[PATCH v3 02/10] mtd: powernv_flash: Lock around concurrent access to OPAL

[Cyril Bur <cyrilbur@gmail.com>]

OPAL can only manage one flash access at a time and will return an
OPAL_BUSY error for each concurrent access to the flash. The simplest
way to prevent this from happening is with a mutex.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
---
 drivers/mtd/devices/powernv_flash.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/devices/powernv_flash.c b/drivers/mtd/devices/powernv_flash.c
index a9a20c00687c..7b41af06f4fe 100644
--- a/drivers/mtd/devices/powernv_flash.c
+++ b/drivers/mtd/devices/powernv_flash.c
@@ -38,6 +38,7 @@
 
 struct powernv_flash {
 	struct mtd_info	mtd;
+	struct mutex lock;
 	u32 id;
 };
 
@@ -59,12 +60,15 @@ static int powernv_flash_async_op(struct mtd_info *mtd, enum flash_op op,
 	dev_dbg(dev, "%s(op=%d, offset=0x%llx, len=%zu)\n",
 			__func__, op, offset, len);
 
+	mutex_lock(&info->lock);
+
 	token = opal_async_get_token_interruptible();
 	if (token < 0) {
 		if (token != -ERESTARTSYS)
 			dev_err(dev, "Failed to get an async token\n");
 
-		return token;
+		rc = token;
+		goto out;
 	}
 
 	switch (op) {
@@ -79,18 +83,21 @@ static int powernv_flash_async_op(struct mtd_info *mtd, enum flash_op op,
 		break;
 	default:
 		WARN_ON_ONCE(1);
-		return -EIO;
+		rc = -EIO;
+		goto out;
 	}
 
 	if (rc != OPAL_ASYNC_COMPLETION) {
 		dev_err(dev, "opal_flash_async_op(op=%d) failed (rc %d)\n",
 				op, rc);
 		opal_async_release_token(token);
-		return -EIO;
+		rc = -EIO;
+		goto out;
 	}
 
 	rc = opal_async_wait_response(token, &msg);
 	opal_async_release_token(token);
+	mutex_unlock(&info->lock);
 	if (rc) {
 		dev_err(dev, "opal async wait failed (rc %d)\n", rc);
 		return -EIO;
@@ -106,6 +113,9 @@ static int powernv_flash_async_op(struct mtd_info *mtd, enum flash_op op,
 	}
 
 	return rc;
+out:
+	mutex_unlock(&info->lock);
+	return rc;
 }
 
 /**
@@ -237,6 +247,8 @@ static int powernv_flash_probe(struct platform_device *pdev)
 	if (ret)
 		goto out;
 
+	mutex_init(&data->lock);
+
 	dev_set_drvdata(dev, data);
 
 	/*
-- 
2.13.2