linux-kernel - Re: [PATCH 6.0 659/862] =?UTF-8?q?ARM/dma-mapp=D1=96ng:=20dont=20override=20->dma=5Fcohe?= =?UTF-8?q?rent=20when=20set=20from=20a=20bus=20notifier?=

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Message-ID: <Y0+/41/qY8DjVn23@shell.armlinux.org.uk>
Date:   Wed, 19 Oct 2022 10:14:11 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Marek Behún <kabel@...nel.org>,
        Christoph Hellwig <hch@....de>, Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 6.0 659/862] =?UTF-8?q?ARM/dma-mapp=D1=96ng:=20dont=20override=20->dma=5Fcohe?= =?UTF-8?q?rent=20when=20set=20from=20a=20bus=20notifier?=

Hi Greg,

I'm seeing:

Subject: [PATCH 6.0 659/862]
        =?UTF-8?q?ARM/dma-mapp=D1=96ng:=20dont=20override=20->dma=5Fcohe?=
        =?UTF-8?q?rent=20when=20set=20from=20a=20bus=20notifier?=

in mutt, and mutt seems to be unable to decode that. Either a mutt
bug or a bug in your scripts or git...

Russell.

On Wed, Oct 19, 2022 at 10:32:26AM +0200, Greg Kroah-Hartman wrote:
> From: Christoph Hellwig <hch@....de>
> 
> [ Upstream commit 49bc8bebae79c8516cb12f91818f3a7907e3ebce ]
> 
> Commit ae626eb97376 ("ARM/dma-mapping: use dma-direct unconditionally")
> caused a regression on the mvebu platform, wherein devices that are
> dma-coherent are marked as dma-noncoherent, because although
> mvebu_hwcc_notifier() after that commit still marks then as coherent,
> the arm_coherent_dma_ops() function, which is called later, overwrites
> this setting, since it is being called from drivers/of/device.c with
> coherency parameter determined by of_dma_is_coherent(), and the
> device-trees do not declare the 'dma-coherent' property.
> 
> Fix this by defaulting never clearing the dma_coherent flag in
> arm_coherent_dma_ops().
> 
> Fixes: ae626eb97376 ("ARM/dma-mapping: use dma-direct unconditionally")
> Reported-by: Marek Behún <kabel@...nel.org>
> Signed-off-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> Tested-by: Marek Behún <kabel@...nel.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  arch/arm/mm/dma-mapping.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 089c9c644cce..bfc7476f1411 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1769,8 +1769,16 @@ static void arm_teardown_iommu_dma_ops(struct device *dev) { }
>  void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
>  			const struct iommu_ops *iommu, bool coherent)
>  {
> -	dev->archdata.dma_coherent = coherent;
> -	dev->dma_coherent = coherent;
> +	/*
> +	 * Due to legacy code that sets the ->dma_coherent flag from a bus
> +	 * notifier we can't just assign coherent to the ->dma_coherent flag
> +	 * here, but instead have to make sure we only set but never clear it
> +	 * for now.
> +	 */
> +	if (coherent) {
> +		dev->archdata.dma_coherent = true;
> +		dev->dma_coherent = true;
> +	}
>  
>  	/*
>  	 * Don't override the dma_ops if they have already been set. Ideally
> -- 
> 2.35.1
> 
> 
> 
> 

-- 
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