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 <a.hajda@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

1 files changed, 77 insertions, 1 deletions

diff --git a/drivers/gpu/drm/exynos/exynos5433_drm_decon.c b/drivers/gpu/drm/exynos/exynos5433_drm_decon.c
index 2130ccf1e036..cfe6f8af849f 100644
--- a/drivers/gpu/drm/exynos/exynos5433_drm_decon.c
+++ b/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;