linux-kernel - Re: [PATCH] dma-coherent: fix rmem_dma_device

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Date:   Sun, 17 Sep 2017 12:35:00 +0000
From:   Roy Pledge <roy.pledge@....com>
To:     Arnd Bergmann <arnd@...db.de>, Christoph Hellwig <hch@....de>,
        "Marek Szyprowski" <m.szyprowski@...sung.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Robin Murphy <robin.murphy@....com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        "George G. Davis" <george_davis@...tor.com>,
        "Mark Craske" <Mark_Craske@...tor.com>,
        Bastian Hecht <bhecht@...adit-jv.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dma-coherent: fix rmem_dma_device_init regression

On 9/15/2017 11:08 AM, Arnd Bergmann wrote:
> My recent bug fix introduced another bug, which caused rmem_dma_device_init
> to always fail, as rmem->priv is never set to anything.
> 
> This restores the previous behavior, calling dma_init_coherent_memory()
> whenever ->priv is NULL.
> 
> Fixes: d35b0996fef3 ("dma-coherent: fix dma_declare_coherent_memory() logic error")
> Reported-by: Roy Pledge <roy.pledge@....com>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> Roy, can you test this new fix?
> ---
>   drivers/base/dma-coherent.c | 19 +++++++++----------
>   1 file changed, 9 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
> index a39b2166b145..744f64f43454 100644
> --- a/drivers/base/dma-coherent.c
> +++ b/drivers/base/dma-coherent.c
> @@ -348,16 +348,15 @@ static int rmem_dma_device_init(struct reserved_mem *rmem, struct device *dev)
>   	struct dma_coherent_mem *mem = rmem->priv;
>   	int ret;
>   
> -	if (!mem)
> -		return -ENODEV;
> -
> -	ret = dma_init_coherent_memory(rmem->base, rmem->base, rmem->size,
> -				       DMA_MEMORY_EXCLUSIVE, &mem);
> -
> -	if (ret) {
> -		pr_err("Reserved memory: failed to init DMA memory pool at %pa, size %ld MiB\n",
> -			&rmem->base, (unsigned long)rmem->size / SZ_1M);
> -		return ret;
> +	if (!mem) {
> +		ret = dma_init_coherent_memory(rmem->base, rmem->base,
> +					       rmem->size,
> +					       DMA_MEMORY_EXCLUSIVE, &mem);
> +		if (ret) {
> +			pr_err("Reserved memory: failed to init DMA memory pool at %pa, size %ld MiB\n",
> +				&rmem->base, (unsigned long)rmem->size / SZ_1M);
> +			return ret;
> +		}
>   	}
>   	mem->use_dev_dma_pfn_offset = true;
>   	rmem->priv = mem;
> 
I tried this and it solves the issue I was seeing. Thanks for the quick fix.

Tested-by:  Roy Pledge <roy.pledge@....com>