linux-kernel - Re: [PATCH 3/7] openrisc: remove the partial DMA_ATTR_NON

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Date:   Sun, 16 Jun 2019 18:17:24 +0900
From:   Stafford Horne <shorne@...il.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Vineet Gupta <vgupta@...opsys.com>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Helge Deller <deller@....de>,
        Vladimir Murzin <vladimir.murzin@....com>,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        openrisc@...ts.librecores.org, linux-parisc@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] openrisc: remove the partial DMA_ATTR_NON_CONSISTENT
 support

On Fri, Jun 14, 2019 at 04:44:27PM +0200, Christoph Hellwig wrote:
> The openrisc DMA code supports DMA_ATTR_NON_CONSISTENT allocations, but
> does not provide a cache_sync operation.  This means any user of it
> will never be able to actually transfer cache ownership and thus cause
> coherency bugs.

The below looks good.  I am always happy to what looks like legacy copy & paste
cruft.

Acked-by: Stafford Horne <shorne@...il.com>

> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  arch/openrisc/kernel/dma.c | 22 +++++++++-------------
>  1 file changed, 9 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/openrisc/kernel/dma.c b/arch/openrisc/kernel/dma.c
> index f79457cb3741..9f25fd0fbb5d 100644
> --- a/arch/openrisc/kernel/dma.c
> +++ b/arch/openrisc/kernel/dma.c
> @@ -98,15 +98,13 @@ arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
>  
>  	va = (unsigned long)page;
>  
> -	if ((attrs & DMA_ATTR_NON_CONSISTENT) == 0) {
> -		/*
> -		 * We need to iterate through the pages, clearing the dcache for
> -		 * them and setting the cache-inhibit bit.
> -		 */
> -		if (walk_page_range(va, va + size, &walk)) {
> -			free_pages_exact(page, size);
> -			return NULL;
> -		}
> +	/*
> +	 * We need to iterate through the pages, clearing the dcache for
> +	 * them and setting the cache-inhibit bit.
> +	 */
> +	if (walk_page_range(va, va + size, &walk)) {
> +		free_pages_exact(page, size);
> +		return NULL;
>  	}
>  
>  	return (void *)va;
> @@ -122,10 +120,8 @@ arch_dma_free(struct device *dev, size_t size, void *vaddr,
>  		.mm = &init_mm
>  	};
>  
> -	if ((attrs & DMA_ATTR_NON_CONSISTENT) == 0) {
> -		/* walk_page_range shouldn't be able to fail here */
> -		WARN_ON(walk_page_range(va, va + size, &walk));
> -	}
> +	/* walk_page_range shouldn't be able to fail here */
> +	WARN_ON(walk_page_range(va, va + size, &walk));
>  
>  	free_pages_exact(vaddr, size);
>  }
> -- 
> 2.20.1
>