netdev - Re: [PATCH 08/12] dma-direct: warn when coherent allocations aren't supported

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Date: Mon, 16 Oct 2023 12:59:49 +0100
From: Robin Murphy <robin.murphy@....com>
To: Christoph Hellwig <hch@....de>, Greg Ungerer <gerg@...ux-m68k.org>,
 iommu@...ts.linux.dev
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Conor Dooley <conor@...nel.org>,
 Geert Uytterhoeven <geert+renesas@...der.be>,
 Magnus Damm <magnus.damm@...il.com>,
 Marek Szyprowski <m.szyprowski@...sung.com>,
 Geert Uytterhoeven <geert@...ux-m68k.org>, Wei Fang <wei.fang@....com>,
 Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>,
 NXP Linux Team <linux-imx@....com>, linux-m68k@...ts.linux-m68k.org,
 netdev@...r.kernel.org, linux-riscv@...ts.infradead.org,
 linux-renesas-soc@...r.kernel.org, Jim Quinlan <james.quinlan@...adcom.com>
Subject: Re: [PATCH 08/12] dma-direct: warn when coherent allocations aren't
 supported

On 16/10/2023 6:47 am, Christoph Hellwig wrote:
> Log a warning once when dma_alloc_coherent fails because the platform
> does not support coherent allocations at all.

Reviewed-by: Robin Murphy <robin.murphy@....com>

> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>   kernel/dma/direct.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 1327d04fa32a25..fddfea3b2fe173 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -240,8 +240,10 @@ void *dma_direct_alloc(struct device *dev, size_t size,
>   		 */
>   		set_uncached = IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED);
>   		remap = IS_ENABLED(CONFIG_DMA_DIRECT_REMAP);
> -		if (!set_uncached && !remap)
> +		if (!set_uncached && !remap) {
> +			pr_warn_once("coherent DMA allocations not supported on this platform.\n");
>   			return NULL;
> +		}
>   	}
>   
>   	/*