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    SubjectRe: [PATCH v3 032/105] drm/vc4: crtc: Enable and disable the PV in atomic_enable / disable
    On Tue, Jun 2, 2020 at 8:02 AM Dave Stevenson
    <dave.stevenson@raspberrypi.com> wrote:
    >
    > Hi Maxime and Eric
    >
    > On Tue, 2 Jun 2020 at 15:12, Maxime Ripard <maxime@cerno.tech> wrote:
    > >
    > > Hi Eric
    > >
    > > On Wed, May 27, 2020 at 09:54:44AM -0700, Eric Anholt wrote:
    > > > On Wed, May 27, 2020 at 8:50 AM Maxime Ripard <maxime@cerno.tech> wrote:
    > > > >
    > > > > The VIDEN bit in the pixelvalve currently being used to enable or disable
    > > > > the pixelvalve seems to not be enough in some situations, which whill end
    > > > > up with the pixelvalve stalling.
    > > > >
    > > > > In such a case, even re-enabling VIDEN doesn't bring it back and we need to
    > > > > clear the FIFO. This can only be done if the pixelvalve is disabled though.
    > > > >
    > > > > In order to overcome this, we can configure the pixelvalve during
    > > > > mode_set_no_fb, but only enable it in atomic_enable and flush the FIFO
    > > > > there, and in atomic_disable disable the pixelvalve again.
    > > >
    > > > What displays has this been tested with? Getting this sequencing
    > > > right is so painful, and things like DSI are tricky to get to light
    > > > up.
    > >
    > > That FIFO is between the HVS and the HDMI PVs, so this was obviously
    > > tested against that. Dave also tested the DSI output IIRC, so we should
    > > be covered here.
    >
    > DSI wasn't working on the first patch set that Maxime sent - I haven't
    > tested this one as yet but will do so.
    > DPI was working early on to both an Adafruit 800x480 DPI panel, and
    > via a VGA666 as VGA.
    > HDMI is obviously working.
    > VEC is being ignored now. The clock structure is more restricted than
    > earlier chips, so to get the required clocks for the VEC without using
    > fractional divides it compromises the clock that other parts of the
    > system can run at (IIRC including the ARM). That's why the VEC has to
    > be explicitly enabled for the firmware to enable it as the only
    > output. It's annoying, but that's just a restriction of the chip.

    I'm more concerned with "make sure we don't regress pre-pi4 with this
    series" than "pi4 displays all work from the beginning"

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