linux-kernel - Re: [PATCH 2/3] DMA: PL330: Change allocation method to properly free DMA descriptors

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Date:	Tue, 25 Sep 2012 20:56:45 +0530
From:	Inderpal Singh <inderpal.singh@...aro.org>
To:	Jassi Brar <jassisinghbrar@...il.com>
Cc:	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	boojin.kim@...sung.com, vinod.koul@...el.com, patches@...aro.org,
	kgene.kim@...sung.com
Subject: Re: [PATCH 2/3] DMA: PL330: Change allocation method to properly free
 DMA descriptors

On 25 September 2012 18:39, Jassi Brar <jassisinghbrar@...il.com> wrote:
> On Tue, Sep 25, 2012 at 2:27 PM, Inderpal Singh
> <inderpal.singh@...aro.org> 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
>>
>> Signed-off-by: Inderpal Singh <inderpal.singh@...aro.org>
>> ---
>>  drivers/dma/pl330.c |   28 +++++++++++++++++++++-------
>>  1 file changed, 21 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
>> index 10c6b6a..04d83e6 100644
>> --- a/drivers/dma/pl330.c
>> +++ b/drivers/dma/pl330.c
>> @@ -2541,20 +2541,19 @@ 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;
>> -
>>         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);
>> +               desc = kmalloc(sizeof(*desc), flg);
>> +               if (!desc)
>> +                       break;
>> +               _init_desc(desc);
>> +               list_add_tail(&desc->node, &pdmac->desc_pool);
>>         }
>>
>>         spin_unlock_irqrestore(&pdmac->pool_lock, flags);
>>
>> -       return count;
>> +       return i;
>>  }
>>
> OK, but the kmalloc shouldn't be done with irqs disabled. Please
> protect only the list_add_tail()
>
Yes, I missed it. I will update and send it again.

Thanks,
Inder

> thanks.
>
>>  static struct dma_pl330_desc *
>> @@ -2857,6 +2856,7 @@ 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 +2978,12 @@ 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 +3000,7 @@ 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 +3022,13 @@ 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);
>> --
>> 1.7.9.5
>>
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