Subject: Re: [RFC PATCH V2 4/4] platform: mtk-isp: Add Mediatek FD driver

From: Jerry-ch Chen <[email-masked]>
Date: Tue, 3 Sep 2019 14:44:41 +0800

On Tue, 2019-09-03 at 13:19 +0800, Tomasz Figa wrote:
> On Mon, Sep 2, 2019 at 8:47 PM Jerry-ch Chen <[email-masked]> wrote:
> >
> > Hi Tomasz,
> >
> > On Fri, 2019-08-30 at 16:33 +0800, Tomasz Figa wrote:
> > > On Wed, Aug 28, 2019 at 11:00 AM Jerry-ch Chen
> > > <[email-masked]> wrote:
> > > >
> > > > Hi Tomasz,
> > > >
> > > > On Mon, 2019-08-26 at 14:36 +0800, Tomasz Figa wrote:
> > > > > Hi Jerry,
> > > > >
> > > > > On Sun, Aug 25, 2019 at 6:18 PM Jerry-ch Chen
> > > > > <[email-masked]> wrote:
> > > > > >
> > > > > > Hi Tomasz,
> > > > > >
> > > > > > On Fri, 2019-08-02 at 16:28 +0800, Tomasz Figa wrote:
> > > > > > > Hi Jerry,
> > > > > > >
> > > > > > > On Tue, Jul 09, 2019 at 04:41:12PM +0800, Jerry-ch Chen wrote:
> [snip]
> > > > static int mtk_fd_vb2_queue_setup(struct vb2_queue *vq,
> > > >                                   unsigned int *num_buffers,
> > > >                                   unsigned int *num_planes,
> > > >                                   unsigned int sizes[],
> > > >                                   struct device *alloc_devs[])
> > > > {
> > > >         struct mtk_fd_ctx *ctx = vb2_get_drv_priv(vq);
> > > >         struct device *dev = ctx->dev;
> > > >         unsigned int size[2];
> > > >
> > > >         switch (vq->type) {
> > > >         case V4L2_BUF_TYPE_META_CAPTURE:
> > > >                 size[0] = ctx->dst_fmt.buffersize;
> > > >                 break;
> > > >         case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
> > > >                 size[0] = ctx->src_fmt.plane_fmt[0].sizeimage;
> > > >                 if (*num_planes == 2)
> > > >                         size[1] = ctx->src_fmt.plane_fmt[1].sizeimage;
> > > >                 break;
> > > >         }
> > > >
> > > >         if (*num_planes == 1) {
> > > >                 if (sizes[0] < size[0])
> > > >                         return -EINVAL;
> > > >         } else if (*num_planes == 2) {
> > > >                 if ((sizes[0] < size[0]) && (sizes[1] < size[1]))
> > > >                         return -EINVAL;
> > >
> > > Can we just use a loop here and combine the 2 cases above?
> > >
> > > Also, we need to fail with -EINVAL if *num_planes is > 2.
> > >
> > > >         } else {
> > > >                 *num_planes = 1;
> > > >                 sizes[0] = size[0];
> > >
> > > This should be the case if *num_planes == 0 and the number of planes
> > > and sizes should match the currently active format.
> > >
> > I appreciate your comments,
> >
> > Ok, I will update as following:
> > static int mtk_fd_vb2_queue_setup(struct vb2_queue *vq,
> >                                   unsigned int *num_buffers,
> >                                   unsigned int *num_planes,
> >                                   unsigned int sizes[],
> >                                   struct device *alloc_devs[])
> > {
> >         struct mtk_fd_ctx *ctx = vb2_get_drv_priv(vq);
> >         unsigned int size[2];
> >         unsigned int plane;
> >
> >         switch (vq->type) {
> >         case V4L2_BUF_TYPE_META_CAPTURE:
> >                 size[0] = ctx->dst_fmt.buffersize;
> >                 break;
> >         case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
> >                 size[0] = ctx->src_fmt.plane_fmt[0].sizeimage;
> >                 if (*num_planes == 2)
> >                         size[1] = ctx->src_fmt.plane_fmt[1].sizeimage;
> >                 break;
> >         }
> >
> >         if (*num_planes > 2)
> >                 return -EINVAL;
> >         if (*num_planes == 0) {
> >                 if (vq->type == V4L2_BUF_TYPE_META_CAPTURE) {
