[PATCH v3 2/2] fpga: altera-cvp: Retry teardown and reset CVP state on failure

[muhammad . nazim . amirul . nazle . asmade]

From: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@xxxxxxxxxx>

The driver polls CFG_RDY for 0 as notification that the endpoint has
finished teardown and a new session can start safely. After a bad
bitstream that poll can time out: CFG_RDY may stay stuck when
HIP_CLK_SEL=0 if the device has already left usermode before the poll.

Retrying teardown alone is not enough. Exit CvP mode and switch the HIP
clock that feeds CFG_RDY so CVP_STATUS becomes responsive again, then
try the teardown once more.

Introduce altera_cvp_recovery() to wrap this cleanup and single retry.

Signed-off-by: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@xxxxxxxxxx>
---
 drivers/fpga/altera-cvp.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/drivers/fpga/altera-cvp.c b/drivers/fpga/altera-cvp.c
index 559191180825..549e0ce1545f 100644
--- a/drivers/fpga/altera-cvp.c
+++ b/drivers/fpga/altera-cvp.c
@@ -316,7 +316,29 @@ static int altera_cvp_teardown(struct fpga_manager *mgr,
 	ret = altera_cvp_wait_status(conf, VSE_CVP_STATUS_CFG_RDY, 0,
 				     conf->priv->poll_time_us);
 	if (ret)
-		dev_err(&mgr->dev, "CFG_RDY == 0 timeout\n");
+		dev_warn(&mgr->dev, "CFG_RDY == 0 timeout\n");
+
+	return ret;
+}
+
+static int altera_cvp_recovery(struct fpga_manager *mgr,
+			       struct fpga_image_info *info)
+{
+	struct altera_cvp_conf *conf = mgr->priv;
+	int ret;
+
+	ret = altera_cvp_teardown(mgr, info);
+	if (ret) {
+		/*
+		 * CVP_STATUS may get stuck if the device left user mode
+		 * before the poll. Exit CvP mode to switch back the clock
+		 * feeding CVP_STATUS, then try the teardown again.
+		 */
+		altera_cvp_disable_cvp_mode(conf);
+		ret = altera_cvp_teardown(mgr, info);
+		if (ret)
+			dev_err(&mgr->dev, "Tear-down failed\n");
+	}
 
 	return ret;
 }
@@ -353,7 +375,7 @@ static int altera_cvp_write_init(struct fpga_manager *mgr,
 
 	if (val & VSE_CVP_STATUS_CFG_RDY) {
 		dev_warn(&mgr->dev, "CvP already started, tear down first\n");
-		ret = altera_cvp_teardown(mgr, info);
+		ret = altera_cvp_recovery(mgr, info);
 		if (ret)
 			return ret;
 	}
@@ -494,7 +516,7 @@ static int altera_cvp_write_complete(struct fpga_manager *mgr,
 	u32 mask, val;
 	int ret;
 
-	ret = altera_cvp_teardown(mgr, info);
+	ret = altera_cvp_recovery(mgr, info);
 	if (ret)
 		return ret;
 
-- 
2.43.7