linux-kernel - Re: [RFC] m68k: Set up dma mask for platform devices

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Date:   Tue, 15 May 2018 00:10:15 +1000
From:   Greg Ungerer <gerg@...ux-m68k.org>
To:     Finn Thain <fthain@...egraphics.com.au>,
        linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Cc:     Christoph Hellwig <hch@....de>
Subject: Re: [RFC] m68k: Set up dma mask for platform devices

Hi Finn,

On 13/05/18 11:00, Finn Thain wrote:
> This avoids a WARNING splat when loading the macsonic or macmace driver.
> Please see commit 205e1b7f51e4 ("dma-mapping: warn when there is no
> coherent_dma_mask").
> 
> This implementation of arch_setup_pdev_archdata() differs from the one
> in arch/powerpc in that this one avoids clobbering an existing dma mask.
> For example, this approach preserves the mask set by the initializer for
> struct platform_device mcf_fec0.
> 
> Note that either approach would make that initializer redundant and
> commit f61e64310b75 ("m68k: set dma and coherent masks for platform
> FEC ethernets") could be reverted.

Seems reasonable to me. I would be happy to do this and the back out
commit f61e64310b75 ("m68k: set dma and coherent masks for platform
FEC ethernets").

Regards
Greg


> ---
>   arch/m68k/kernel/dma.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/arch/m68k/kernel/dma.c b/arch/m68k/kernel/dma.c
> index c01b9b8f97bf..463572c4943f 100644
> --- a/arch/m68k/kernel/dma.c
> +++ b/arch/m68k/kernel/dma.c
> @@ -9,6 +9,7 @@
>   #include <linux/dma-mapping.h>
>   #include <linux/device.h>
>   #include <linux/kernel.h>
> +#include <linux/platform_device.h>
>   #include <linux/scatterlist.h>
>   #include <linux/slab.h>
>   #include <linux/vmalloc.h>
> @@ -165,3 +166,12 @@ const struct dma_map_ops m68k_dma_ops = {
>   	.sync_sg_for_device	= m68k_dma_sync_sg_for_device,
>   };
>   EXPORT_SYMBOL(m68k_dma_ops);
> +
> +void arch_setup_pdev_archdata(struct platform_device *pdev)
> +{
> +	if (pdev->dev.coherent_dma_mask == DMA_MASK_NONE &&
> +	    pdev->dev.dma_mask == NULL) {
> +		pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
> +		pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
> +	}
> +}
>