linux-kernel - Re: [RFC][PATCH 3/4] dma-buf: cma_heap: Extend logic to export CMA regions tagged with "linux,cma-heap"

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Date:   Fri, 1 May 2020 11:21:43 +0100
From:   Brian Starkey <brian.starkey@....com>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        "Andrew F. Davis" <afd@...com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Pratik Patel <pratikp@...eaurora.org>,
        Laura Abbott <labbott@...hat.com>,
        Chenbo Feng <fengc@...gle.com>,
        Alistair Strachan <astrachan@...gle.com>,
        Sandeep Patil <sspatil@...gle.com>,
        Hridya Valsaraju <hridya@...gle.com>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-mm@...ck.org, nd@....com
Subject: Re: [RFC][PATCH 3/4] dma-buf: cma_heap: Extend logic to export CMA
 regions tagged with "linux,cma-heap"

Hi John,

On Fri, May 01, 2020 at 07:39:48AM +0000, John Stultz wrote:
> This patch reworks the cma_heap initialization so that
> we expose both the default CMA region and any CMA regions
> tagged with "linux,cma-heap" in the device-tree.
> 
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Sumit Semwal <sumit.semwal@...aro.org>
> Cc: "Andrew F. Davis" <afd@...com>
> Cc: Benjamin Gaignard <benjamin.gaignard@...aro.org>
> Cc: Liam Mark <lmark@...eaurora.org>
> Cc: Pratik Patel <pratikp@...eaurora.org>
> Cc: Laura Abbott <labbott@...hat.com>
> Cc: Brian Starkey <Brian.Starkey@....com>
> Cc: Chenbo Feng <fengc@...gle.com>
> Cc: Alistair Strachan <astrachan@...gle.com>
> Cc: Sandeep Patil <sspatil@...gle.com>
> Cc: Hridya Valsaraju <hridya@...gle.com>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Marek Szyprowski <m.szyprowski@...sung.com>
> Cc: Robin Murphy <robin.murphy@....com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: devicetree@...r.kernel.org
> Cc: dri-devel@...ts.freedesktop.org
> Cc: linux-mm@...ck.org
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
>  drivers/dma-buf/heaps/cma_heap.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
> index 626cf7fd033a..dd154e2db101 100644
> --- a/drivers/dma-buf/heaps/cma_heap.c
> +++ b/drivers/dma-buf/heaps/cma_heap.c
> @@ -141,6 +141,11 @@ static int __add_cma_heap(struct cma *cma, void *data)
>  {
>  	struct cma_heap *cma_heap;
>  	struct dma_heap_export_info exp_info;
> +	struct cma *default_cma = dev_get_cma_area(NULL);
> +
> +	/* We only add the default heap and explicitly tagged heaps */
> +	if (cma != default_cma && !cma_dma_heap_enabled(cma))
> +		return 0;

Thinking about the pl111 thread[1], I'm wondering if we should also
let drivers call this directly to expose their CMA pools, even if they
aren't tagged for dma-heaps in DT. But perhaps that's too close to
policy.

Cheers,
-Brian

[1] https://lists.freedesktop.org/archives/dri-devel/2020-April/264358.html

>  
>  	cma_heap = kzalloc(sizeof(*cma_heap), GFP_KERNEL);
>  	if (!cma_heap)
> @@ -162,16 +167,11 @@ static int __add_cma_heap(struct cma *cma, void *data)
>  	return 0;
>  }
>  
> -static int add_default_cma_heap(void)
> +static int cma_heaps_init(void)
>  {
> -	struct cma *default_cma = dev_get_cma_area(NULL);
> -	int ret = 0;
> -
> -	if (default_cma)
> -		ret = __add_cma_heap(default_cma, NULL);
> -
> -	return ret;
> +	cma_for_each_area(__add_cma_heap, NULL);
> +	return 0;
>  }
> -module_init(add_default_cma_heap);
> +module_init(cma_heaps_init);
>  MODULE_DESCRIPTION("DMA-BUF CMA Heap");
>  MODULE_LICENSE("GPL v2");
> -- 
> 2.17.1
>