Hi Laurent,
On 2019-03-12 22:22:01 +0200, Laurent Pinchart wrote:
> Hello Niklas,
>
> On Tue, Mar 12, 2019 at 07:58:13PM +0100, Niklas Söderlund wrote:
> > On 2019-03-11 11:53:01 +0100, Hans Verkuil wrote:
> > > On 2/18/19 11:15 AM, Niklas Söderlund wrote:
> > >> Restart the CSI-2 link if the CSI-2 receiver detects an error during
> > >> reception. The driver did nothing when a link error happened and the
> > >> data flow simply stopped without the user knowing why.
> > >>
> > >> Change the driver to try and recover from errors by restarting the link
> > >> and informing the user that something is not right. For obvious reasons
> > >> it's not possible to recover from all errors (video source disconnected
> > >> for example) but in such cases the user is at least informed of the
> > >> error and the same behavior of the stopped data flow is retained.
>
> What error causes have you noticed in practice that would benefit from
> this ?
In practice I have not manage to produce this error using the ADV748x
which would match a real world use-case. I have however demonstrated
that it works by introducing a small delay between the bottom and top
half of the irq handler and unplugging / replugging the HDMI cable to
trigger the issue and see that it recovers.
>
> > > What you really would like to have is that when a CSI error is detected,
> > > the CSI driver can ask upstream whether or not a disconnect has taken place.
> > >
> > > If that was the case, then there is no point in restarting the CSI.
> > >
> > > While a disconnect is very uncommon for a sensor, it is of course perfectly
> > > normal if an HDMI-to-CSI bridge was connected to the CSI port.
>
> Note that this may not always result in a CSI-2 error, the HDMI to CSI-2
> bridge may continue sending valid timings with dummy (or random) data.
>
> > > Unfortunately, we don't have such functionality, but perhaps this is something
> > > to think about?
> >
> > I think your idea sounds good and that such a functionality could be
> > useful. I have a feeling such a functionality could be related to
> > notifications?
> >
> > > This does mean, however, that I don't like the dev_err since it doesn't have
> > > to be an error. I would suggest replacing the first dev_err by dev_info and
> > > the second by dev_warn.
> >
> > With the background you provides I agree that they should not be
> > dev_err. I will update as you suggest for the next version, thanks.
> >
> > >> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
> > >> ---
> > >> drivers/media/platform/rcar-vin/rcar-csi2.c | 52 ++++++++++++++++++++-
> > >> 1 file changed, 51 insertions(+), 1 deletion(-)
> > >>
> > >> diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
> > >> index f90b380478775015..0506fe4106d5c012 100644
> > >> --- a/drivers/media/platform/rcar-vin/rcar-csi2.c
> > >> +++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
> > >> @@ -84,6 +84,9 @@ struct rcar_csi2;
> > >>
> > >> /* Interrupt Enable */
> > >> #define INTEN_REG 0x30
> > >> +#define INTEN_INT_AFIFO_OF BIT(27)
> > >> +#define INTEN_INT_ERRSOTHS BIT(4)
> > >> +#define INTEN_INT_ERRSOTSYNCHS BIT(3)
> > >>
> > >> /* Interrupt Source Mask */
> > >> #define INTCLOSE_REG 0x34
> > >> @@ -540,6 +543,10 @@ static int rcsi2_start_receiver(struct rcar_csi2 *priv)
> > >> if (mbps < 0)
> > >> return mbps;
> > >>
> > >> + /* Enable interrupts. */
> > >> + rcsi2_write(priv, INTEN_REG, INTEN_INT_AFIFO_OF | INTEN_INT_ERRSOTHS
> > >> + | INTEN_INT_ERRSOTSYNCHS);
> > >> +
> > >> /* Init */
> > >> rcsi2_write(priv, TREF_REG, TREF_TREF);
> > >> rcsi2_write(priv, PHTC_REG, 0);
> > >> @@ -702,6 +709,43 @@ static const struct v4l2_subdev_ops rcar_csi2_subdev_ops = {
> > >> .pad = &rcar_csi2_pad_ops,
> > >> };
> > >>
> > >> +static irqreturn_t rcsi2_irq(int irq, void *data)
> > >> +{
> > >> + struct rcar_csi2 *priv = data;
> > >> + u32 status, err_status;
> > >> +
> > >> + status = rcsi2_read(priv, INTSTATE_REG);
> > >> + err_status = rcsi2_read(priv, INTERRSTATE_REG);
> > >> +
> > >> + if (!status)
> > >> + return IRQ_HANDLED;
> > >> +
> > >> + rcsi2_write(priv, INTSTATE_REG, status);
> > >> +
> > >> + if (!err_status)
> > >> + return IRQ_HANDLED;
> > >> +
> > >> + rcsi2_write(priv, INTERRSTATE_REG, err_status);
> > >> +
> > >> + dev_err(priv->dev, "Transfer error, restarting CSI-2 receiver\n");
> > >> +
> > >> + return IRQ_WAKE_THREAD;
> > >> +}
> > >> +
> > >> +static irqreturn_t rcsi2_irq_thread(int irq, void *data)
> > >> +{
> > >> + struct rcar_csi2 *priv = data;
> > >> +
> > >> + mutex_lock(&priv->lock);
> > >> + rcsi2_stop(priv);
> > >> + usleep_range(1000, 2000);
> > >> + if (rcsi2_start(priv))
> > >> + dev_err(priv->dev, "Failed to restart CSI-2 receiver\n");
> > >> + mutex_unlock(&priv->lock);
> > >> +
> > >> + return IRQ_HANDLED;
> > >> +}
> > >> +
> > >> /* -----------------------------------------------------------------------------
> > >> * Async handling and registration of subdevices and links.
> > >> */
> > >> @@ -982,7 +1026,7 @@ static int rcsi2_probe_resources(struct rcar_csi2 *priv,
> > >> struct platform_device *pdev)
> > >> {
> > >> struct resource *res;
> > >> - int irq;
> > >> + int irq, ret;
> > >>
> > >> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > >> priv->base = devm_ioremap_resource(&pdev->dev, res);
> > >> @@ -993,6 +1037,12 @@ static int rcsi2_probe_resources(struct rcar_csi2 *priv,
> > >> if (irq < 0)
> > >> return irq;
> > >>
> > >> + ret = devm_request_threaded_irq(&pdev->dev, irq, rcsi2_irq,
> > >> + rcsi2_irq_thread, IRQF_SHARED,
> > >> + KBUILD_MODNAME, priv);
> > >> + if (ret)
> > >> + return ret;
> > >> +
> > >> priv->rstc = devm_reset_control_get(&pdev->dev, NULL);
> > >> if (IS_ERR(priv->rstc))
> > >> return PTR_ERR(priv->rstc);
>
> --
> Regards,
>
> Laurent Pinchart
--
Regards,
Niklas Söderlund
