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From:   Yannick Fertre <yannick.fertre@st.com>
To:     Yannick Fertre <yannick.fertre@st.com>,
        Philippe Cornu <philippe.cornu@st.com>,
        Benjamin Gaignard <benjamin.gaignard@st.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        <dri-devel@lists.freedesktop.org>,
        <linux-stm32@st-md-mailman.stormreply.com>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>
Subject: [PATCH] drm/stm: ltdc: enable/disable depends on encoder
Date:   Mon, 20 Jan 2020 14:46:53 +0100
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From: Yannick Fertré <yannick.fertre@st.com>

When connected to a dsi host, the ltdc display controller
must send frames only after the end of the dsi panel
initialization to avoid errors when the dsi host sends
commands to the dsi panel (dsi px fifo full).
To avoid this issue, the display controller must be
enabled/disabled when the encoder is enabled/disabled.

Signed-off-by: Yannick Fertré <yannick.fertre@st.com>
---
 drivers/gpu/drm/stm/ltdc.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 719dfc5..9ef125d 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -437,9 +437,6 @@ static void ltdc_crtc_atomic_enable(struct drm_crtc *crtc,
 	/* Commit shadow registers = update planes at next vblank */
 	reg_set(ldev->regs, LTDC_SRCR, SRCR_VBR);
 
-	/* Enable LTDC */
-	reg_set(ldev->regs, LTDC_GCR, GCR_LTDCEN);
-
 	drm_crtc_vblank_on(crtc);
 }
 
@@ -453,9 +450,6 @@ static void ltdc_crtc_atomic_disable(struct drm_crtc *crtc,
 
 	drm_crtc_vblank_off(crtc);
 
-	/* disable LTDC */
-	reg_clear(ldev->regs, LTDC_GCR, GCR_LTDCEN);
-
 	/* disable IRQ */
 	reg_clear(ldev->regs, LTDC_IER, IER_RRIE | IER_FUIE | IER_TERRIE);
 
@@ -1058,9 +1052,13 @@ static const struct drm_encoder_funcs ltdc_encoder_funcs = {
 static void ltdc_encoder_disable(struct drm_encoder *encoder)
 {
 	struct drm_device *ddev = encoder->dev;
+	struct ltdc_device *ldev = ddev->dev_private;
 
 	DRM_DEBUG_DRIVER("\n");
 
+	/* Disable LTDC */
+	reg_clear(ldev->regs, LTDC_GCR, GCR_LTDCEN);
+
 	/* Set to sleep state the pinctrl whatever type of encoder */
 	pinctrl_pm_select_sleep_state(ddev->dev);
 }
@@ -1068,6 +1066,7 @@ static void ltdc_encoder_disable(struct drm_encoder *encoder)
 static void ltdc_encoder_enable(struct drm_encoder *encoder)
 {
 	struct drm_device *ddev = encoder->dev;
+	struct ltdc_device *ldev = ddev->dev_private;
 
 	DRM_DEBUG_DRIVER("\n");
 
@@ -1078,6 +1077,9 @@ static void ltdc_encoder_enable(struct drm_encoder *encoder)
 	 */
 	if (encoder->encoder_type == DRM_MODE_ENCODER_DPI)
 		pinctrl_pm_select_default_state(ddev->dev);
+
+	/* Enable LTDC */
+	reg_set(ldev->regs, LTDC_GCR, GCR_LTDCEN);
 }
 
 static const struct drm_encoder_helper_funcs ltdc_encoder_helper_funcs = {
-- 
2.7.4