drm/exynos/decon5433: fix vblank event handling

Current implementation of event handling assumes that vblank interrupt is
always called at the right time. It is not true, it can be delayed due to
various reasons. As a result different races can happen. The patch fixes
the issue by using hardware frame counter present in DECON to serialize
vblank and commit completion events.

Signed-off-by: Andrzej Hajda <[email protected]>
Signed-off-by: Inki Dae <[email protected]>

drivers/gpu/drm/exynos/exynos5433_drm_decon.c

@@ -68,6 +68,8 @@ struct decon_context {
 	unsigned long			flags;
 	unsigned long			out_type;
 	int				first_win;
+	spinlock_t			vblank_lock;
+	u32				frame_id;
 };
 
 static const uint32_t decon_formats[] = {
@@ -122,6 +124,48 @@ static void decon_disable_vblank(struct exynos_drm_crtc *crtc)
 		writel(0, ctx->addr + DECON_VIDINTCON0);
 }
 
+/* return number of starts/ends of frame transmissions since reset */
+static u32 decon_get_frame_count(struct decon_context *ctx, bool end)
+{
+	u32 frm, pfrm, status, cnt = 2;
+
+	/* To get consistent result repeat read until frame id is stable.
+	 * Usually the loop will be executed once, in rare cases when the loop
+	 * is executed at frame change time 2nd pass will be needed.
+	 */
+	frm = readl(ctx->addr + DECON_CRFMID);
+	do {
+		status = readl(ctx->addr + DECON_VIDCON1);
+		pfrm = frm;
+		frm = readl(ctx->addr + DECON_CRFMID);
+	} while (frm != pfrm && --cnt);
+
+	/* CRFMID is incremented on BPORCH in case of I80 and on VSYNC in case
+	 * of RGB, it should be taken into account.
+	 */
+	if (!frm)
+		return 0;
+
+	switch (status & (VIDCON1_VSTATUS_MASK | VIDCON1_I80_ACTIVE)) {
+	case VIDCON1_VSTATUS_VS:
+		if (!(ctx->out_type & IFTYPE_I80))
+			--frm;
+		break;
+	case VIDCON1_VSTATUS_BP:
+		--frm;
+		break;
+	case VIDCON1_I80_ACTIVE:
+	case VIDCON1_VSTATUS_AC:
+		if (end)
+			--frm;
+		break;
+	default:
+		break;
+	}
+
+	return frm;
+}
+
 static void decon_setup_trigger(struct decon_context *ctx)
 {
 	if (!(ctx->out_type & (IFTYPE_I80 | I80_HW_TRG)))
@@ -365,11 +409,14 @@ static void decon_disable_plane(struct exynos_drm_crtc *crtc,
 static void decon_atomic_flush(struct exynos_drm_crtc *crtc)
 {
 	struct decon_context *ctx = crtc->ctx;
+	unsigned long flags;
 	int i;
 
 	if (test_bit(BIT_SUSPENDED, &ctx->flags))
 		return;
 
+	spin_lock_irqsave(&ctx->vblank_lock, flags);
+
 	for (i = ctx->first_win; i < WINDOWS_NR; i++)
 		decon_shadow_protect_win(ctx, i, false);
 
@@ -378,12 +425,18 @@ static void decon_atomic_flush(struct exynos_drm_crtc *crtc)
 
 	if (ctx->out_type & IFTYPE_I80)
 		set_bit(BIT_WIN_UPDATED, &ctx->flags);
+
+	ctx->frame_id = decon_get_frame_count(ctx, true);
+
 	exynos_crtc_handle_event(crtc);
+
+	spin_unlock_irqrestore(&ctx->vblank_lock, flags);
 }
 
 static void decon_swreset(struct decon_context *ctx)
 {
 	unsigned int tries;
+	unsigned long flags;
 
 	writel(0, ctx->addr + DECON_VIDCON0);
 	for (tries = 2000; tries; --tries) {
@@ -401,6 +454,10 @@ static void decon_swreset(struct decon_context *ctx)
 
 	WARN(tries == 0, "failed to software reset DECON\n");
 
+	spin_lock_irqsave(&ctx->vblank_lock, flags);
+	ctx->frame_id = 0;
+	spin_unlock_irqrestore(&ctx->vblank_lock, flags);
+
 	if (!(ctx->out_type & IFTYPE_HDMI))
 		return;
 
@@ -579,6 +636,24 @@ static const struct component_ops decon_component_ops = {
 	.unbind = decon_unbind,
 };
 
+static void decon_handle_vblank(struct decon_context *ctx)
+{
+	u32 frm;
+
+	spin_lock(&ctx->vblank_lock);
+
+	frm = decon_get_frame_count(ctx, true);
+
+	if (frm != ctx->frame_id) {
+		/* handle only if incremented, take care of wrap-around */
+		if ((s32)(frm - ctx->frame_id) > 0)
+			drm_crtc_handle_vblank(&ctx->crtc->base);
+		ctx->frame_id = frm;
+	}
+
+	spin_unlock(&ctx->vblank_lock);
+}
+
 static irqreturn_t decon_irq_handler(int irq, void *dev_id)
 {
 	struct decon_context *ctx = dev_id;
@@ -599,7 +674,7 @@ static irqreturn_t decon_irq_handler(int irq, void *dev_id)
 			    (VIDOUT_INTERLACE_EN_F | VIDOUT_INTERLACE_FIELD_F))
 				return IRQ_HANDLED;
 		}
-		drm_crtc_handle_vblank(&ctx->crtc->base);
+		decon_handle_vblank(ctx);
 	}
 
 out:
@@ -672,6 +747,7 @@ static int exynos5433_decon_probe(struct platform_device *pdev)
 	__set_bit(BIT_SUSPENDED, &ctx->flags);
 	ctx->dev = dev;
 	ctx->out_type = (unsigned long)of_device_get_match_data(dev);
+	spin_lock_init(&ctx->vblank_lock);
 
 	if (ctx->out_type & IFTYPE_HDMI) {
 		ctx->first_win = 1;

include/video/exynos5433_decon.h

@@ -46,6 +46,7 @@
 #define DECON_FRAMEFIFO_STATUS		0x0524
 #define DECON_CMU			0x1404
 #define DECON_UPDATE			0x1410
+#define DECON_CRFMID			0x1414
 #define DECON_UPDATE_SCHEME		0x1438
 #define DECON_VIDCON1			0x2000
 #define DECON_VIDCON2			0x2004
@@ -142,6 +143,13 @@
 #define STANDALONE_UPDATE_F		(1 << 0)
 
 /* DECON_VIDCON1 */
+#define VIDCON1_LINECNT_MASK		(0x0fff << 16)
+#define VIDCON1_I80_ACTIVE		(1 << 15)
+#define VIDCON1_VSTATUS_MASK		(0x3 << 13)
+#define VIDCON1_VSTATUS_VS		(0 << 13)
+#define VIDCON1_VSTATUS_BP		(1 << 13)
+#define VIDCON1_VSTATUS_AC		(2 << 13)
+#define VIDCON1_VSTATUS_FP		(3 << 13)
 #define VIDCON1_VCLK_MASK		(0x3 << 9)
 #define VIDCON1_VCLK_RUN_VDEN_DISABLE	(0x3 << 9)
 #define VIDCON1_VCLK_HOLD		(0x0 << 9)