linux-kernel - Re: [PATCH v4 30/78] drm/vc4: crtc: Clear the PixelValve FIFO on disable

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Date:   Tue, 28 Jul 2020 12:40:23 +0100
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Eric Anholt <eric@...olt.net>,
        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,
        LKML <linux-kernel@...r.kernel.org>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Phil Elwell <phil@...pberrypi.com>
Subject: Re: [PATCH v4 30/78] drm/vc4: crtc: Clear the PixelValve FIFO on disable

Hi Maxime

On Wed, 8 Jul 2020 at 18:43, Maxime Ripard <maxime@...no.tech> wrote:
>
> In order to avoid a stale pixel getting stuck on mode change or a disable
> / enable cycle, we need to make sure to flush the PV FIFO on disable.
>
> Signed-off-by: Maxime Ripard <maxime@...no.tech>

Reviewed-by: Dave Stevenson <dave.stevenson@...pberrypi.com>

> ---
>  drivers/gpu/drm/vc4/vc4_crtc.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
> index 7b178d67187f..13fe0e370fb3 100644
> --- a/drivers/gpu/drm/vc4/vc4_crtc.c
> +++ b/drivers/gpu/drm/vc4/vc4_crtc.c
> @@ -408,8 +408,7 @@ static void vc4_crtc_atomic_disable(struct drm_crtc *crtc,
>         if (vc4_encoder->post_crtc_disable)
>                 vc4_encoder->post_crtc_disable(encoder);
>
> -       CRTC_WRITE(PV_CONTROL, CRTC_READ(PV_CONTROL) & ~PV_CONTROL_EN);
> -
> +       vc4_crtc_pixelvalve_reset(crtc);
>         vc4_hvs_atomic_disable(crtc, old_state);
>
>         if (vc4_encoder->post_crtc_powerdown)
> --
> git-series 0.9.1