Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Message-ID: <61783400-4df2-47af-78a7-7acb715c3a71@gmail.com>
Date:   Tue, 12 Apr 2022 15:42:02 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.8.0
Subject: Re: [PATCH v2] mtd: rawnand: Fix return value check of
 wait_for_completion_timeout
Content-Language: en-US
To:     Miquel Raynal <miquel.raynal@bootlin.com>
Cc:     Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Pratyush Yadav <p.yadav@ti.com>,
        Paul Cercueil <paul@crapouillou.net>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Bastian Hecht <hechtb@googlemail.com>,
        Artem Bityutskiy <artem.bityutskiy@linux.intel.com>,
        Guennadi Liakhovetski <g.liakhovetski@gmx.de>,
        linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
References: <202204121253.NcZifMQi-lkp@intel.com>
 <20220412063703.8537-1-linmq006@gmail.com> <20220412090649.33bb3f8b@xps13>
From:   Miaoqian Lin <linmq006@gmail.com>
In-Reply-To: <20220412090649.33bb3f8b@xps13>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk


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