crypto: stm32 - Revert broken pm_runtime_resume_and_get changes

[Herbert Xu <herbert@gondor.apana.org.au>]

On Sat, Nov 27, 2021 at 02:39:52PM +0100, Heiner Kallweit wrote:
> When discussing whether pm_runtime_resume_and_get() should be annotated as
> __must_check, I became aware of RPM usage in crypto/stm32.
> 
> Following two patches replace usage of pm_runtime_get_sync() with
> pm_runtime_resume_and_get() w/o checking the return code.
> 
> 747bf30fd944 ("crypto: stm32/cryp - Fix PM reference leak on stm32-cryp.c")
> 1cb3ad701970 ("crypto: stm32/hash - Fix PM reference leak on stm32-hash.c")
> 
> This results in RPM usage like the following in stm32_hash_export():
> 
> pm_runtime_resume_and_get(hdev->dev);
> ...
> pm_runtime_mark_last_busy(hdev->dev);
> pm_runtime_put_autosuspend(hdev->dev);
> 
> This is broken. After pm_runtime_resume_and_get() the usage count may be
> incremented or not. If not, then the call to pm_runtime_put_autosuspend()
> results in exactly the imbalance that the patch claims to fix.
> 
> Therefore I think both patches should be reverted, or the return code
> of pm_runtime_resume_and_get() has to be checked and properly handled
> in the driver logic.

I agree.  But we can't revert them completely because it does
fix some genuine issues with the ones where we do check the error
code.  What about this patch?

---8<---
We should not call pm_runtime_resume_and_get where the reference
count is expected to be incremented unconditionally.  This patch
reverts these calls to the original unconditional get_sync call.

Reported-by: Heiner Kallweit <hkallweit1@gmail.com>
Fixes: 747bf30fd944 ("crypto: stm32/cryp - Fix PM reference leak...")
Fixes: 1cb3ad701970 ("crypto: stm32/hash - Fix PM reference leak...")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/crypto/stm32/stm32-cryp.c b/drivers/crypto/stm32/stm32-cryp.c
index 7389a0536ff0..05087831e199 100644
--- a/drivers/crypto/stm32/stm32-cryp.c
+++ b/drivers/crypto/stm32/stm32-cryp.c
@@ -542,7 +542,7 @@ static int stm32_cryp_hw_init(struct stm32_cryp *cryp)
 	int ret;
 	u32 cfg, hw_mode;
 
-	pm_runtime_resume_and_get(cryp->dev);
+	pm_runtime_get_sync(cryp->dev);
 
 	/* Disable interrupt */
 	stm32_cryp_write(cryp, CRYP_IMSCR, 0);
diff --git a/drivers/crypto/stm32/stm32-hash.c b/drivers/crypto/stm32/stm32-hash.c
index 389de9e3302d..d33006d43f76 100644
--- a/drivers/crypto/stm32/stm32-hash.c
+++ b/drivers/crypto/stm32/stm32-hash.c
@@ -813,7 +813,7 @@ static void stm32_hash_finish_req(struct ahash_request *req, int err)
 static int stm32_hash_hw_init(struct stm32_hash_dev *hdev,
 			      struct stm32_hash_request_ctx *rctx)
 {
-	pm_runtime_resume_and_get(hdev->dev);
+	pm_runtime_get_sync(hdev->dev);
 
 	if (!(HASH_FLAGS_INIT & hdev->flags)) {
 		stm32_hash_write(hdev, HASH_CR, HASH_CR_INIT);
@@ -962,7 +962,7 @@ static int stm32_hash_export(struct ahash_request *req, void *out)
 	u32 *preg;
 	unsigned int i;
 
-	pm_runtime_resume_and_get(hdev->dev);
+	pm_runtime_get_sync(hdev->dev);
 
 	while ((stm32_hash_read(hdev, HASH_SR) & HASH_SR_BUSY))
 		cpu_relax();
@@ -1000,7 +1000,7 @@ static int stm32_hash_import(struct ahash_request *req, const void *in)
 
 	preg = rctx->hw_context;
 
-	pm_runtime_resume_and_get(hdev->dev);
+	pm_runtime_get_sync(hdev->dev);
 
 	stm32_hash_write(hdev, HASH_IMR, *preg++);
 	stm32_hash_write(hdev, HASH_STR, *preg++);
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt