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

[Tomasz Figa <tfiga@chromium.org>]

On Tue, Sep 3, 2019 at 8:46 PM Jerry-ch Chen <Jerry-ch.Chen@mediatek.com> wrote:
>
> 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 <Jerry-ch.Chen@mediatek.com> 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 <Jerry-ch.Chen@mediatek.com> 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
> > > > > > <Jerry-ch.Chen@mediatek.com> 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
> > > > > > > > <Jerry-ch.Chen@mediatek.com> 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,

I'm not sure we should be using the functon above as the .job_abort
callback. It's expected to abort the job, but we're just waiting for
it to finish. I think we should just call mtk_fd_job_abort() manually
from .stop_streaming.

> };
>
> 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);

The wake up should be done at the very end of this function. Otherwise
we end up with m2m framework racing with the mtk_fd_hw_job_finish()
below.

Also, I'd use a completion here rather than an open coded wait and
wake-up. The driver could reinit_completion() before queuing a job to
the hardware and the IRQ handler would complete(). There would be no
need to store the IRQ flags in driver data anymore.

>         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);

Please ignore that checkpatch warning, it sometimes gives false
positives. The above looks clearly worse and less consistent with
kernel coding style than what I suggested.

Best regards,
Tomasz

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