l2_m2m_next_src_buf(ctx->fh.m2m_ctx);
> > > > > +       dst_buf = v4l2_m2m_next_dst_buf(ctx->fh.m2m_ctx);
> > > > > +       jpeg_src_buf = mtk_jpeg_vb2_to_srcbuf(&src_buf->vb2_buf);
> > > > > +
> > > > > +       ret = pm_runtime_get_sync(jpeg->dev);
> > > > > +       if (ret < 0)
> > > > > +               goto enc_end;
> > > > > +
> > > > > +       spin_lock_irqsave(&jpeg->hw_lock, flags);
> > > > > +
> > > > > +       /*
> > > > > +        * Resetting the hardware every frame is to ensure that all the
> > > > > +        * registers are cleared. This is a hardware requirement.
> > > > > +        */
> > > > > +       mtk_jpeg_enc_reset(jpeg->reg_base);
> > > > > +
> > > > > +       mtk_jpeg_set_enc_dst(ctx, jpeg->reg_base, &dst_buf->vb2_buf, &enc_bs);
> > > > > +       mtk_jpeg_set_enc_src(ctx, jpeg->reg_base, &src_buf->vb2_buf);
> > > > > +       mtk_jpeg_enc_set_config(jpeg->reg_base, ctx->out_q.fmt->hw_format,
> > > > > +                               ctx->enable_exif, ctx->enc_quality,
> > > > > +                               ctx->restart_interval);
> > > > > +       mtk_jpeg_enc_start(jpeg->reg_base);
> > > >
> > > > Could we just move the above 5 functions into one function inside
> > > > mtk_jpeg_enc_hw.c that takes mtk_jpeg_dev pointer as its argument, let's
> > > > say mtk_jpeg_enc_hw_run() and simply program all the data to the registers
> > > > directly, without the extra level of abstractions?
> > > I can move the 5 functions into one function(mtk_jpeg_enc_hw_run()), but
> > > this function will be very long, because it contains computation code
> > > such as setting dst addr, blk_num, quality.
> > > In v4, you have adviced the following architecture:
> > > How about the following model, as used by many other drivers:
> > >
> > > mtk_jpeg_enc_set_src()
> > > {
> > >         // Set any registers related to source format and buffer
> > > }
> > >
> > > mtk_jpeg_enc_set_dst()
> > > {
> > >         // Set any registers related to destination format and buffer
> > > }
> > >
> > > mtk_jpeg_enc_set_params()
> > > {
> > >         // Set any registers related to additional encoding parameters
> > > }
> > >
> > > mtk_jpeg_enc_device_run(enc, ctx)
> > > {
> > >         mtk_jpeg_enc_set_src(enc, src_buf, src_fmt);
> > >         mtk_jpeg_enc_set_dst(enc, dst_buf, dst_fmt);
> > >         mtk_jpeg_enc_set_params(enc, ctx);
> > >         // Trigger the hardware run
> > > }
> > > I think that this architecture is more clear(mtk_jpeg_enc_set_config is
> > > equivalent to mtk_jpeg_enc_set_params).
> > > Should I keep the original architecture or move 5 functions into
> > > mtk_jpeg_enc_hw_run?
> >
> > Sounds good to me.
> >
> > My biggest issue with the code that it ends up introducing one more
> > level of abstraction, but with the approach you suggested, the arguments
> > just accept standard structs, which avoids that problem.
> Dear Tomasz,
>
> Sorry for that I didn't understand your final preference.
>
> As you mentioned, using mtk_jpeg_dev pointer as its argument, but some
> arguments come from mtk_jpeg_ctx pointer, such as ctx->enable_exif/
> ctx->enc_quality/ctx->restart_interval. Should we use  mtk_jpeg_ctx
> pointer as its argument? Should we use src_dma_addr/dst_dma_addr as its
> arguments too? Because that src_dma_addr/dst_dma_addr need to be getted
> by v4l2 interfaces(
> src_buf=v4l2_m2m_next_src_buf();
> src_dma_ddr=vb2_dma_contig_plane_dma_addr();).
> Using V4L2 interfaces in mtk_jpeg_enc_hw.c doesn't seem reasonable.
>
> solution 1:
> mtk_jpeg_enc_hw_run(ctx, src_dma_addr, dst_dma_addr)
> {
>         //Set all the registers
> without one more level of abstraction
> }
>
> solution 2:
> mtk_jpeg_enc_reset(jpeg)
> {
>         //set the reset register
> }
>
> mtk_jpeg_set_enc_dst(ctx, dst_dma_addr)
> {
>
>         //Set any registers related to destination format and buffer
> without one more level of abstraction
> }
> mtk_jpeg_set_enc_src(ctx, src_dma_addr)
> {
>
>         //Set any registers related to source format and buffer     without one
> more level of abstraction
> }
> mtk_jpeg_enc_set_config(ctx)
> {
>         // Set any registers related to additional encoding parameters
> without one more level of abstraction
> }
> mtk_jpeg_enc_start(jpeg)
> {
>         //set the trigger register
> }
>
> Solution 1 or Solution 2?

