linux-kernel - Re: [PATCH] staging: ion: Add a default struct device for cma heap

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Message-ID: <xa1t8u9owspf.fsf@mina86.com>
Date:	Thu, 06 Aug 2015 13:40:28 +0200
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Feng Tang <feng.tang@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	John Stultz <john.stultz@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	linux-kernel@...r.kernel.org
Cc:	Feng Tang <feng.tang@...el.com>
Subject: Re: [PATCH] staging: ion: Add a default struct device for cma heap

On Thu, Aug 06 2015, Feng Tang wrote:
> When trying to use several cma heaps on our platforms,
> we met a memory issue due to that the several cma_heaps
> are sharing the same "struct device *".
>
> As in current code base, the normal cma heap creating
> process is, one platform device is created during boot,
> and it will sequentially create cma heaps (usually passing
> its own struct device * as a parameter)
>
> For the multiple cma heaps case, there will be one "struct
> cma" created for each cma heap, and this "struct cma *" is
> saved in dev->cma_area. So the single platform device can't
> meet the requirement here.
>
> So this patch add one default device for a cma heap to avoid
> sharing the same "struct device", thus fix the issue. And it
> doesn't break existing code by only using that default device
> when no "struct device *" is passed in.
>
> Also, since the cma framework has been cleaned up, this patch
> also add a platform data member to pass the "struct cma*" to
> ion_cma_heap_create().
>
> Signed-off-by: Feng Tang <feng.tang@...el.com>

>From CMA’s point of view:

Acked-by: Michal Nazarewicz <mina86@...a86.com>

> ---
>  drivers/staging/android/ion/ion.h          |    4 ++++
>  drivers/staging/android/ion/ion_cma_heap.c |   20 +++++++++++++++++---
>  2 files changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/staging/android/ion/ion.h b/drivers/staging/android/ion/ion.h
> index 443db84..e9af17e 100644
> --- a/drivers/staging/android/ion/ion.h
> +++ b/drivers/staging/android/ion/ion.h
> @@ -45,6 +45,9 @@ struct ion_buffer;
>   * @size:	size of the heap in bytes if applicable
>   * @align:	required alignment in physical memory if applicable
>   * @priv:	private info passed from the board file
> + * @priv2:	when creating CMA heap, platform device should better also
> + *		pass the "struct cma *" info, so that the cma buffer request
> + *		know where to go for the buffer
>   *
>   * Provided by the board file.
>   */
> @@ -56,6 +59,7 @@ struct ion_platform_heap {
>  	size_t size;
>  	ion_phys_addr_t align;
>  	void *priv;
> +	void *priv2;

Why are those void pointers anyway? Perhaps just make them struct device
*dev and struct cma *cma? Especially since priv2 is a bit awkward name.

>  };
>  
>  /**
> diff --git a/drivers/staging/android/ion/ion_cma_heap.c b/drivers/staging/android/ion/ion_cma_heap.c
> index f4211f1..b3e8896 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;
>  };
>  
>  #define to_cma_heap(x) container_of(x, struct ion_cma_heap, heap)
> @@ -180,9 +181,22 @@ 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;
> +
> +	/*
> +	 * data->priv for cma heap is currently supposed to point
> +	 * to a "struct device *"
> +	 */
> +	if (data->priv) {
> +		cma_heap->dev = data->priv;
> +	} else {
> +		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->priv2 contains a pointer to struct cma */
> +	dev_set_cma_area(cma_heap->dev, data->priv2);

Perhaps:

+	if (data->priv2)
+		dev_set_cma_area(cma_heap->dev, data->priv2);

> +
>  	cma_heap->heap.type = ION_HEAP_TYPE_DMA;
>  	return &cma_heap->heap;
>  }
> -- 
> 1.7.9.5
>

-- 
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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