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 18:39:36 +0530
From:	Jassi Brar <jassisinghbrar@...il.com>
To:	Inderpal Singh <inderpal.singh@...aro.org>
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 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()

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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