[PATCH v2 3/8] imx-drm: ipu-dmfc: Wait for FIFOs to run empty before disabling

[Philipp Zabel]

Disabling the DMFC module while there is still data in the FIFOs could
cause the "new frame before end of frame" error state when the DMFC is
enabled again.

Signed-off-by: Philipp Zabel <p.zabel at pengutronix.de>
---
 drivers/staging/imx-drm/ipu-v3/ipu-dmfc.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/imx-drm/ipu-v3/ipu-dmfc.c b/drivers/staging/imx-drm/ipu-v3/ipu-dmfc.c
index 4521301..59f182b 100644
--- a/drivers/staging/imx-drm/ipu-v3/ipu-dmfc.c
+++ b/drivers/staging/imx-drm/ipu-v3/ipu-dmfc.c
@@ -28,7 +28,12 @@
 #define DMFC_GENERAL1		0x0014
 #define DMFC_GENERAL2		0x0018
 #define DMFC_IC_CTRL		0x001c
-#define DMFC_STAT		0x0020
+#define DMFC_WR_CHAN_ALT	0x0020
+#define DMFC_WR_CHAN_DEF_ALT	0x0024
+#define DMFC_DP_CHAN_ALT	0x0028
+#define DMFC_DP_CHAN_DEF_ALT	0x002c
+#define DMFC_GENERAL1_ALT	0x0030
+#define DMFC_STAT		0x0034
 
 #define DMFC_WR_CHAN_1_28		0
 #define DMFC_WR_CHAN_2_41		8
@@ -133,6 +138,20 @@ int ipu_dmfc_enable_channel(struct dmfc_channel *dmfc)
 }
 EXPORT_SYMBOL_GPL(ipu_dmfc_enable_channel);
 
+static void ipu_dmfc_wait_fifos(struct ipu_dmfc_priv *priv)
+{
+	unsigned long timeout = jiffies + msecs_to_jiffies(1000);
+
+	while ((readl(priv->base + DMFC_STAT) & 0x02fff000) != 0x02fff000) {
+		if (time_after(jiffies, timeout)) {
+			dev_warn(priv->dev,
+				 "Timeout waiting for DMFC FIFOs to clear\n");
+			break;
+		}
+		cpu_relax();
+	}
+}
+
 void ipu_dmfc_disable_channel(struct dmfc_channel *dmfc)
 {
 	struct ipu_dmfc_priv *priv = dmfc->priv;
@@ -141,8 +160,10 @@ void ipu_dmfc_disable_channel(struct dmfc_channel *dmfc)
 
 	priv->use_count--;
 
-	if (!priv->use_count)
+	if (!priv->use_count) {
+		ipu_dmfc_wait_fifos(priv);
 		ipu_module_disable(priv->ipu, IPU_CONF_DMFC_EN);
+	}
 
 	if (priv->use_count < 0)
 		priv->use_count = 0;
-- 
1.9.1