linux-kernel - Re: [PATCH v2 2/4] DMA: PL330: Change allocation method to properly free DMA descriptors

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Date:	Thu, 25 Oct 2012 16:32:23 +0530
From:	Inderpal Singh <inderpal.singh@...aro.org>
To:	Vinod Koul <vkoul@...radead.org>
Cc:	vinod.koul@...el.com, linux-samsung-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org, jassisinghbrar@...il.com,
	boojin.kim@...sung.com, patches@...aro.org, kgene.kim@...sung.com
Subject: Re: [PATCH v2 2/4] DMA: PL330: Change allocation method to properly
 free DMA descriptors

On 24 October 2012 09:40, Vinod Koul <vkoul@...radead.org> wrote:
> On Fri, 2012-10-05 at 15:47 +0530, Inderpal Singh wrote:
>> In probe, memory for multiple DMA descriptors were being allocated at once
>> and then it was being split and added into DMA pool one by one. The address
>> of this memory allocation is not being saved anywhere. To free this memory,
>> the address is required. Initially the first node of the pool will be
>> pointed by this address but as we use this pool the descs will shuffle and
>> hence we will lose the track of the address.
>>
>> This patch does following:
>>
>> 1. Allocates DMA descs one by one and then adds them to pool so that all
>>    descs can be fetched and memory freed one by one. This way runtime
>>    added descs can also be freed.
>> 2. Free DMA descs in case of error in probe and in module's remove function
> For probe, again you have cleaner code by using devm_kzalloc.
>
> On 1, if we use the devm_kzalloc then we don't need to allocate in
> chunks right?
>

Yes, if we use devm_kzalloc we wont have to allocate in chunks.
I will update this patch to use devm_kzalloc and send it again.


>>
>> Signed-off-by: Inderpal Singh <inderpal.singh@...aro.org>
>> ---
>>  drivers/dma/pl330.c |   35 +++++++++++++++++++++++++----------
>>  1 file changed, 25 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
>> index 10c6b6a..bf71ff7 100644
>> --- a/drivers/dma/pl330.c
>> +++ b/drivers/dma/pl330.c
>> @@ -2541,20 +2541,20 @@ static int add_desc(struct dma_pl330_dmac *pdmac, gfp_t flg, int count)
>>       if (!pdmac)
>>               return 0;
>>
>> -     desc = kmalloc(count * sizeof(*desc), flg);
>> -     if (!desc)
>> -             return 0;
>> +     for (i = 0; i < count; i++) {
>> +             desc = kmalloc(sizeof(*desc), flg);
>> +             if (!desc)
>> +                     break;
>> +             _init_desc(desc);
>>
>> -     spin_lock_irqsave(&pdmac->pool_lock, flags);
>> +             spin_lock_irqsave(&pdmac->pool_lock, flags);
>>
>> -     for (i = 0; i < count; i++) {
>> -             _init_desc(&desc[i]);
>> -             list_add_tail(&desc[i].node, &pdmac->desc_pool);
>> -     }
>> +             list_add_tail(&desc->node, &pdmac->desc_pool);
>>
>> -     spin_unlock_irqrestore(&pdmac->pool_lock, flags);
>> +             spin_unlock_irqrestore(&pdmac->pool_lock, flags);
>> +     }
>>
>> -     return count;
>> +     return i;
>>  }
>>
>>  static struct dma_pl330_desc *
>> @@ -2857,6 +2857,7 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id)
>>       struct dma_pl330_platdata *pdat;
>>       struct dma_pl330_dmac *pdmac;
>>       struct dma_pl330_chan *pch;
>> +     struct dma_pl330_desc *desc;
>>       struct pl330_info *pi;
>>       struct dma_device *pd;
>>       struct resource *res;
>> @@ -2978,6 +2979,12 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id)
>>  probe_err5:
>>       kfree(pdmac->peripherals);
>>  probe_err4:
>> +     while (!list_empty(&pdmac->desc_pool)) {
>> +             desc = list_entry(pdmac->desc_pool.next,
>> +                             struct dma_pl330_desc, node);
>> +             list_del(&desc->node);
>> +             kfree(desc);
>> +     }
>>       pl330_del(pi);
>>  probe_err3:
>>       free_irq(irq, pi);
>> @@ -2994,6 +3001,7 @@ static int __devexit pl330_remove(struct amba_device *adev)
>>  {
>>       struct dma_pl330_dmac *pdmac = amba_get_drvdata(adev);
>>       struct dma_pl330_chan *pch, *_p;
>> +     struct dma_pl330_desc *desc;
>>       struct pl330_info *pi;
>>       struct resource *res;
>>       int irq;
>> @@ -3015,6 +3023,13 @@ static int __devexit pl330_remove(struct amba_device *adev)
>>               pl330_free_chan_resources(&pch->chan);
>>       }
>>
>> +     while (!list_empty(&pdmac->desc_pool)) {
>> +             desc = list_entry(pdmac->desc_pool.next,
>> +                             struct dma_pl330_desc, node);
>> +             list_del(&desc->node);
>> +             kfree(desc);
>> +     }
>> +
>>       pi = &pdmac->pif;
>>
>>       pl330_del(pi);
>
>
> --
> Vinod Koul
> Intel Corp.
>
Regards,
Inder
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