Re: [RFC,v3 6/9] media: platform: Add Mediatek ISP P1 V4L2 functions

[Tomasz Figa <tfiga@chromium.org>]

On Mon, Jul 29, 2019 at 10:18 AM Jungo Lin <jungo.lin@mediatek.com> wrote:
> On Fri, 2019-07-26 at 14:49 +0900, Tomasz Figa wrote:
> > On Wed, Jul 24, 2019 at 1:31 PM Jungo Lin <jungo.lin@mediatek.com> wrote:
> > > On Tue, 2019-07-23 at 19:21 +0900, Tomasz Figa wrote:
> > > > On Thu, Jul 18, 2019 at 1:39 PM Jungo Lin <jungo.lin@mediatek.com> wrote:
> > > > > On Wed, 2019-07-10 at 18:54 +0900, Tomasz Figa wrote:
> > > > > > On Tue, Jun 11, 2019 at 11:53:41AM +0800, Jungo Lin wrote:
[snip]
> > >                 dev_dbg(cam->dev, "jobs are full\n");
> > >                 spin_unlock_irqrestore(&cam->pending_job_lock, flags);
> > >                 return;
> > >         }
> > >         list_for_each_entry_safe(req, req_prev, &cam->pending_job_list, list) {
> >
> > Could we instead check the counter here and break if it's >=
> > MTK_ISP_MAX_RUNNING_JOBS?
> > Then we could increment it here too to simplify the code.
> >
>
> Thanks for your advice.
> We simplified this function as below:
>
> void mtk_cam_dev_req_try_queue(struct mtk_cam_dev *cam)
> {
>         struct mtk_cam_dev_request *req, *req_prev;
>         unsigned long flags;
>
>         if (!cam->streaming) {
>                 dev_dbg(cam->dev, "stream is off\n");
>                 return;
>         }
>
>         spin_lock_irq(&cam->pending_job_lock);
>         spin_lock_irqsave(&cam->running_job_lock, flags);

Having the inner call spin_lock_irqsave() doesn't really do anything
useful, because the outer spin_lock_irq() disables the IRQs and flags
would always have the IRQ disabled state. Please use irqsave for the
outer call.

[snip]
> > > > > > > +
> > > > > > > +static struct v4l2_subdev *
> > > > > > > +mtk_cam_cio_get_active_sensor(struct mtk_cam_dev *cam_dev)
> > > > > > > +{
> > > > > > > +   struct media_device *mdev = cam_dev->seninf->entity.graph_obj.mdev;
> > > > > > > +   struct media_entity *entity;
> > > > > > > +   struct device *dev = &cam_dev->pdev->dev;
> > > > > > > +   struct v4l2_subdev *sensor;
> > > > > >
> > > > > > This variable would be unitialized if there is no streaming sensor. Was
> > > > > > there no compiler warning generated for this?
> > > > > >
> > > > >
> > > > > No, there is no compiler warning.
> > > > > But, we will assign sensor to NULL to avoid unnecessary compiler warning
> > > > > with different compiler options.
> > > > >
> > > >
> > > > Thanks. It would be useful if you could check why the compiler you're
> > > > using doesn't show a warning here. We might be missing other
> > > > uninitialized variables.
> > > >
> > >
> > > We will feedback to your project team to check the possible reason about
> > > compiler warning issue.
> > >
> >
> > Do you mean that it was the Clang toolchain used on Chromium OS (e.g.
> > emerge chromeos-kernel-4_19)?
>
> > [snip]
>
> Yes, I checked this comment in the Chromium OS build environment.
> But, I think I have made the mistake here. I need to check the build
> status in the Mediatek's kernel upstream environment. I will pay
> attention in next path set upstream.
>

Thanks a lot. I will recheck this in the Chromium OS toolchain too.

> > > > > > > +
> > > > > > > +   dev_dbg(dev, "%s: node:%d fd:%d idx:%d\n",
> > > > > > > +           __func__,
> > > > > > > +           node->id,
> > > > > > > +           buf->vbb.request_fd,
> > > > > > > +           buf->vbb.vb2_buf.index);
> > > > > > > +
> > > > > > > +   /* For request buffers en-queue, handled in mtk_cam_req_try_queue */
> > > > > > > +   if (vb->vb2_queue->uses_requests)
> > > > > > > +           return;
> > > > > >
> > > > > > I'd suggest removing non-request support from this driver. Even if we end up
> > > > > > with a need to provide compatibility for non-request mode, then it should be
> > > > > > built on top of the requests mode, so that the driver itself doesn't have to
> > > > > > deal with two modes.
> > > > > >
> > > > >
> > > > > The purpose of non-request function in this driver is needed by
> > > > > our camera middle-ware design. It needs 3A statistics buffers before
> > > > > image buffers en-queue. So we need to en-queue 3A statistics with
> > > > > non-request mode in this driver. After MW got the 3A statistics data, it
> > > > > will en-queue the images, tuning buffer and other meta buffers with
> > > > > request mode. Based on this requirement, do you have any suggestion?
> > > > > For upstream driver, should we only consider request mode?
> > > > >
> > > >
> > > > Where does that requirement come from? Why the timing of queuing of
> > > > the buffers to the driver is important?
> > > >
> > > > [snip]
> > >
> > > Basically, this requirement comes from our internal camera
> > > middle-ware/3A hal in user space. Since this is not generic requirement,
> > > we will follow your original suggestion to keep the request mode only
> > > and remove other non-request design in other files. For upstream driver,
> > > it should support request mode only.
> > >
> >
> > Note that Chromium OS will use the "upstream driver" and we don't want
> > to diverge, so please make the userspace also use only requests. I
> > don't see a reason why there would be any need to submit any buffers
> > outside of a request.
> >
> > [snip]
>
> Ok, I have raised your concern to our colleagues and let him to discuss
> with you in another communication channel.
>

Thanks!

Best regards,
Tomasz