[PATCH] mtd: rawnand: Fix return value check of wait_for_completion_timeout

[PATCH] mtd: rawnand: Fix return value check of wait_for_completion_timeout

[Miaoqian Lin]

wait_for_completion_timeout() returns unsigned long not int.
It returns 0 if timed out, and positive if completed.
The check for <= 0 is ambiguous and should be == 0 here
indicating timeout which is the only error case.

Fixes: 83738d87e3a0 ("mtd: sh_flctl: Add DMA capabilty")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
---
 drivers/mtd/nand/raw/sh_flctl.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/raw/sh_flctl.c b/drivers/mtd/nand/raw/sh_flctl.c
index b85b9c6fcc42..4f326a2dd170 100644
--- a/drivers/mtd/nand/raw/sh_flctl.c
+++ b/drivers/mtd/nand/raw/sh_flctl.c
@@ -385,6 +385,7 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
 	dma_cookie_t cookie;
 	uint32_t reg;
 	int ret;
+	unsigned long time_left;
 
 	if (dir == DMA_FROM_DEVICE) {
 		chan = flctl->chan_fifo0_rx;
@@ -425,13 +426,14 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
 		goto out;
 	}
 
-	ret =
+	time_left =
 	wait_for_completion_timeout(&flctl->dma_complete,
 				msecs_to_jiffies(3000));
 
-	if (ret <= 0) {
+	if (time_left == 0) {
 		dmaengine_terminate_all(chan);
 		dev_err(&flctl->pdev->dev, "wait_for_completion_timeout\n");
+		ret = -ETIMEDOUT;
 	}
 
 out:
-- 
2.17.1

Re: [PATCH] mtd: rawnand: Fix return value check of wait_for_completion_timeout

[kernel test robot]

Hi Miaoqian,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on mtd/nand/next]
[also build test WARNING on linus/master linux/master v5.18-rc2 next-20220411]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/intel-lab-lkp/linux/commits/Miaoqian-Lin/mtd-rawnand-Fix-return-value-check-of-wait_for_completion_timeout/20220412-101006
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next
config: hexagon-randconfig-r045-20220411 (https://download.01.org/0day-ci/archive/20220412/202204121253.NcZifMQi-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project fe2478d44e4f7f191c43fef629ac7a23d0251e72)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/3de25b46a3f73a3e0031e5186eb4e2afa9098b46
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Miaoqian-Lin/mtd-rawnand-Fix-return-value-check-of-wait_for_completion_timeout/20220412-101006
        git checkout 3de25b46a3f73a3e0031e5186eb4e2afa9098b46
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash drivers/mtd/nand/raw/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> drivers/mtd/nand/raw/sh_flctl.c:433:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
           if (time_left == 0) {
               ^~~~~~~~~~~~~~
   drivers/mtd/nand/raw/sh_flctl.c:447:9: note: uninitialized use occurs here
           return ret;
                  ^~~
   drivers/mtd/nand/raw/sh_flctl.c:433:2: note: remove the 'if' if its condition is always true
           if (time_left == 0) {
           ^~~~~~~~~~~~~~~~~~~~
   drivers/mtd/nand/raw/sh_flctl.c:387:9: note: initialize the variable 'ret' to silence this warning
           int ret;
                  ^
                   = 0
   1 warning generated.


