linux-kernel - [PATCH v4 12/78] drm/vc4: crtc: Enable and disable the PV in atomic

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Date:   Wed,  8 Jul 2020 19:41:20 +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 v4 12/78] drm/vc4: crtc: Enable and disable the PV in atomic_enable / disable

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.

Signed-off-by: Maxime Ripard <maxime@...no.tech>
---
 drivers/gpu/drm/vc4/vc4_crtc.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index cdeaa0cd981f..fe2e5675aed4 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -332,9 +332,7 @@ static void vc4_crtc_config_pv(struct drm_crtc *crtc)
 		   PV_CONTROL_TRIGGER_UNDERFLOW |
 		   PV_CONTROL_WAIT_HSTART |
 		   VC4_SET_FIELD(vc4_encoder->clock_select,
-				 PV_CONTROL_CLK_SELECT) |
-		   PV_CONTROL_FIFO_CLR |
-		   PV_CONTROL_EN);
+				 PV_CONTROL_CLK_SELECT));
 }
 
 static void vc4_crtc_mode_set_nofb(struct drm_crtc *crtc)
@@ -386,6 +384,8 @@ static void vc4_crtc_atomic_disable(struct drm_crtc *crtc,
 	ret = wait_for(!(CRTC_READ(PV_V_CONTROL) & PV_VCONTROL_VIDEN), 1);
 	WARN_ONCE(ret, "Timeout waiting for !PV_VCONTROL_VIDEN\n");
 
+	CRTC_WRITE(PV_CONTROL, CRTC_READ(PV_CONTROL) & ~PV_CONTROL_EN);
+
 	vc4_hvs_atomic_disable(crtc, old_state);
 
 	/*
@@ -410,6 +410,10 @@ static void vc4_crtc_atomic_enable(struct drm_crtc *crtc,
 
 	require_hvs_enabled(dev);
 
+	/* Reset the PV fifo. */
+	CRTC_WRITE(PV_CONTROL, CRTC_READ(PV_CONTROL) |
+		   PV_CONTROL_FIFO_CLR | PV_CONTROL_EN);
+
 	/* Enable vblank irq handling before crtc is started otherwise
 	 * drm_crtc_get_vblank() fails in vc4_crtc_update_dlist().
 	 */
-- 
git-series 0.9.1