Re: [RFC PATCH V1 6/6] platform: mtk-isp: Add Mediatek DIP driver

Frederic Chen
2019-06-11T08:48:06Z

Dear Tomasz,

I'd like to elaborate more about the tuning_data.va.
Would you like to give us some advice about our improvement proposal inline?

Thank you very much.

On Wed, 2019-05-22 at 03:14 +0800, Frederic Chen wrote:
> Dear Tomasz,
>
> I appreciate your comment. It is very helpful for us.
>
>
> > > diff --git a/drivers/media/platform/mtk-isp/isp_50/dip/mtk_dip-sys.c b/drivers/media/platform/mtk-isp/isp_50/dip/mtk_dip-sys.c
> > > new file mode 100644
> > > index 000000000000..54d2b5f5b802
> > > --- /dev/null
> > > +++ b/drivers/media/platform/mtk-isp/isp_50/dip/mtk_dip-sys.c
> > > @@ -0,0 +1,1384 @@

[snip]

> > > +static void dip_submit_worker(struct work_struct *work)
> > > +{
> > > + struct mtk_dip_hw_submit_work *dip_submit_work =
> > > + container_of(work, struct mtk_dip_hw_submit_work, frame_work);
> > > + struct mtk_dip_hw *dip_hw = dip_submit_work->dip_hw;
> > > + struct mtk_dip_dev *dip_dev = mtk_dip_hw_to_dev(dip_hw);
> > > + struct mtk_dip_hw_work *dip_work;
> > > + struct mtk_dip_hw_subframe *buf;
> > > + u32 len, num;
> > > + int ret;
> > > +
> > > + num = atomic_read(&dip_hw->num_composing);
> > > +
> > > + mutex_lock(&dip_hw->dip_worklist.queuelock);
> > > + dip_work = list_first_entry(&dip_hw->dip_worklist.queue,

[snip]

> > > +
> > > + if (dip_work->frameparams.tuning_data.pa == 0) {
> > > + dev_dbg(&dip_dev->pdev->dev,
> > > + "%s: frame_no(%d) has no tuning_data\n",
> > > + __func__, dip_work->frameparams.frame_no);
> > > +
> > > + memcpy(&dip_work->frameparams.tuning_data,
> > > + &buf->tuning_buf, sizeof(buf->tuning_buf));
> >
> > Ditto.
> >
>
> I got it.
>
> > > + memset((char *)buf->tuning_buf.va, 0, DIP_TUNING_SZ);
> >
> > Ditto.
>
> I got it.
>
> >
> > > + /*
> > > + * When user enqueued without tuning buffer,
> > > + * it would use driver internal buffer.
> > > + * So, tuning_data.va should be 0
> > > + */
> > > + dip_work->frameparams.tuning_data.va = 0;
> >
> > I don't understand this. We just zeroed the buffer via this kernel VA few
> > lines above, so why would it have to be set to 0?
> >
>
> I will remove this unnecessary line.
>
> > > + }

After confirming the firmware part, I found that we use this field
(tuning_data.va) to notify firmware if there is no tuning data from
user.

- frameparams.tuning_data.va is 0: use the default tuning data in
SCP, but we still need to pass
frameparams.tuning_data.pa because
the buffer contains some working
buffer required.
- frameparams.tuning_data.va is not 0: the tuning data was passed from
the user

Since we should not pass cpu addres to SCP, could I rename tuning_data.va
as tuning_data.cookie, and write a constant value to indicate if SCP
should use its internal default setting or not here?

For example,
/* SCP uses tuning data passed from userspace*/
dip_work->frameparams.tuning_data.cookie = MTK_DIP_USER_TUNING_DATA;

/* SCP uses internal tuning data */
dip_work->frameparams.tuning_data.cookie = MTK_DIP_DEFAULT_TUNING_DATA;

> > > +
> > > + dip_work->frameparams.drv_data = (u64)dip_hw;
> >
> > Passing kernel pointers to firmware?
>
> I will remove this line.
>
> >
> > > + dip_work->frameparams.state = FRAME_STATE_COMPOSING;
> > > +
> > > + memcpy((void *)buf->frameparam.va, &dip_work->frameparams,
> > > + sizeof(dip_work->frameparams));
> >
> > There shouldn't be a need to type cast the pointer.
> >
>
> I will fix it.
>
> > > +
> > > + dip_send(dip_hw->vpu_pdev, SCP_IPI_DIP_FRAME,
> > > + (void *)&dip_work->frameparams,
> >

[snip]

Sincerely,

Frederic Chen