vim +433 drivers/mtd/nand/raw/sh_flctl.c

   377	
   378	static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
   379						int len, enum dma_data_direction dir)
   380	{
   381		struct dma_async_tx_descriptor *desc = NULL;
   382		struct dma_chan *chan;
   383		enum dma_transfer_direction tr_dir;
   384		dma_addr_t dma_addr;
   385		dma_cookie_t cookie;
   386		uint32_t reg;
   387		int ret;
   388		unsigned long time_left;
   389	
   390		if (dir == DMA_FROM_DEVICE) {
   391			chan = flctl->chan_fifo0_rx;
   392			tr_dir = DMA_DEV_TO_MEM;
   393		} else {
   394			chan = flctl->chan_fifo0_tx;
   395			tr_dir = DMA_MEM_TO_DEV;
   396		}
   397	
   398		dma_addr = dma_map_single(chan->device->dev, buf, len, dir);
   399	
   400		if (!dma_mapping_error(chan->device->dev, dma_addr))
   401			desc = dmaengine_prep_slave_single(chan, dma_addr, len,
   402				tr_dir, DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
   403	
   404		if (desc) {
   405			reg = readl(FLINTDMACR(flctl));
   406			reg |= DREQ0EN;
   407			writel(reg, FLINTDMACR(flctl));
   408	
   409			desc->callback = flctl_dma_complete;
   410			desc->callback_param = flctl;
   411			cookie = dmaengine_submit(desc);
   412			if (dma_submit_error(cookie)) {
   413				ret = dma_submit_error(cookie);
   414				dev_warn(&flctl->pdev->dev,
   415					 "DMA submit failed, falling back to PIO\n");
   416				goto out;
   417			}
   418	
   419			dma_async_issue_pending(chan);
   420		} else {
   421			/* DMA failed, fall back to PIO */
   422			flctl_release_dma(flctl);
   423			dev_warn(&flctl->pdev->dev,
   424				 "DMA failed, falling back to PIO\n");
   425			ret = -EIO;
   426			goto out;
   427		}
   428	
   429		time_left =
   430		wait_for_completion_timeout(&flctl->dma_complete,
   431					msecs_to_jiffies(3000));
   432	
 > 433		if (time_left == 0) {
   434			dmaengine_terminate_all(chan);
   435			dev_err(&flctl->pdev->dev, "wait_for_completion_timeout\n");
   436			ret = -ETIMEDOUT;
   437		}
   438	
   439	out:
   440		reg = readl(FLINTDMACR(flctl));
   441		reg &= ~DREQ0EN;
   442		writel(reg, FLINTDMACR(flctl));
   443	
   444		dma_unmap_single(chan->device->dev, dma_addr, len, dir);
   445	
   446		/* ret > 0 is success */
   447		return ret;
   448	}
   449	

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

[PATCH v2] mtd: rawnand: Fix return value check of wait_for_completion_timeout

[Miaoqian Lin]

wait_for_completion_timeout() returns unsigned long not int.
It returns 0 if timed out, and positive if completed.
The check for <= 0 is ambiguous and should be == 0 here
indicating timeout which is the only error case.

Fixes: 83738d87e3a0 ("mtd: sh_flctl: Add DMA capabilty")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
---
change in v2:
- initialize ret to 1.
---
 drivers/mtd/nand/raw/sh_flctl.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/raw/sh_flctl.c b/drivers/mtd/nand/raw/sh_flctl.c
index b85b9c6fcc42..2373251f585b 100644
--- a/drivers/mtd/nand/raw/sh_flctl.c
+++ b/drivers/mtd/nand/raw/sh_flctl.c
@@ -384,7 +384,8 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
 	dma_addr_t dma_addr;
 	dma_cookie_t cookie;
 	uint32_t reg;
-	int ret;
+	int ret = 1;
+	unsigned long time_left;
 
 	if (dir == DMA_FROM_DEVICE) {
 		chan = flctl->chan_fifo0_rx;
@@ -425,13 +426,14 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
 		goto out;
 	}
 
-	ret =
+	time_left =
 	wait_for_completion_timeout(&flctl->dma_complete,
 				msecs_to_jiffies(3000));
 
-	if (ret <= 0) {
+	if (time_left == 0) {
 		dmaengine_terminate_all(chan);
 		dev_err(&flctl->pdev->dev, "wait_for_completion_timeout\n");
+		ret = -ETIMEDOUT;
 	}
 
 out:
-- 
2.17.1

Re: [PATCH v2] mtd: rawnand: Fix return value check of wait_for_completion_timeout

[Miquel Raynal]

Hi Miaoqian,

linmq006@gmail.com wrote on Tue, 12 Apr 2022 06:36:52 +0000:

