linux-kernel - Re: [PATCH v3 032/105] drm/vc4: crtc: Enable and disable the PV in atomic

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Date:   Tue, 2 Jun 2020 16:12:28 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Eric Anholt <eric@...olt.net>
Cc:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        linux-rpi-kernel@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Phil Elwell <phil@...pberrypi.com>
Subject: Re: [PATCH v3 032/105] drm/vc4: crtc: Enable and disable the PV in
 atomic_enable / disable

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@...no.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.

Maxime

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