I like your previous proposal the most. Let me quote it below:

mtk_jpeg_enc_set_src()
{
        // Set any registers related to source format and buffer
}

mtk_jpeg_enc_set_dst()
{
        // Set any registers related to destination format and buffer
}

mtk_jpeg_enc_set_params()
{
        // Set any registers related to additional encoding parameters
}

mtk_jpeg_enc_device_run(enc, ctx)
{
        mtk_jpeg_enc_set_src(enc, src_buf, src_fmt);
        mtk_jpeg_enc_set_dst(enc, dst_buf, dst_fmt);
        mtk_jpeg_enc_set_params(enc, ctx);
        // Trigger the hardware run
}

That is assuming src/dst_buf would be vb2_buffer and src/dst_fmt
v4l2_pix_format_mplane. Does it make sense?

Best regards,
Tomasz

>
> Best Regards,
> Xia Jiang
> >
> > [snip]
> > > > > +
> > > > > +       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;
> > > >
> > > > Since we already have a v4l2_pix_format_mplane struct which has fields for
> > > > the above 4 values, could we just store them there?
> > > >
> > > > Also, I don't see this driver handling the colorspaces in any way, but it
> > > > seems to allow changing them from the userspace. This is incorrect, because
> > > > the userspace has no way to know that the colorspace is not handled.
> > > > Instead, the try_fmt implementation should always override the
> > > > userspace-provided colorspace configuration with the ones that the driver
> > > > assumes.
> > > >
> > > > > +       pix_mp->width = MTK_JPEG_MIN_WIDTH;
> > > > > +       pix_mp->height = MTK_JPEG_MIN_HEIGHT;
> > > > > +
> > > > > +       q->fmt = mtk_jpeg_find_format(V4L2_PIX_FMT_YUYV,
> > > > > +                                     MTK_JPEG_FMT_FLAG_ENC_OUTPUT);
> > > > > +       vidioc_try_fmt(container_of(pix_mp, struct v4l2_format,
> > > > > +                                   fmt.pix_mp), q->fmt);
> > > > > +       q->w = pix_mp->width;
> > > > > +       q->h = pix_mp->height;
> > > > > +       q->crop_rect.width = pix_mp->width;
> > > > > +       q->crop_rect.height = pix_mp->height;
> > > > > +       q->sizeimage[0] = pix_mp->plane_fmt[0].sizeimage;
> > > > > +       q->bytesperline[0] = pix_mp->plane_fmt[0].bytesperline;
> > > >
> > > > Actually, do we need this custom mtk_jpeg_q_data struct? Why couldn't we
> > > > just keep the same values inside the standard v4l2_pix_format_mplane
> > > > struct?
> > > I think that we need mtk_jpeg_q_data struct.If we delete it, how can we
> > > know these values(w, h, sizeimage, bytesperline, mtk_jpeg_fmt) belong to
> > > output or capture(output and capture's sizeimages are different, width
> > > and height are differnt too for jpeg dec )?We have
> > > s_fmt_vid_out_mplane/cap_mplane function to set these values.
> > >
> > > But we can use standard v4l2_pix_format_mplane struct replacing the w, h
> > > bytesperline, sizeimage in mtk_jpeg_q_data struct like this:
> > > struct mtk_jpeg_q_data{
> > >     struct mtk_jpeg_fmt *fmt;
> > >     struct v4l2_pix_format_mplane pix_mp;
> > >     struct v4l2_rect enc_crop_rect
> > > }
> > > Then delete ctx->colorspace ctx->ycbcr_enc ctx->quantization
> > > ctx->xfer_func, becuase v4l2_pix_format_mplane in q_data has contained
> > > them and assign them for out_q and cap_q separately.
> > >
> > > WDYT?
> >
> > Sounds good to me. I was considering just making it like
> >
> > struct mtk_jpeg_ctx {
> >       struct mtk_jpeg_fmt *src_fmt;
> >       struct v4l2_pix_format_mplane src_pix_mp;
> >       struct v4l2_rect src_crop;
> >
> >       struct mtk_jpeg_fmt *dst_fmt;
> >       struct v4l2_pix_format_mplane dst_pix_mp;
> >       struct v4l2_rect dst_crop;
> > };
> >
> > but I like your suggestion as well, as long as custom data structures
> > are not used to store standard information.
> > [snip]
> > > > > @@ -1042,8 +1619,12 @@ static int mtk_jpeg_probe(struct platform_device *pdev)
> > > > >                 return jpeg_irq;
> > > > >         }
> > > > >
> > > > > -       ret = devm_request_irq(&pdev->dev, jpeg_irq, mtk_jpeg_dec_irq, 0,
> > > > > -                              pdev->name, jpeg);
> > > > > +       if (jpeg->variant->is_encoder)
> > > > > +               ret = devm_request_irq(&pdev->dev, jpeg_irq, mtk_jpeg_enc_irq,
> > > > > +                                      0, pdev->name, jpeg);
> > > > > +       else
> > > > > +               ret = devm_request_irq(&pdev->dev, jpeg_irq, mtk_jpeg_dec_irq,
> > > > > +                                      0, pdev->name, jpeg);
> > > >
> > > > Rather than having "is_encoder" in the variant struct, would it make more
> > > > sense to have "irq_handler" instead? That would avoid the explicit if.
> > > Do you mean to delete "is_encoder"? It is used 8 times in the
> > > driver.Should I move them all to the match data?
> >
> > Yes. It would make the code linear and the varability between the
> > decoder and encoder would be self-contained in the variant struct.
> >
> > Best regards,
> > Tomasz
>

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