> wait_for_completion_timeout() returns unsigned long not int.
> It returns 0 if timed out, and positive if completed.
> The check for <= 0 is ambiguous and should be == 0 here
> indicating timeout which is the only error case.
> 
> Fixes: 83738d87e3a0 ("mtd: sh_flctl: Add DMA capabilty")
> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
> ---
> change in v2:
> - initialize ret to 1.
> ---
>  drivers/mtd/nand/raw/sh_flctl.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/sh_flctl.c b/drivers/mtd/nand/raw/sh_flctl.c
> index b85b9c6fcc42..2373251f585b 100644
> --- a/drivers/mtd/nand/raw/sh_flctl.c
> +++ b/drivers/mtd/nand/raw/sh_flctl.c
> @@ -384,7 +384,8 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
>  	dma_addr_t dma_addr;
>  	dma_cookie_t cookie;
>  	uint32_t reg;
> -	int ret;
> +	int ret = 1;

Does not look right. I know this function returns > 0 on positive
outcomes but this does not make any sense in the first place.

This function is static and only called twice, please turn it into
something like:

if (dma_fifo_transfer())
	error
else
	ok

> +	unsigned long time_left;
>  
>  	if (dir == DMA_FROM_DEVICE) {
>  		chan = flctl->chan_fifo0_rx;
> @@ -425,13 +426,14 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
>  		goto out;
>  	}
>  
> -	ret =
> +	time_left =
>  	wait_for_completion_timeout(&flctl->dma_complete,
>  				msecs_to_jiffies(3000));
>  
> -	if (ret <= 0) {
> +	if (time_left == 0) {
>  		dmaengine_terminate_all(chan);
>  		dev_err(&flctl->pdev->dev, "wait_for_completion_timeout\n");
> +		ret = -ETIMEDOUT;
>  	}
>  
>  out:


Thanks,
Miquèl

Re: [PATCH v2] mtd: rawnand: Fix return value check of wait_for_completion_timeout

[Miaoqian Lin]

Hi Miquel,

Thanks for your reply.

On 2022/4/12 15:06, Miquel Raynal wrote:
> Hi Miaoqian,
>
> linmq006@gmail.com wrote on Tue, 12 Apr 2022 06:36:52 +0000:
>
>> wait_for_completion_timeout() returns unsigned long not int.
>> It returns 0 if timed out, and positive if completed.
>> The check for <= 0 is ambiguous and should be == 0 here
>> indicating timeout which is the only error case.
>>
>> Fixes: 83738d87e3a0 ("mtd: sh_flctl: Add DMA capabilty")
>> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
>> ---
>> change in v2:
>> - initialize ret to 1.
>> ---
>>  drivers/mtd/nand/raw/sh_flctl.c | 8 +++++---
>>  1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/raw/sh_flctl.c b/drivers/mtd/nand/raw/sh_flctl.c
>> index b85b9c6fcc42..2373251f585b 100644
>> --- a/drivers/mtd/nand/raw/sh_flctl.c
>> +++ b/drivers/mtd/nand/raw/sh_flctl.c
>> @@ -384,7 +384,8 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
>>  	dma_addr_t dma_addr;
>>  	dma_cookie_t cookie;
>>  	uint32_t reg;
>> -	int ret;
>> +	int ret = 1;
> Does not look right. I know this function returns > 0 on positive
> outcomes but this does not make any sense in the first place.

Yes, I made a mistake, Now I realize that in v2, it will return 1 in error path

when DMA submit failed.

And for patch v1, it will return 0  if calls wait_for_completion_timeout succeeds.

> This function is static and only called twice, please turn it into
> something like:
>
> if (dma_fifo_transfer())
> 	error
> else
> 	ok

So I want to keep ret>0 means success.

Or could I set ret > 0 after in wait_for_completion_timeout() success path?

like:

    if(time_left == 0)

            ret = -ETIMEDOUT;

    else

            ret = 1;

What do you think?


