On Tue, 2017-01-31 at 00:01 +0000, Russell King - ARM Linux wrote:
[...]

The iMX6 manuals call for a very specific seven sequence of initialisation
for CSI2, which begins with:

1. reset the D-PHY.
2. place MIPI sensor in LP-11 state
3. perform D-PHY initialisation
4. configure CSI2 lanes and de-assert resets and shutdown signals

Since you reset the CSI2 at power up and then release it, how do you
guarantee that the published sequence is followed?

With Philipp's driver, this is easy, because there is a prepare_stream
callback which gives the sensor an opportunity to get everything
correctly configured according to the negotiated parameters, and place
the sensor in LP-11 state.

Some sensors do not power up in LP-11 state, but need to be programmed
fully before being asked to momentarily stream.  Only at that point is
the sensor guaranteed to be in the required LP-11 state.

Do you expect that 1. and 2. could depend on the negotiated parameters
in any way on some hardware? I had removed the prepare_stream callback
from my driver in v2 because for my use case at least the above sequence
could be realized by

1. in imx-mipi-csi2 s_power(1)
2. in MIPI sensor s_power(1)
3./4. in imx-mipi-csi2 s_stream(1)
4. in MIPI sensor s_stream(1)

as long as the sensor is correctly put back into LP-11 in s_stream(0).

regards
Philipp

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