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    SubjectRe: [PATCH v4 00/36] i.MX Media Driver
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    On Thu, 2017-02-16 at 22:57 +0000, Russell King - ARM Linux wrote:
    > On Thu, Feb 16, 2017 at 02:27:41PM -0800, Steve Longerbeam wrote:
    > >
    > >
    > > On 02/16/2017 02:20 PM, Russell King - ARM Linux wrote:
    > > >On Wed, Feb 15, 2017 at 06:19:02PM -0800, Steve Longerbeam wrote:
    > > >>In version 4:
    > > >
    > > >With this version, I get:
    > > >
    > > >[28762.892053] imx6-mipi-csi2: LP-11 timeout, phy_state = 0x00000000
    > > >[28762.899409] ipu1_csi0: pipeline_set_stream failed with -110
    > > >
    > >
    > > Right, in the imx219, on exit from s_power(), the clock and data lanes
    > > must be placed in the LP-11 state. This has been done in the ov5640 and
    > > tc358743 subdevs.
    >
    > The only way to do that is to enable streaming from the sensor, wait
    > an initialisation time, and then disable streaming, and wait for the
    > current line to finish. There is _no_ other way to get the sensor to
    > place its clock and data lines into LP-11 state.

    I thought going through LP-11 is part of the D-PHY transmitter
    initialization, during the LP->HS wakeup sequence. But then I have no
    access to MIPI specs.
    It is unfortunate that the i.MX6 MIPI CSI-2 core needs software
    assistance here, but could it be possible to trigger that sequence in
    the sensor and then without waiting switching to polling for LP-11 state
    in the i.MX6 MIPI CSI-2 receiver?

    > For that to happen, we need to program the sensor a bit more than we
    > currently do at power on (to a minimal resolution, and setting up the
    > PLLs), and introduce another 4ms on top of the 8ms or so that the
    > runtime resume function already takes.
    >
    > Looking at the SMIA driver, things are worse, and I suspect that it also
    > will not work with the current setup - the SMIA spec shows that the CSI
    > clock and data lines are tristated while the sensor is not streaming,
    > which means they aren't held at a guaranteed LP-11 state, even if that
    > driver momentarily enabled streaming. Hence, Freescale's (or is it
    > Synopsis') requirement may actually be difficult to satisfy.
    >
    > However, I regard runtime PM broken with the current imx-capture setup.
    > At the moment, power is controlled at the sensor by whether the media
    > links are enabled. So, if you have an enabled link coming off the
    > sensor, the sensor will be powered up, whether you're using it or not.
    >
    > Given that the number of applications out there that know about the
    > media subdevs is really quite small, this combination makes having
    > runtime PM in sensor devices completely pointless - they can't sleep
    > as long as they have an enabled link, which could be persistent over
    > many days or weeks.

    regards
    Philipp

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