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 19:46:09 +0800

Hi Tomasz,

On Tue, 2019-09-03 at 15:04 +0800, Tomasz Figa wrote:
> On Tue, Sep 3, 2019 at 3:44 PM Jerry-ch Chen <[email-masked]> wrote:
> >
> > 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().
> 
> Yes, that should work.
> 
> > Or do you suggest to wait_event_interrupt_timeout() every frame in the
> > mtk_fd_ipi_handler()?
> 
> Nope, we shouldn't need that.
> 
> > I think maybe the readl_poll_timeout_atomic would be good enough.
> >
> 
> Not really. Busy waiting should be avoided as much as possible. What's
> the point of entering suspend if you end up burning the power by
> spinning the CPU for some milliseconds?
> 
Ok, I see, busy waiting is not a good idea, I will use the wait queue
instead. the job abort will refine as following:

static void mtk_fd_job_abort(void *priv)
{
	struct mtk_fd_ctx *ctx = priv;
	struct mtk_fd_dev *fd = ctx->fd_dev;
	u32 ret;

	ret = wait_event_interruptible_timeout
		(fd->wq, (fd->fd_irq_result & MTK_FD_HW_IRQ_MASK),
		 usecs_to_jiffies(50000));
	if (ret)
		mtk_fd_hw_job_finish(fd, VB2_BUF_STATE_ERROR);
	dev_dbg(fd->dev, "%s, ret:%d\n", __func__, ret);

	fd->fd_irq_result = 0;
}

static struct v4l2_m2m_ops fd_m2m_ops = {
	.device_run = mtk_fd_device_run,
	.job_abort = mtk_fd_job_abort,
};

and we could use it in suspend.
static int mtk_fd_suspend(struct device *dev)
{
	struct mtk_fd_dev *fd = dev_get_drvdata(dev);

	if (pm_runtime_suspended(dev))
		return 0;

	if (fd->fd_stream_count)
		mtk_fd_job_abort(fd->ctx);

	/* suspend FD HW */
	writel(0x0, fd->fd_base + MTK_FD_REG_OFFSET_INT_EN);
	writel(0x0, fd->fd_base + MTK_FD_REG_OFFSET_HW_ENABLE);
	clk_disable_unprepare(fd->fd_clk);
	dev_dbg(dev, "%s:disable clock\n", __func__);

	return 0;
}

static irqreturn_t mtk_fd_irq(int irq, void *data)
{
	struct mtk_fd_dev *fd = (struct mtk_fd_dev *)data;

	fd->fd_irq_result = readl(fd->fd_base + MTK_FD_REG_OFFSET_INT_VAL);
	wake_up_interruptible(&fd->wq);
	fd->output->number = readl(fd->fd_base + MTK_FD_REG_OFFSET_RESULT);
	dev_dbg(fd->dev, "mtk_fd_face_num:%d\n", fd->output->number);

	pm_runtime_put((fd->dev));
	mtk_fd_hw_job_finish(fd, VB2_BUF_STATE_DONE);
	return IRQ_HANDLED;
}
> >
> > 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);
> 
> Why not just make it like this:
> 
> ret = v4l2_m2m_register_media_controller(m2m_dev,
>                 MEDIA_ENT_F_PROC_VIDEO_STATISTICS);
> 
> The above line is aligned using tabs so that its end is as close to
> the 80 character boundary as possible.
> 
I tried but the checkpatch script still gave me a check saying align to
the scope, I will refine as following:

	ret = v4l2_m2m_register_media_controller
		(m2m_dev, vfd, MEDIA_ENT_F_PROC_VIDEO_STATISTICS);

Thanks and best regards,
Jerry
> Best regards,
> Tomasz

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