Subject: Re: [PATCH v3 4/8] DMA: Freescale: add fsl_dma_free_descriptor() to reduce code duplication

From: Hongbo Zhang <[email-masked]>
Date: Fri, 11 Apr 2014 16:14:35 +0800

On 04/10/2014 07:29 PM, Andy Shevchenko wrote:
> On Thu, 2014-04-10 at 15:10 +0800, [email-masked] wrote:
>> From: Hongbo Zhang <[email-masked]>
>>
>> There are several places where descriptors are freed using identical code.
>> This patch puts this code into a function to reduce code duplication.
>>
>> Signed-off-by: Hongbo Zhang <[email-masked]>
>> Signed-off-by: Qiang Liu <[email-masked]>
>> ---
>>   drivers/dma/fsldma.c |   30 ++++++++++++++++++------------
>>   1 file changed, 18 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c
>> index b71cc04..b5a0ffa 100644
>> --- a/drivers/dma/fsldma.c
>> +++ b/drivers/dma/fsldma.c
>> @@ -418,6 +418,19 @@ static dma_cookie_t fsl_dma_tx_submit(struct dma_async_tx_descriptor *tx)
>>   }
>>   
>>   /**
>> + * fsl_dma_free_descriptor - Free descriptor from channel's DMA pool.
>> + * @chan : Freescale DMA channel
>> + * @desc: descriptor to be freed
>> + */
>> +static void fsl_dma_free_descriptor(struct fsldma_chan *chan,
>> +		struct fsl_desc_sw *desc)
>> +{
>> +	list_del(&desc->node);
>> +	chan_dbg(chan, "LD %p free\n", desc);
>> +	dma_pool_free(chan->desc_pool, desc, desc->async_tx.phys);
>> +}
>> +
>> +/**
>>    * fsl_dma_alloc_descriptor - Allocate descriptor from channel's DMA pool.
>>    * @chan : Freescale DMA channel
>>    *
>> @@ -489,11 +502,8 @@ static void fsldma_free_desc_list(struct fsldma_chan *chan,
>>   {
>>   	struct fsl_desc_sw *desc, *_desc;
>>   
>> -	list_for_each_entry_safe(desc, _desc, list, node) {
>> -		list_del(&desc->node);
>> -		chan_dbg(chan, "LD %p free\n", desc);
>> -		dma_pool_free(chan->desc_pool, desc, desc->async_tx.phys);
>> -	}
>> +	list_for_each_entry_safe(desc, _desc, list, node)
>> +		fsl_dma_free_descriptor(chan, desc);
>>   }
>>   
>>   static void fsldma_free_desc_list_reverse(struct fsldma_chan *chan,
>> @@ -501,11 +511,8 @@ static void fsldma_free_desc_list_reverse(struct fsldma_chan *chan,
>>   {
>>   	struct fsl_desc_sw *desc, *_desc;
>>   
>> -	list_for_each_entry_safe_reverse(desc, _desc, list, node) {
>> -		list_del(&desc->node);
>> -		chan_dbg(chan, "LD %p free\n", desc);
>> -		dma_pool_free(chan->desc_pool, desc, desc->async_tx.phys);
>> -	}
>> +	list_for_each_entry_safe_reverse(desc, _desc, list, node)
>> +		fsl_dma_free_descriptor(chan, desc);
>>   }
>>   
>>   /**
>> @@ -819,8 +826,7 @@ static void fsldma_cleanup_descriptor(struct fsldma_chan *chan,
>>   	dma_run_dependencies(txd);
>>   
>>   	dma_descriptor_unmap(txd);
>> -	chan_dbg(chan, "LD %p free\n", desc);
>> -	dma_pool_free(chan->desc_pool, desc, txd->phys);
>> +	fsl_dma_free_descriptor(chan, desc);
> Here is no list_del() call since it's been called in dma_do_tasklet().
> What will be the result of double list_del() against the same node?

Not clear with your point.
This patch is only introducing a common fsl_dma_free_descriptor() to 
reduce code duplication. And later in the patch 6/8 the 
fsldma_cleanup_descriptor() is replaced by fsldma_cleanup_descriptorS().

>>   }
>>   /**