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

[Robin Murphy]

On 20/06/17 14:42, Christoph Hellwig wrote:
> Wouldn't the smal patch below solve the same issue in a simple way?

That assumes that all devices accessing a shared pool will have the same
 dma_pfn_offset as the first one, which cannot strictly be relied upon
(even if it is highly likely in practice).

Robin.

> 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",
>