Thanks,

>> +	unsigned long time_left;
>>  
>>  	if (dir == DMA_FROM_DEVICE) {
>>  		chan = flctl->chan_fifo0_rx;
>> @@ -425,13 +426,14 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
>>  		goto out;
>>  	}
>>  
>> -	ret =
>> +	time_left =
>>  	wait_for_completion_timeout(&flctl->dma_complete,
>>  				msecs_to_jiffies(3000));
>>  
>> -	if (ret <= 0) {
>> +	if (time_left == 0) {
>>  		dmaengine_terminate_all(chan);
>>  		dev_err(&flctl->pdev->dev, "wait_for_completion_timeout\n");
>> +		ret = -ETIMEDOUT;
>>  	}
>>  
>>  out:
>
> Thanks,
> Miquèl

Re: [PATCH v2] mtd: rawnand: Fix return value check of wait_for_completion_timeout

[Miquel Raynal]

Hi Miaoqian,

linmq006@gmail.com wrote on Tue, 12 Apr 2022 15:42:02 +0800:

> Hi Miquel,
> 
> Thanks for your reply.
> 
> On 2022/4/12 15:06, Miquel Raynal wrote:
> > Hi Miaoqian,
> >
> > linmq006@gmail.com wrote on Tue, 12 Apr 2022 06:36:52 +0000:
> >  
> >> wait_for_completion_timeout() returns unsigned long not int.
> >> It returns 0 if timed out, and positive if completed.
> >> The check for <= 0 is ambiguous and should be == 0 here
> >> indicating timeout which is the only error case.
> >>
> >> Fixes: 83738d87e3a0 ("mtd: sh_flctl: Add DMA capabilty")
> >> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
> >> ---
> >> change in v2:
> >> - initialize ret to 1.
> >> ---
> >>  drivers/mtd/nand/raw/sh_flctl.c | 8 +++++---
> >>  1 file changed, 5 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/mtd/nand/raw/sh_flctl.c b/drivers/mtd/nand/raw/sh_flctl.c
> >> index b85b9c6fcc42..2373251f585b 100644
> >> --- a/drivers/mtd/nand/raw/sh_flctl.c
> >> +++ b/drivers/mtd/nand/raw/sh_flctl.c
> >> @@ -384,7 +384,8 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
> >>  	dma_addr_t dma_addr;
> >>  	dma_cookie_t cookie;
> >>  	uint32_t reg;
> >> -	int ret;
> >> +	int ret = 1;  
> > Does not look right. I know this function returns > 0 on positive
> > outcomes but this does not make any sense in the first place.  
> 
> Yes, I made a mistake, Now I realize that in v2, it will return 1 in error path
> 
> when DMA submit failed.

Not 1, but a proper error code please (-ETIMEDOUT, -EINVAL, whatever)

> 
> And for patch v1, it will return 0  if calls wait_for_completion_timeout succeeds.
> 
> > This function is static and only called twice, please turn it into
> > something like:
> >
> > if (dma_fifo_transfer())
> > 	error
> > else
> > 	ok  
> 
> So I want to keep ret>0 means success.
> 
> Or could I set ret > 0 after in wait_for_completion_timeout() success path?
> 
> like:
> 
>     if(time_left == 0)
> 
>             ret = -ETIMEDOUT;
> 
>     else
> 
>             ret = 1;

You can initialize ret to zero at to top. So that anything != 0 is an
error (like a lot of functions in the kernel). And use:

	if (dma_fifo_transfer())
		error();

> 
> What do you think?
> 
> 
> Thanks,
> 
> >> +	unsigned long time_left;
> >>  
> >>  	if (dir == DMA_FROM_DEVICE) {
> >>  		chan = flctl->chan_fifo0_rx;
> >> @@ -425,13 +426,14 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
> >>  		goto out;
> >>  	}
> >>  
> >> -	ret =
> >> +	time_left =
> >>  	wait_for_completion_timeout(&flctl->dma_complete,
> >>  				msecs_to_jiffies(3000));
> >>  
> >> -	if (ret <= 0) {
> >> +	if (time_left == 0) {
> >>  		dmaengine_terminate_all(chan);
> >>  		dev_err(&flctl->pdev->dev, "wait_for_completion_timeout\n");
> >> +		ret = -ETIMEDOUT;
> >>  	}
> >>  
> >>  out:  
> >
> > Thanks,
> > Miquèl  


