Re: [PATCH 2/2] ACPI / scan: Refactor _CCA enforcement

From: Bjorn Helgaas <helgaas@kernel.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: hch@lst.de, linux-pci@vger.kernel.org, catalin.marinas@arm.com,
	rjw@rjwysocki.net, linux-kernel@vger.kernel.org,
	will.deacon@arm.com, linux-acpi@vger.kernel.org,
	iommu@lists.linux-foundation.org, gregkh@linuxfoundation.org,
	lenb@kernel.org, linux-arm-kernel@lists.infradead.org,
	m.szyprowski@samsung.com
Subject: Re: [PATCH 2/2] ACPI / scan: Refactor _CCA enforcement
Date: Thu, 20 Dec 2018 09:08:48 -0600	[thread overview]
Message-ID: <20181220150848.GA183878@google.com> (raw)
In-Reply-To: <fe956f04bfe7f8293f6205ee224b087046e40a91.1544199754.git.robin.murphy@arm.com>

On Fri, Dec 07, 2018 at 04:31:35PM +0000, Robin Murphy wrote:
> 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.
> 
> CC: Rafael J. Wysocki <rjw@rjwysocki.net>
> CC: Len Brown <lenb@kernel.org>
> CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> CC: Bjorn Helgaas <bhelgaas@google.com>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

FWIW, if this hasn't been applied already (I think you targeted a DMA
tree):

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

> ---
>  drivers/acpi/scan.c      | 5 +++++
>  drivers/base/platform.c  | 3 +--
>  drivers/pci/pci-driver.c | 3 +--
>  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 41b91af95afb..c6daca875c17 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..f899a28b90f8 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, attr);
>  	}
>  
>  	pci_put_host_bridge_device(bridge);
> -- 
> 2.19.1.dirty
> 
> 
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