Re: [PATCH v5 3/7] drivers: dma-coherent: Account dma_pfn_offset when used with device tree

From	Vladimir Murzin <vladimir.murzin@arm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v5 3/7] drivers: dma-coherent: Account dma_pfn_offset when used with device tree
Date	2017-06-22 15:00 +0200
Message-ID	<tV9Si-4Ry-15@gated-at.bofh.it> (permalink)
References	<tKBIe-15d-7@gated-at.bofh.it> <tKCkW-1Ap-29@gated-at.bofh.it> <tUrHB-Q2-47@gated-at.bofh.it>
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On 20/06/17 14:42, Christoph Hellwig wrote:
> Wouldn't the smal patch below solve the same issue in a simple way?
> 
> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
> index 640a7e63c453..e8f8447d705b 100644
> --- a/drivers/base/dma-coherent.c
> +++ b/drivers/base/dma-coherent.c
> @@ -290,9 +290,11 @@ EXPORT_SYMBOL(dma_mmap_from_coherent);
>  static int rmem_dma_device_init(struct reserved_mem *rmem, struct device *dev)
>  {
>  	struct dma_coherent_mem *mem = rmem->priv;
> +	dma_addr_t dev_addr = ((rmem->base >> PAGE_SHIFT) -
> +				dev->dma_pfn_offset) << PAGE_SHIFT;
>  
>  	if (!mem &&
> -	    !dma_init_coherent_memory(rmem->base, rmem->base, rmem->size,
> +	    !dma_init_coherent_memory(rmem->base, dev_addr, rmem->size,
>  				      DMA_MEMORY_MAP | DMA_MEMORY_EXCLUSIVE,
>  				      &mem)) {
>  		pr_err("Reserved memory: failed to init DMA memory pool at %pa, size %ld MiB\n",
> 

Robin has already commented on this - dma_pfn_offset may vary across devices
and reserved memory region may be shared between them.

Cheers
Vladimir

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Re: [PATCH v5 3/7] drivers: dma-coherent: Account dma_pfn_offset  when used with device tree Christoph Hellwig <hch@infradead.org> - 2017-06-20 15:50 +0200
  Re: [PATCH v5 3/7] drivers: dma-coherent: Account dma_pfn_offset when  used with device tree Robin Murphy <robin.murphy@arm.com> - 2017-06-20 16:00 +0200
    Re: [PATCH v5 3/7] drivers: dma-coherent: Account dma_pfn_offset  when used with device tree Christoph Hellwig <hch@infradead.org> - 2017-06-26 11:40 +0200
  Re: [PATCH v5 3/7] drivers: dma-coherent: Account dma_pfn_offset when  used with device tree Vladimir Murzin <vladimir.murzin@arm.com> - 2017-06-22 15:00 +0200

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