Thanks,
Miquèl

Re: [PATCH v2] mtd: rawnand: Fix return value check of wait_for_completion_timeout

[Miaoqian Lin]

Hi Miquel,

On 2022/4/12 15:48, Miquel Raynal wrote:
>
>>> Hi Miaoqian,
>>>
>>> linmq006@gmail.com wrote on Tue, 12 Apr 2022 06:36:52 +0000:
>>>  
>>>> wait_for_completion_timeout() returns unsigned long not int.
>>>> It returns 0 if timed out, and positive if completed.
>>>> The check for <= 0 is ambiguous and should be == 0 here
>>>> indicating timeout which is the only error case.
>>>>
>>>> Fixes: 83738d87e3a0 ("mtd: sh_flctl: Add DMA capabilty")
>>>> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
>>>> ---
>>>> change in v2:
>>>> - initialize ret to 1.
>>>> ---
>>>>  drivers/mtd/nand/raw/sh_flctl.c | 8 +++++---
>>>>  1 file changed, 5 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/mtd/nand/raw/sh_flctl.c b/drivers/mtd/nand/raw/sh_flctl.c
>>>> index b85b9c6fcc42..2373251f585b 100644
>>>> --- a/drivers/mtd/nand/raw/sh_flctl.c
>>>> +++ b/drivers/mtd/nand/raw/sh_flctl.c
>>>> @@ -384,7 +384,8 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
>>>>  	dma_addr_t dma_addr;
>>>>  	dma_cookie_t cookie;
>>>>  	uint32_t reg;
>>>> -	int ret;
>>>> +	int ret = 1;  
>>> Does not look right. I know this function returns > 0 on positive
>>> outcomes but this does not make any sense in the first place.  
>> Yes, I made a mistake, Now I realize that in v2, it will return 1 in error path
>>
>> when DMA submit failed.
> Not 1, but a proper error code please (-ETIMEDOUT, -EINVAL, whatever)
>
>> And for patch v1, it will return 0  if calls wait_for_completion_timeout succeeds.
>>
>>> This function is static and only called twice, please turn it into
>>> something like:
>>>
>>> if (dma_fifo_transfer())
>>> 	error
>>> else
>>> 	ok  
>> So I want to keep ret>0 means success.
>>
>> Or could I set ret > 0 after in wait_for_completion_timeout() success path?
>>
>> like:
>>
>>     if(time_left == 0)
>>
>>             ret = -ETIMEDOUT;
>>
>>     else
>>
>>             ret = 1;
> You can initialize ret to zero at to top. So that anything != 0 is an
> error (like a lot of functions in the kernel). 

Thanks for your advice, I will do this.
> And use:
>
> 	if (dma_fifo_transfer())
> 		error();
I think keeping the original condition structure is better,
something like:

if (dma_fifo_transfer()==0)
	succeed();

In this way, only minor changes is needed——only need to update the symbol in condition.
Otherwise It needs to restructure the code and be more complicated.


Thanks,

>> What do you think?
>>
>>
>> Thanks,
>>
>>>> +	unsigned long time_left;
>>>>  
>>>>  	if (dir == DMA_FROM_DEVICE) {
>>>>  		chan = flctl->chan_fifo0_rx;
>>>> @@ -425,13 +426,14 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
>>>>  		goto out;
>>>>  	}
>>>>  
>>>> -	ret =
>>>> +	time_left =
>>>>  	wait_for_completion_timeout(&flctl->dma_complete,
>>>>  				msecs_to_jiffies(3000));
>>>>  
>>>> -	if (ret <= 0) {
>>>> +	if (time_left == 0) {
>>>>  		dmaengine_terminate_all(chan);
>>>>  		dev_err(&flctl->pdev->dev, "wait_for_completion_timeout\n");
>>>> +		ret = -ETIMEDOUT;
>>>>  	}
>>>>  
>>>>  out:  
>>> Thanks,
>>> Miquèl  
>
> Thanks,
> Miquèl

Re: [PATCH v2] mtd: rawnand: Fix return value check of wait_for_completion_timeout

