From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH] pci: acpi: Generic function for setting up PCI device DMA coherency To: Bjorn Helgaas References: <1439459925-2361-1-git-send-email-Suravee.Suthikulpanit@amd.com> <20150814015004.GA26431@google.com> <55DB6BF6.1030206@amd.com> CC: Rafael Wysocki , Len Brown , "Catalin Marinas" , Will Deacon , "Hanjun Guo" , "linux-acpi@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , linux-arm , Rob Herring , Murali Karicheri , Jeremy Linton From: "Suthikulpanit, Suravee" Message-ID: <55DC4D6D.207@amd.com> Date: Tue, 25 Aug 2015 18:11:41 +0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Sender: linux-acpi-owner@vger.kernel.org List-ID: Hi Bjorn, On 8/25/2015 3:14 AM, Bjorn Helgaas wrote: > On Mon, Aug 24, 2015 at 12:09 PM, Suravee Suthikulpanit > wrote: > >>>> commit 84cfb2213cd400fef227ec0d7829ec4e12895da9 >>>> Author: Bjorn Helgaas >>>> Date: Thu Aug 13 19:49:52 2015 -0500 >>>> >>>> ACPI / scan: Rename acpi_check_dma() to acpi_dma_is_coherent() >>>> >>>> The name "acpi_check_dma()" doesn't give any much indication about >>>> what >>>> exactly it checks. The function also returns information both as a >>>> normal >>>> return value and as the "bool *coherent" return parameter. But >>>> "*coherent" >>>> doesn't actually give any extra information: it is unchanged when >>>> returning >>>> false and set to true when returning true. >>>> >>>> Rename acpi_check_dma() to acpi_dma_is_coherent() so the callers >>>> read more >>>> naturally. Drop the return parameter and just use the function >>>> return >>>> value. >>>> >>>> Signed-off-by: Bjorn Helgaas >> >> >> This was because, at one point, we wanted to be able to differentiate >> between the case _CCA=0 and missing _CCA in ARM64, where we would support >> DMA (using arch-specific cache maintenance) if _CCA=0, and disable DMA when >> missing _CCA on ARM64. >> >> It seems like the logic is now required (please see >> https://www.mail-archive.com/linux-usb@vger.kernel.org/msg62735.html). So, >> we would need the true/false return, and the coherent variable to be able to >> differentiate between the two cases. >> >> Please let me know what you think. > > It's hard for me to comment without seeing the actual patches. I > think returning two values (_CCA-seen and coherent) is a confusing > interface. Ok. Let me simplify this and send out V2. Thanks, Suravee > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >