linux-kernel - Re: [PATCH] CMA: Don't return a valid cma for non-cma dev

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Message-ID: <xa1tio8uc7fd.fsf@mina86.com>
Date:	Wed, 05 Aug 2015 13:15:50 +0200
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Feng Tang <feng.tang@...el.com>
Cc:	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	"m.szyprowski\@samsung.com" <m.szyprowski@...sung.com>,
	"kyungmin.park\@samsung.com" <kyungmin.park@...sung.com>,
	"akpm\@linux-foundation.org" <akpm@...ux-foundation.org>,
	"iamjoonsoo.kim\@lge.com" <iamjoonsoo.kim@....com>,
	"john.stultz\@linaro.org" <john.stultz@...aro.org>
Subject: Re: [PATCH] CMA: Don't return a valid cma for non-cma dev

> On Wed, Aug 05, 2015 at 12:28:03PM +0200, Michal Nazarewicz wrote:
>> If you need several CMA areas to allocate from, create multiple struct
>> devices.

On Wed, Aug 05 2015, Feng Tang wrote:
> I've made a quick patch, which works ok on our multiple cma heap cases.

> ---
> diff --git a/drivers/staging/android/ion/ion_cma_heap.c b/drivers/staging/android/ion/ion_cma_heap.c
> index f4211f1..ee9c5d1 100644
> --- a/drivers/staging/android/ion/ion_cma_heap.c
> +++ b/drivers/staging/android/ion/ion_cma_heap.c
> @@ -29,6 +29,7 @@
>  struct ion_cma_heap {
>  	struct ion_heap heap;
>  	struct device *dev;
> +	struct device default_dma_dev;

I’m unfamiliar with ION code so cannot comment in great detail, butwhy
do you need dev and default_dma_dev fields?  Just make dev a non-pointer
and use that.

>  };
>  
>  #define to_cma_heap(x) container_of(x, struct ion_cma_heap, heap)
> @@ -180,9 +181,14 @@ struct ion_heap *ion_cma_heap_create(struct ion_platform_heap *data)
>  		return ERR_PTR(-ENOMEM);
>  
>  	cma_heap->heap.ops = &ion_cma_ops;
> -	/* get device from private heaps data, later it will be
> -	 * used to make the link with reserved CMA memory */
> -	cma_heap->dev = data->priv;
> +
> +	cma_heap->dev = &cma_heap->default_dma_dev;
> +	cma_heap->dev->coherent_dma_mask = DMA_BIT_MASK(32);
> +	cma_heap->dev->dma_mask = &dev->coherent_dma_mask;
> +
> +	/* data->priv contains a pointer to struct cma */
> +	dev_set_cma_area(cma_heap->dev, data->priv);

In the previous code, data->priv seemed to be struct device*, but in
this code it is used as struct cma*.

> +
>  	cma_heap->heap.type = ION_HEAP_TYPE_DMA;
>  	return &cma_heap->heap;
>  }

But yeah, in general, from CMA’s point of view, this looks good.

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +--<mpn@...gle.com>--<xmpp:mina86@...ber.org>--ooO--(_)--Ooo--
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