[PATCH 1/2] mtd: powernv_flash: Use WARN_ON_ONCE() rather than BUG_ON()

[PATCH 1/2] mtd: powernv_flash: Use WARN_ON_ONCE() rather than BUG_ON()

[Cyril Bur]

BUG_ON() should be reserved in situations where we can not longer
guarantee the integrity of the system. In the case where
powernv_flash_async_op() receives an impossible op, we can still
guarantee the integrity of the system.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
---
I think patches to powernv_flash have gone through MPE in the past -
is this still correct?

 drivers/mtd/devices/powernv_flash.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/devices/powernv_flash.c b/drivers/mtd/devices/powernv_flash.c
index f5396f26ddb4..a9a20c00687c 100644
--- a/drivers/mtd/devices/powernv_flash.c
+++ b/drivers/mtd/devices/powernv_flash.c
@@ -78,7 +78,8 @@ static int powernv_flash_async_op(struct mtd_info *mtd, enum flash_op op,
 		rc = opal_flash_erase(info->id, offset, len, token);
 		break;
 	default:
-		BUG_ON(1);
+		WARN_ON_ONCE(1);
+		return -EIO;
 	}
 
 	if (rc != OPAL_ASYNC_COMPLETION) {
-- 
2.13.0

[PATCH 2/2] mtd: powernv_flash: Lock around concurrent access to OPAL

[Cyril Bur]

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>
---
This is to address https://github.com/open-power/skiboot/issues/80


 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);
 
 	/*
-- 
2.13.0

Re: [PATCH 2/2] mtd: powernv_flash: Lock around concurrent access to OPAL

[Stewart Smith]

Cyril Bur <cyrilbur@gmail.com> writes:
> 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>
> ---
> This is to address https://github.com/open-power/skiboot/issues/80

part of me wants to say "let's only take the lock if we ever get back
OPAL_BUSY" or something like that (have a DT property to say the flash
supports concurrent ops?)

Although the other part of me says "you're overthinking this, get back
to the work you're meant to be doing" :)

-- 
Stewart Smith
OPAL Architect, IBM.