drm/stm: ltdc: add per plane update support

Recent ltdc hardware versions offer the ability
to update a plane independently of others planes.
This is could be useful especially if a plane is
assigned to another OS.
Signed-off-by: Yannick Fertre <yannick.fertre@foss.st.com>
Acked-by: Philippe Cornu <philippe.cornu@foss.st.com>
Reviewed-by: Philippe Cornu <philippe.cornu@foss.st.com>
Reviewed-by: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>
Signed-off-by: Philippe Cornu <philippe.cornu@foss.st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211215214817.20310-1-yannick.fertre@foss.st.com

drivers/gpu/drm/stm/ltdc.c

@@ -197,6 +197,10 @@
 
 #define LXCFBLNR_CFBLN	GENMASK(10, 0)	/* Color Frame Buffer Line Number */
 
+#define LXRCR_IMR	BIT(0)		/* IMmediate Reload */
+#define LXRCR_VBR	BIT(1)		/* Vertical Blanking Reload */
+#define LXRCR_GRMSK	BIT(2)		/* Global (centralized) Reload MaSKed */
+
 #define CLUT_SIZE	256
 
 #define CONSTA_MAX	0xFF		/* CONSTant Alpha MAX= 1.0 */
@@ -534,7 +538,8 @@ static void ltdc_crtc_atomic_enable(struct drm_crtc *crtc,
 	regmap_set_bits(ldev->regmap, LTDC_IER, IER_RRIE | IER_FUIE | IER_TERRIE);
 
 	/* Commit shadow registers = update planes at next vblank */
-	regmap_set_bits(ldev->regmap, LTDC_SRCR, SRCR_VBR);
+	if (!ldev->caps.plane_reg_shadow)
+		regmap_set_bits(ldev->regmap, LTDC_SRCR, SRCR_VBR);
 
 	drm_crtc_vblank_on(crtc);
 }
@@ -553,7 +558,8 @@ static void ltdc_crtc_atomic_disable(struct drm_crtc *crtc,
 	regmap_clear_bits(ldev->regmap, LTDC_IER, IER_RRIE | IER_FUIE | IER_TERRIE);
 
 	/* immediately commit disable of layers before switching off LTDC */
-	regmap_set_bits(ldev->regmap, LTDC_SRCR, SRCR_IMR);
+	if (!ldev->caps.plane_reg_shadow)
+		regmap_set_bits(ldev->regmap, LTDC_SRCR, SRCR_IMR);
 
 	pm_runtime_put_sync(ddev->dev);
 }
@@ -769,7 +775,8 @@ static void ltdc_crtc_atomic_flush(struct drm_crtc *crtc,
 	ltdc_crtc_update_clut(crtc);
 
 	/* Commit shadow registers = update planes at next vblank */
-	regmap_set_bits(ldev->regmap, LTDC_SRCR, SRCR_VBR);
+	if (!ldev->caps.plane_reg_shadow)
+		regmap_set_bits(ldev->regmap, LTDC_SRCR, SRCR_VBR);
 
 	if (event) {
 		crtc->state->event = NULL;
@@ -1010,6 +1017,11 @@ static void ltdc_plane_atomic_update(struct drm_plane *plane,
 	val |= LXCR_LEN;
 	regmap_write_bits(ldev->regmap, LTDC_L1CR + lofs, LXCR_LEN | LXCR_CLUTEN, val);
 
+	/* Commit shadow registers = update plane at next vblank */
+	if (ldev->caps.plane_reg_shadow)
+		regmap_write_bits(ldev->regmap, LTDC_L1RCR + lofs,
+				  LXRCR_IMR | LXRCR_VBR | LXRCR_GRMSK, LXRCR_VBR);
+
 	ldev->plane_fpsi[plane->index].counter++;
 
 	mutex_lock(&ldev->err_lock);
@@ -1035,6 +1047,11 @@ static void ltdc_plane_atomic_disable(struct drm_plane *plane,
 	/* disable layer */
 	regmap_write_bits(ldev->regmap, LTDC_L1CR + lofs, LXCR_LEN, 0);
 
+	/* Commit shadow registers = update plane at next vblank */
+	if (ldev->caps.plane_reg_shadow)
+		regmap_write_bits(ldev->regmap, LTDC_L1RCR + lofs,
+				  LXRCR_IMR | LXRCR_VBR | LXRCR_GRMSK, LXRCR_VBR);
+
 	DRM_DEBUG_DRIVER("CRTC:%d plane:%d\n",
 			 oldstate->crtc->base.id, plane->base.id);
 }
@@ -1307,6 +1324,7 @@ static int ltdc_get_caps(struct drm_device *ddev)
 			ldev->caps.pad_max_freq_hz = 65000000;
 		ldev->caps.nb_irq = 2;
 		ldev->caps.ycbcr_output = false;
+		ldev->caps.plane_reg_shadow = false;
 		break;
 	case HWVER_20101:
 		ldev->caps.layer_ofs = LAY_OFS_0;
@@ -1316,6 +1334,7 @@ static int ltdc_get_caps(struct drm_device *ddev)
 		ldev->caps.pad_max_freq_hz = 150000000;
 		ldev->caps.nb_irq = 4;
 		ldev->caps.ycbcr_output = false;
+		ldev->caps.plane_reg_shadow = false;
 		break;
 	case HWVER_40100:
 		ldev->caps.layer_ofs = LAY_OFS_1;
@@ -1325,6 +1344,7 @@ static int ltdc_get_caps(struct drm_device *ddev)
 		ldev->caps.pad_max_freq_hz = 90000000;
 		ldev->caps.nb_irq = 2;
 		ldev->caps.ycbcr_output = true;
+		ldev->caps.plane_reg_shadow = true;
 		break;
 	default:
 		return -ENODEV;

drivers/gpu/drm/stm/ltdc.h

@@ -22,6 +22,7 @@ struct ltdc_caps {
 	int pad_max_freq_hz;	/* max frequency supported by pad */
 	int nb_irq;		/* number of hardware interrupts */
 	bool ycbcr_output;	/* ycbcr output converter supported */
+	bool plane_reg_shadow;	/* plane shadow registers ability */
 };
 
 #define LTDC_MAX_LAYER	4