[PATCH v4 10/10] mtd: powernv_flash: Use opal_async_wait_response_interruptible()

[Cyril Bur <cyrilbur@gmail.com>]

The OPAL calls performed in this driver shouldn't be using
opal_async_wait_response() as this performs a wait_event() which, on
long running OPAL calls could result in hung task warnings. wait_event()
prevents timely signal delivery which is also undesirable.

This patch also attempts to quieten down the use of dev_err() when
errors haven't actually occurred and also to return better information up
the stack rather than always -EIO.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
---
 drivers/mtd/devices/powernv_flash.c | 57 +++++++++++++++++++++++--------------
 1 file changed, 35 insertions(+), 22 deletions(-)

diff --git a/drivers/mtd/devices/powernv_flash.c b/drivers/mtd/devices/powernv_flash.c
index 3343d4f5c4f3..42383dbca5a6 100644
--- a/drivers/mtd/devices/powernv_flash.c
+++ b/drivers/mtd/devices/powernv_flash.c
@@ -1,7 +1,7 @@
 /*
  * OPAL PNOR flash MTD abstraction
  *
- * Copyright IBM 2015
+ * Copyright IBM 2015-2017
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -89,33 +89,46 @@ static int powernv_flash_async_op(struct mtd_info *mtd, enum flash_op op,
 		return -EIO;
 	}
 
-	if (rc == OPAL_SUCCESS)
-		goto out_success;
+	if (rc == OPAL_ASYNC_COMPLETION) {
+		rc = opal_async_wait_response_interruptible(token, &msg);
+		if (rc) {
+			/*
+			 * If we return the mtd core will free the
+			 * buffer we've just passed to OPAL but OPAL
+			 * will continue to read or write from that
+			 * memory.
+			 * It may be tempting to ultimately return 0
+			 * if we're doing a read or a write since we
+			 * are going to end up waiting until OPAL is
+			 * done. However, because the MTD core sends
+			 * us the userspace request in chunks, we need
+			 * to it know we've been interrupted.
+			 */
+			rc = -EINTR;
+			if (opal_async_wait_response(token, &msg))
+				dev_err(dev, "opal_async_wait_response() failed\n");
+			goto out;
+		}
+		rc = opal_get_async_rc(msg);
+	}
 
-	if (rc != OPAL_ASYNC_COMPLETION) {
+	/*
+	 * OPAL does mutual exclusion on the flash, it will return
+	 * OPAL_BUSY.
+	 * During firmware updates by the service processor OPAL may
+	 * be (temporarily) prevented from accessing the flash, in
+	 * this case OPAL will also return OPAL_BUSY.
+	 * Both cases aren't errors exactly but the flash could have
+	 * changed, userspace should be informed.
+	 */
+	if (rc != OPAL_SUCCESS && rc != OPAL_BUSY)
 		dev_err(dev, "opal_flash_async_op(op=%d) failed (rc %d)\n",
 				op, rc);
-		rc = -EIO;
-		goto out;
-	}
 
-	rc = opal_async_wait_response(token, &msg);
-	if (rc) {
-		dev_err(dev, "opal async wait failed (rc %d)\n", rc);
-		rc = -EIO;
-		goto out;
-	}
-
-	rc = opal_get_async_rc(msg);
-out_success:
-	if (rc == OPAL_SUCCESS) {
-		rc = 0;
-		if (retlen)
+	if (rc == OPAL_SUCCESS && retlen)
 			*retlen = len;
-	} else {
-		rc = -EIO;
-	}
 
+	rc = opal_error_code(rc);
 out:
 	opal_async_release_token(token);
 	return rc;
-- 
2.14.2