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Date: Mon, 16 Oct 2023 12:59:49 +0100
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Subject: Re: [PATCH 08/12] dma-direct: warn when coherent allocations aren't
 supported
Content-Language: en-GB
To: Christoph Hellwig <hch@lst.de>, Greg Ungerer <gerg@linux-m68k.org>,
 iommu@lists.linux.dev
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
 Palmer Dabbelt <palmer@dabbelt.com>, Conor Dooley <conor@kernel.org>,
 Geert Uytterhoeven <geert+renesas@glider.be>,
 Magnus Damm <magnus.damm@gmail.com>,
 Marek Szyprowski <m.szyprowski@samsung.com>,
 Geert Uytterhoeven <geert@linux-m68k.org>, Wei Fang <wei.fang@nxp.com>,
 Shenwei Wang <shenwei.wang@nxp.com>, Clark Wang <xiaoning.wang@nxp.com>,
 NXP Linux Team <linux-imx@nxp.com>, linux-m68k@lists.linux-m68k.org,
 netdev@vger.kernel.org, linux-riscv@lists.infradead.org,
 linux-renesas-soc@vger.kernel.org, Jim Quinlan <james.quinlan@broadcom.com>
References: <20231016054755.915155-1-hch@lst.de>
 <20231016054755.915155-9-hch@lst.de>
From: Robin Murphy <robin.murphy@arm.com>
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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@arm.com>

> Signed-off-by: Christoph Hellwig <hch@lst.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;
> +		}
>   	}
>   
>   	/*