linux-kernel - Re: [PATCH 13/15] ACPI / scan: Refactor

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Date:   Fri, 14 Dec 2018 15:15:33 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Christoph Hellwig <hch@....de>
Cc:     iommu@...ts.linux-foundation.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Toke Høiland-Jørgensen <toke@...e.dk>,
        Robin Murphy <robin.murphy@....com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Keith Busch <keith.busch@...el.com>,
        Jonathan Derrick <jonathan.derrick@...el.com>,
        linux-pci@...r.kernel.org, linux-ia64@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/15] ACPI / scan: Refactor _CCA enforcement

On Fri, Dec 07, 2018 at 11:07:18AM -0800, Christoph Hellwig wrote:
> From: Robin Murphy <robin.murphy@....com>
> 
> Rather than checking the DMA attribute at each callsite, just pass it
> through for acpi_dma_configure() to handle directly. That can then deal
> with the relatively exceptional DEV_DMA_NOT_SUPPORTED case by explicitly
> installing dummy DMA ops instead of just skipping setup entirely. This
> will then free up the dev->dma_ops == NULL case for some valuable
> fastpath optimisations.
> 
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  drivers/acpi/scan.c      | 5 +++++
>  drivers/base/platform.c  | 3 +--
>  drivers/pci/pci-driver.c | 3 +--

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>	# drivers/pci part

>  3 files changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index bd1c59fb0e17..b75ae34ed188 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -1456,6 +1456,11 @@ int acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
>  	const struct iommu_ops *iommu;
>  	u64 dma_addr = 0, size = 0;
>  
> +	if (attr == DEV_DMA_NOT_SUPPORTED) {
> +		set_dma_ops(dev, &dma_dummy_ops);
> +		return 0;
> +	}
> +
>  	iort_dma_setup(dev, &dma_addr, &size);
>  
>  	iommu = iort_iommu_configure(dev);
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index eae841935a45..c1ddf191711e 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -1138,8 +1138,7 @@ int platform_dma_configure(struct device *dev)
>  		ret = of_dma_configure(dev, dev->of_node, true);
>  	} else if (has_acpi_companion(dev)) {
>  		attr = acpi_get_dma_attr(to_acpi_device_node(dev->fwnode));
> -		if (attr != DEV_DMA_NOT_SUPPORTED)
> -			ret = acpi_dma_configure(dev, attr);
> +		ret = acpi_dma_configure(dev, attr);
>  	}
>  
>  	return ret;
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index bef17c3fca67..1b58e058b13f 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -1602,8 +1602,7 @@ static int pci_dma_configure(struct device *dev)
>  		struct acpi_device *adev = to_acpi_device_node(bridge->fwnode);
>  		enum dev_dma_attr attr = acpi_get_dma_attr(adev);
>  
> -		if (attr != DEV_DMA_NOT_SUPPORTED)
> -			ret = acpi_dma_configure(dev, attr);
> +		ret = acpi_dma_configure(dev, acpi_get_dma_attr(adev));
>  	}
>  
>  	pci_put_host_bridge_device(bridge);
> -- 
> 2.19.1
>