linux-kernel - [PATCH v3 053/105] drm/vc4: crtc: Clear the PixelValve FIFO during configuration

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Message-Id: <edcf101ddbf3f710d7e7295ffcedca831ca56a12.1590594512.git-series.maxime@cerno.tech>
Date:   Wed, 27 May 2020 17:48:23 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Eric Anholt <eric@...olt.net>
Cc:     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>,
        Maxime Ripard <maxime@...no.tech>
Subject: [PATCH v3 053/105] drm/vc4: crtc: Clear the PixelValve FIFO during configuration

Even though it's not really clear why we need to flush the PV FIFO during
the configuration even though we started by flushing it, experience shows
that without it we get a stale pixel stuck in the FIFO between the HVS and
the PV.

Signed-off-by: Maxime Ripard <maxime@...no.tech>
---
 drivers/gpu/drm/vc4/vc4_crtc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index 61e0945a8697..ecb3431470dd 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -356,7 +356,7 @@ static void vc4_crtc_config_pv(struct drm_crtc *crtc)
 	if (is_dsi)
 		CRTC_WRITE(PV_HACT_ACT, mode->hdisplay * pixel_rep);
 
-	CRTC_WRITE(PV_CONTROL,
+	CRTC_WRITE(PV_CONTROL, PV_CONTROL_FIFO_CLR |
 		   vc4_crtc_get_fifo_full_level_bits(vc4_crtc, format) |
 		   VC4_SET_FIELD(format, PV_CONTROL_FORMAT) |
 		   VC4_SET_FIELD(pixel_rep - 1, PV_CONTROL_PIXEL_REP) |
-- 
git-series 0.9.1