linux-kernel - Re: [PATCH 2/2] ACPI / scan: Refactor

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Message-ID: <CAJZ5v0g=RSXxFWU-Yu0UA2AFV+qNoW7Q6t1S8ecydrTrHJZwXA@mail.gmail.com>
Date:   Tue, 11 Dec 2018 11:15:04 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Christoph Hellwig <hch@....de>,
        "open list:AMD IOMMU (AMD-VI)" <iommu@...ts.linux-foundation.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] ACPI / scan: Refactor _CCA enforcement

On Fri, Dec 7, 2018 at 5:31 PM Robin Murphy <robin.murphy@....com> 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@...ysocki.net>
> CC: Len Brown <lenb@...nel.org>
> CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> CC: Bjorn Helgaas <bhelgaas@...gle.com>
> Signed-off-by: Robin Murphy <robin.murphy@....com>

The changes in this patch are fine by me:

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.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
>