> >                         sizes[0] = ctx->dst_fmt.buffersize;
> >                         *num_planes = 1;
> >                         return 0;
> >                 }
> >
> >                 *num_planes = ctx->src_fmt.num_planes;
> >                 for (plane = 0; plane < *num_planes; plane++)
> >                         sizes[plane] = ctx->src_fmt.plane_fmt[plane].sizeimage;
> >                 return 0;
> >         }
> >
> >         for (plane = 0; plane < *num_planes; plane++) {
> >                 if(sizes[plane] < size[plane])
> >                         return -EINVAL;
> >         }
> >         return 0;
> > }
> >
> 
> Looks good, thanks!
> 
> > > >         }
> > > >
> > > >         return 0;
> > > > }
> > > >
> > > > > [snip]
> > > > >
> > > > > > > > +static void mtk_fd_vb2_stop_streaming(struct vb2_queue *vq)
> > > > > > > > +{
> > > > > > > > +   struct mtk_fd_ctx *ctx = vb2_get_drv_priv(vq);
> > > > > > > > +   struct vb2_buffer *vb;
> > > > > > >
> > > > > > > How do we guarantee here that the hardware isn't still accessing the buffers
> > > > > > > removed below?
> > > > > > >
> > > > > > Maybe we can check the driver state flag and aborting the unfinished
> > > > > > jobs?
> > > > > > (fd_hw->state == FD_ENQ)
> > > > > >
> > > > >
> > > > > Yes, we need to either cancel or wait for the currently processing
> > > > > job. It depends on hardware capabilities, but cancelling is generally
> > > > > preferred for the lower latency.
> > > > >
> > > > Ok, it the state is ENQ, then we can disable the FD hw by controlling
> > > > the registers.
> > > >
> > > > for example:
> > > >         writel(0x0, fd->fd_base + FD_HW_ENABLE);
> > > >         writel(0x0, fd->fd_base + FD_INT_EN);
> > > >
> > >
> > > What's exactly the effect of writing 0 to FD_HW_ENABLE?
> > >
> > Sorry, my last reply didn't solve the question,
> > we should implement a mtk_fd_job_abort() for v4l2_m2m_ops().
> >
> > which is able to readl_poll_timeout_atomic()
> > and check the HW busy bits in the register FD_INT_EN;
> >
> > if they are not cleared until timeout, we could handle the last
> > processing job.
> > Otherwise, the FD irq handler should have handled the last processing
> > job and we could continue the stop_streaming().
> >
> > For job_abort():
> > static void mtk_fd_job_abort(void *priv)
> > {
> >         struct mtk_fd_ctx *ctx = priv;
> >         struct mtk_fd_dev *fd = ctx->fd_dev;
> >         u32 val;
> >         u32 ret;
> >
> >         ret = readl_poll_timeout_atomic(fd->fd_base + MTK_FD_REG_OFFSET_INT_EN,
> >                                         val,
> >                                         (val & MTK_FD_HW_BUSY_MASK) ==
> >                                         MTK_FD_HW_STATE_IS_BUSY,
> >                                         USEC_PER_MSEC, MTK_FD_STOP_HW_TIMEOUT);
> 
> Hmm, would it be possible to avoid the busy wait by having a
> completion that could be signalled from the interrupt handler?
> 
> Best regards,
> Tomasz

I suppose that would be wakeup a wait queue in the interrupt handler,
the the wait_event_interrupt_timeout() will be used in here and system
suspend e.g. mtk_fd_suspend().
Or do you suggest to wait_event_interrupt_timeout() every frame in the
mtk_fd_ipi_handler()?
I think maybe the readl_poll_timeout_atomic would be good enough.

One more thing, for the mtk_fd_video_device_register()
Sorry that I would need to use intermediate variable here since the 80
columns check.

	function = MEDIA_ENT_F_PROC_VIDEO_STATISTICS;
	ret = v4l2_m2m_register_media_controller(m2m_dev, vfd, function);
	if (ret) {
		dev_err(dev, "Failed to init mem2mem media controller\n");
		goto err_unreg_video;
	}

Thanks and Best regards,
Jerry

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