[Miquel Raynal]

Hi Miaoqian,

linmq006@gmail.com wrote on Tue, 12 Apr 2022 16:23:24 +0800:

> Hi Miquel,
> 
> On 2022/4/12 15:48, Miquel Raynal wrote:
> >  
> >>> Hi Miaoqian,
> >>>
> >>> linmq006@gmail.com wrote on Tue, 12 Apr 2022 06:36:52 +0000:
> >>>    
> >>>> wait_for_completion_timeout() returns unsigned long not int.
> >>>> It returns 0 if timed out, and positive if completed.
> >>>> The check for <= 0 is ambiguous and should be == 0 here
> >>>> indicating timeout which is the only error case.
> >>>>
> >>>> Fixes: 83738d87e3a0 ("mtd: sh_flctl: Add DMA capabilty")
> >>>> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
> >>>> ---
> >>>> change in v2:
> >>>> - initialize ret to 1.
> >>>> ---
> >>>>  drivers/mtd/nand/raw/sh_flctl.c | 8 +++++---
> >>>>  1 file changed, 5 insertions(+), 3 deletions(-)
> >>>>
> >>>> diff --git a/drivers/mtd/nand/raw/sh_flctl.c b/drivers/mtd/nand/raw/sh_flctl.c
> >>>> index b85b9c6fcc42..2373251f585b 100644
> >>>> --- a/drivers/mtd/nand/raw/sh_flctl.c
> >>>> +++ b/drivers/mtd/nand/raw/sh_flctl.c
> >>>> @@ -384,7 +384,8 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
> >>>>  	dma_addr_t dma_addr;
> >>>>  	dma_cookie_t cookie;
> >>>>  	uint32_t reg;
> >>>> -	int ret;
> >>>> +	int ret = 1;    
> >>> Does not look right. I know this function returns > 0 on positive
> >>> outcomes but this does not make any sense in the first place.    
> >> Yes, I made a mistake, Now I realize that in v2, it will return 1 in error path
> >>
> >> when DMA submit failed.  
> > Not 1, but a proper error code please (-ETIMEDOUT, -EINVAL, whatever)
> >  
> >> And for patch v1, it will return 0  if calls wait_for_completion_timeout succeeds.
> >>  
> >>> This function is static and only called twice, please turn it into
> >>> something like:
> >>>
> >>> if (dma_fifo_transfer())
> >>> 	error
> >>> else
> >>> 	ok    
> >> So I want to keep ret>0 means success.
> >>
> >> Or could I set ret > 0 after in wait_for_completion_timeout() success path?
> >>
> >> like:
> >>
> >>     if(time_left == 0)
> >>
> >>             ret = -ETIMEDOUT;
> >>
> >>     else
> >>
> >>             ret = 1;  
> > You can initialize ret to zero at to top. So that anything != 0 is an
> > error (like a lot of functions in the kernel).   
> 
> Thanks for your advice, I will do this.
> > And use:
> >
> > 	if (dma_fifo_transfer())
> > 		error();  
> I think keeping the original condition structure is better,
> something like:
> 
> if (dma_fifo_transfer()==0)

  if (cond && cond && !dma_fifo_transfer())

> 	succeed();
> 
> In this way, only minor changes is needed——only need to update the symbol in condition.
> Otherwise It needs to restructure the code and be more complicated.
> 
> 
> Thanks,
> 
> >> What do you think?
> >>
> >>
> >> Thanks,
> >>  
> >>>> +	unsigned long time_left;
> >>>>  
> >>>>  	if (dir == DMA_FROM_DEVICE) {
> >>>>  		chan = flctl->chan_fifo0_rx;
> >>>> @@ -425,13 +426,14 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
> >>>>  		goto out;
> >>>>  	}
> >>>>  
> >>>> -	ret =
> >>>> +	time_left =
> >>>>  	wait_for_completion_timeout(&flctl->dma_complete,
> >>>>  				msecs_to_jiffies(3000));
> >>>>  
> >>>> -	if (ret <= 0) {
> >>>> +	if (time_left == 0) {
> >>>>  		dmaengine_terminate_all(chan);
> >>>>  		dev_err(&flctl->pdev->dev, "wait_for_completion_timeout\n");
> >>>> +		ret = -ETIMEDOUT;
> >>>>  	}
> >>>>  
> >>>>  out:    
> >>> Thanks,
> >>> Miquèl    
> >
> > Thanks,
> > Miquèl  


