Re: LP-11 Timeout on RZ/G2 with ov5640

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Hello
G
On Thu, Nov 25, 2021 at 09:23:41AM +0200, Sakari Ailus wrote:
> Hi Laurent,
>
> On Thu, Nov 25, 2021 at 12:12:18AM +0200, Laurent Pinchart wrote:
> > Hi Adam,
> >
> > (CC'ing Sakari)
> >
> > On Wed, Nov 24, 2021 at 03:16:57PM -0600, Adam Ford wrote:
> > > I am trying to use an OV5640 camera sensor that I've used on both an
> > > i.MX6Q and an i.MX8M Mini (with good success) on an RZ/G2[MNH] board
> > > connected to the 2-lane CSI interface.
> > >
> > > I can get the media-ctl to show the routings, and sometimes I can get
> > > streaming.  Often, I get a timeout:
> > >
> > >      rcar-csi2 fea80000.csi2: Timeout waiting for LP-11 state
> > >
> > > Looking at the various mailing list e-mails for the LP-11, it's
> > > unclear to me if the timeout is caused by the sensor not doing
> > > something correctly or the CSI2 misbehaving.
> >
> > Before transitioning to the high speed (HS) mode, the D-PHY transmitter
> > must drive the lane in the LP-11 state. This is the idle state of the
> > lane when powered up and when not in the ultra low-power state (ULPS).
> > The transition to HS mode on the receiver side involves observing the
> > LP-11 state. Many D-PHY RX require configuring the PHY when the lane is
> > in LP-11 state, and only then starting the sensor to transition to HS.
> > This requires powering up the D-PHY TX and going to idle mode, which
> > most sensors support. As we're deprecating the .s_power() subdev
> > operation, however, we have no way to power up the sensor without
> > starting it before the D-PHY RX gets configured.
>
> That's not true anymore. Please see:
>
> <URL:https://hverkuil.home.xs4all.nl/spec/driver-api/tx-rx.html#lp-11-and-lp-111-modes>
>
> Not all sensors can do this without tricks though.
>
> >
> > In some cases, the D-PHY RX can handle the power up sequence
> > automatically. They can be fully configured (from a software point of
> > view) while the lane is in the power down state LP-00, and they then
> > handle the transition to the stop state LP-11 and to the HS mode
> > automatically. This isn't true for all receivers, some need software
> > configuration after the data lane reaches the LP-11 state and before it
> > transitions to HS mode. According to the documentation, the R-Car CSI-2
> > receiver requires software intervention between LP-11 and HS mode at
> > least on V3M and E3. There's also a software configuration step on H3,
> > M3N, V3H and V3U, but there's a chance that one could possibly be
> > bypassed.
> >
> > > I was hoping someone might have some suggestions of things I can try.
> >
> > I would first try to power up the sensor at probe time and keep it power
> > forever, to see if it solves your issue. If it does, then introducing a
> > CSI-2-specific subdev operation to power up the sensor (or officially
> > de-deprecating .s_power() for this use case) could be an option to fix
> > the issue properly.

What about .pre_streamon video op ?
Should it fit here ?


>
> --
> Kind regards,
>
> Sakari Ailus



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