Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver

[Sowjanya Komatineni]

On 4/5/20 1:35 PM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
>
>
> 04.04.2020 04:25, Sowjanya Komatineni ÐÐÑÐÑ:
> ...
> > +static int tegra_channel_capture_frame(struct tegra_vi_channel *chan,
> > +                                    struct tegra_channel_buffer *buf)
> > +{
> > +     int err = 0;
> > +     u32 thresh, value, frame_start, mw_ack_done;
> > +     int bytes_per_line = chan->format.bytesperline;
> > +
> > +     /* program buffer address by using surface 0 */
> > +     vi_csi_write(chan, TEGRA_VI_CSI_SURFACE0_OFFSET_MSB,
> > +                  (u64)buf->addr >> 32);
> > +     vi_csi_write(chan, TEGRA_VI_CSI_SURFACE0_OFFSET_LSB, buf->addr);
> > +     vi_csi_write(chan, TEGRA_VI_CSI_SURFACE0_STRIDE, bytes_per_line);
> > +
> > +     /*
> > +      * Tegra VI block interacts with host1x syncpt for synchronizing
> > +      * programmed condition of capture state and hardware operation.
> > +      * Frame start and Memory write acknowledge syncpts has their own
> > +      * FIFO of depth 2.
> > +      *
> > +      * Syncpoint trigger conditions set through VI_INCR_SYNCPT register
> > +      * are added to HW syncpt FIFO and when the HW triggers, syncpt
> > +      * condition is removed from the FIFO and counter at syncpoint index
> > +      * will be incremented by the hardware and software can wait for
> > +      * counter to reach threshold to synchronize capturing frame with the
> > +      * hardware capture events.
> > +      */
> > +
> > +     /* increase channel syncpoint threshold for FRAME_START */
> > +     thresh = host1x_syncpt_incr_max(chan->frame_start_sp, 1);
> > +
> > +     /* Program FRAME_START trigger condition syncpt request */
> > +     frame_start = VI_CSI_PP_FRAME_START(chan->portno);
> > +     value = VI_CFG_VI_INCR_SYNCPT_COND(frame_start) |
> > +             host1x_syncpt_id(chan->frame_start_sp);
> > +     tegra_vi_write(chan, TEGRA_VI_CFG_VI_INCR_SYNCPT, value);
> > +
> > +     /* increase channel syncpoint threshold for MW_ACK_DONE */
> > +     buf->mw_ack_sp_thresh = host1x_syncpt_incr_max(chan->mw_ack_sp, 1);
> > +
> > +     /* Program MW_ACK_DONE trigger condition syncpt request */
> > +     mw_ack_done = VI_CSI_MW_ACK_DONE(chan->portno);
> > +     value = VI_CFG_VI_INCR_SYNCPT_COND(mw_ack_done) |
> > +             host1x_syncpt_id(chan->mw_ack_sp);
> > +     tegra_vi_write(chan, TEGRA_VI_CFG_VI_INCR_SYNCPT, value);
> > +
> > +     /* enable single shot capture */
> > +     vi_csi_write(chan, TEGRA_VI_CSI_SINGLE_SHOT, SINGLE_SHOT_CAPTURE);
> > +     chan->capture_reqs++;
> > +
> > +     /* wait for syncpt counter to reach frame start event threshold */
> > +     err = host1x_syncpt_wait(chan->frame_start_sp, thresh,
> > +                              TEGRA_VI_SYNCPT_WAIT_TIMEOUT, &value);
> > +     if (err) {
> > +             dev_err(&chan->video.dev,
> > +                     "frame start syncpt timeout: %d\n", err);
> > +             /* increment syncpoint counter for timedout events */
> > +             host1x_syncpt_incr(chan->frame_start_sp);
> Why incrementing is done while hardware is still active?
>
> The sync point's state needs to be completely reset after resetting
> hardware. But I don't think that the current upstream host1x driver
> supports doing that, it's one of the known-long-standing problems of the
> host1x driver.
>
> At least the sp->max_val incrementing should be done based on the actual
> syncpoint value and this should be done after resetting hardware.

upstream host1x driver don't have API to reset or to equalize max value 
with min/load value.

So to synchronize missed event, incrementing HW syncpt counter.

This should not impact as we increment this in case of missed events only.

> > +             spin_lock(&chan->sp_incr_lock);
> > +             host1x_syncpt_incr(chan->mw_ack_sp);
> > +             spin_unlock(&chan->sp_incr_lock);
> > +             /* clear errors and recover */
> > +             tegra_channel_capture_error_recover(chan);
> > +             release_buffer(chan, buf, VB2_BUF_STATE_ERROR);
> > +             return err;
> > +     }