Thanks,
Miquèl

[PATCH v3] mtd: rawnand: Fix return value check of wait_for_completion_timeout

[Miaoqian Lin]

wait_for_completion_timeout() returns unsigned long not int.
It returns 0 if timed out, and positive if completed.
The check for <= 0 is ambiguous and should be == 0 here
indicating timeout which is the only error case.

Fixes: 83738d87e3a0 ("mtd: sh_flctl: Add DMA capabilty")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
---
change in v2:
- initialize ret to 1.
---
changes in v3:
- initialize ret to 0, now ret==0 means success.
- update condition check in caller.
---
 drivers/mtd/nand/raw/sh_flctl.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/nand/raw/sh_flctl.c b/drivers/mtd/nand/raw/sh_flctl.c
index b85b9c6fcc42..a278829469d6 100644
--- a/drivers/mtd/nand/raw/sh_flctl.c
+++ b/drivers/mtd/nand/raw/sh_flctl.c
@@ -384,7 +384,8 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
 	dma_addr_t dma_addr;
 	dma_cookie_t cookie;
 	uint32_t reg;
-	int ret;
+	int ret = 0;
+	unsigned long time_left;
 
 	if (dir == DMA_FROM_DEVICE) {
 		chan = flctl->chan_fifo0_rx;
@@ -425,13 +426,14 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
 		goto out;
 	}
 
-	ret =
+	time_left =
 	wait_for_completion_timeout(&flctl->dma_complete,
 				msecs_to_jiffies(3000));
 
-	if (ret <= 0) {
+	if (time_left == 0) {
 		dmaengine_terminate_all(chan);
 		dev_err(&flctl->pdev->dev, "wait_for_completion_timeout\n");
+		ret = -ETIMEDOUT;
 	}
 
 out:
@@ -441,7 +443,7 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl *flctl, unsigned long *buf,
 
 	dma_unmap_single(chan->device->dev, dma_addr, len, dir);
 
-	/* ret > 0 is success */
+	/* ret == 0 is success */
 	return ret;
 }
 
@@ -465,7 +467,7 @@ static void read_fiforeg(struct sh_flctl *flctl, int rlen, int offset)
 
 	/* initiate DMA transfer */
 	if (flctl->chan_fifo0_rx && rlen >= 32 &&
-		flctl_dma_fifo0_transfer(flctl, buf, rlen, DMA_FROM_DEVICE) > 0)
+		!flctl_dma_fifo0_transfer(flctl, buf, rlen, DMA_FROM_DEVICE))
 			goto convert;	/* DMA success */
 
 	/* do polling transfer */
@@ -524,7 +526,7 @@ static void write_ec_fiforeg(struct sh_flctl *flctl, int rlen,
 
 	/* initiate DMA transfer */
 	if (flctl->chan_fifo0_tx && rlen >= 32 &&
-		flctl_dma_fifo0_transfer(flctl, buf, rlen, DMA_TO_DEVICE) > 0)
+		!flctl_dma_fifo0_transfer(flctl, buf, rlen, DMA_TO_DEVICE))
 			return;	/* DMA success */
 
 	/* do polling transfer */
-- 
2.17.1

Re: [PATCH v3] mtd: rawnand: Fix return value check of wait_for_completion_timeout

[Miquel Raynal]

On Tue, 2022-04-12 at 08:34:31 UTC, Miaoqian Lin wrote:
> wait_for_completion_timeout() returns unsigned long not int.
> It returns 0 if timed out, and positive if completed.
> The check for <= 0 is ambiguous and should be == 0 here
> indicating timeout which is the only error case.
> 
> Fixes: 83738d87e3a0 ("mtd: sh_flctl: Add DMA capabilty")
> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/fixes, thanks.

Miquel