From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH 2/2] ACPI / scan: Parse _CCA and setup device coherency Date: Wed, 29 Apr 2015 18:25:04 +0200 Message-ID: <2968069.n1L1S3Mp2q@wuerfel> References: <1430315049-4663-1-git-send-email-Suravee.Suthikulpanit@amd.com> <1430315049-4663-3-git-send-email-Suravee.Suthikulpanit@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <1430315049-4663-3-git-send-email-Suravee.Suthikulpanit@amd.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-arm-kernel@lists.infradead.org Cc: Suravee Suthikulpanit , rjw@rjwysocki.net, lenb@kernel.org, catalin.marinas@arm.com, will.deacon@arm.com, al.stone@linaro.org, linaro-acpi@lists.linaro.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, leo.duran@amd.com, hanjun.guo@linaro.org, msalter@redhat.com, grant.likely@linaro.org List-Id: linux-acpi@vger.kernel.org On Wednesday 29 April 2015 08:44:09 Suravee Suthikulpanit wrote: > diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c > index 4bf7559..a4db208 100644 > --- a/drivers/acpi/acpi_platform.c > +++ b/drivers/acpi/acpi_platform.c > @@ -108,9 +108,12 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *adev) > if (IS_ERR(pdev)) > dev_err(&adev->dev, "platform device creation failed: %ld\n", > PTR_ERR(pdev)); > - else > + else { > + arch_setup_dma_ops(&pdev->dev, 0, 0, NULL, > + adev->flags.is_coherent); > dev_dbg(&adev->dev, "created platform device %s\n", > dev_name(&pdev->dev)); > + } > > kfree(resources); > Looking at this code in more detail, it seems that it unconditionally sets pdevinfo.dma_mask = DMA_BIT_MASK(32), before calling arch_setup_dma_ops(). This assignment should really done inside of arch_setup_dma_ops() instead, which means we should implement that function on all architectures that support ACPI. For the case where _CCA is missing (or coherency disabled, if you ask me), we would not call that function. On a related note, I'm not sure how to handle different DMA masks here. arch_setup_dma_ops() gets passed a size (and offset) argument, which should match the DMA mask, but I don't know if there is a way to find out the size from ACPI. Should we assume it's always 64-bit DMA capable? For legacy reasons, the default mask is probably best left at 32-bit, but drivers are expected to call dma_set_mask() if they can do 64-bit DMA, and that should fail based on the information provided by the platform if the bus is not capable of doing that. Arnd