Messages in this thread | | | Subject | Re: [PATCH v1 1/2] PCI: ATS: Add function to check ATS page aligned request status. | From | sathyanarayanan kuppuswamy <> | Date | Mon, 11 Feb 2019 11:24:22 -0800 |
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On 2/11/19 11:15 AM, Raj, Ashok wrote: > On Fri, Feb 08, 2019 at 11:49:55PM -0500, Sinan Kaya wrote: >> On 2/8/2019 8:02 PM, sathyanarayanan kuppuswamy wrote: >>>> This means that you should probably have some kind of version check >>>> here. >>> There is no version field in ATS v1.0 spec. Also, If I follow the history >>> log in PCI spec, I think ATS if first added at v1.2. Please correct me if >>> I am wrong. >> v1.2 was incorporated into PCIe spec at that time. However, the ATS spec >> is old and there could be some HW that could claim to be ATS compatible. >> I know AMD GPUs declare ATS capability. > It seems rather odd we have to check for ATS version. > > I always assumed unspecified bits (Reserved) must be 0. We only check > this if ATS is enabled, and this particular bit wasn't given away for another > feature. > > Is it really required to check for ATS version before consuming this? If the version check is required then, it needs to be added before reading "Invalidate Queue Depth" value as well. > > >> See this ECN >> >> https://composter.com.ua/documents/ats_r1.1_26Jan09.pdf >> >> You need to validate the version field from ATS capability header to be >> 1 before reading this register. >> >> See Table 5-1: ATS Extended Capability Header
-- Sathyanarayanan Kuppuswamy Linux kernel developer
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