Re: crypto: stm32 - Revert broken pm_runtime_resume_and_get changes

[Heiner Kallweit <hkallweit1@gmail.com>]

On 01.12.2021 07:30, Herbert Xu wrote:
> 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?

Looks good to me, thanks!

> 
> ---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++);
>