On Thu, Jul 02, 2020 at 04:22:00PM +0800, Hanjun Guo wrote: > Hi Robin, > > On 2020/7/2 0:12, Robin Murphy wrote: > > On 2020-06-30 14:04, Hanjun Guo wrote: > > > On 2020/6/30 18:24, Lorenzo Pieralisi wrote: > > > > On Tue, Jun 30, 2020 at 11:06:41AM +0800, Hanjun Guo wrote: > > > > > > > > [...] > > > > > > > > > > For devices that aren't described in the DSDT - IORT translations > > > > > > are determined by their ACPI parent device. Do you see/Have you > > > > > > found any issue with this approach ? > > > > > > > > > > The spec says "Describes the IO relationships between devices > > > > > represented in the ACPI namespace.", and in section 3.1.1.3 Named > > > > > component node, it says: > > > > > > > > PCI devices aren't necessarily described in the ACPI namespace and we > > > > still use IORT to describe them - through the RC node. > > > > > > > > > "Named component nodes are used to describe devices that are also > > > > > included in the Differentiated System Description Table (DSDT). See > > > > > [ACPI]." > > > > > > > > > > So from my understanding, the IORT spec for now, can only do ID > > > > > translations for devices in the DSDT. > > > > > > > > I think you can read this multiple ways but this patch does not > > > > change this concept. What changes, is applying parent's node IORT > > > > mapping to child nodes with no associated DSDT nodes, it is the > > > > same thing we do with PCI and the _DMA method - we could update > > > > the wording in the specs if that clarifies but I don't think this > > > > deliberately disregards the specifications. > > > > > > I agree, but it's better to update the wording of the spec. > > > > > > > > > > > > > > For a platform device, if I use its parent's full path name for > > > > > > > its named component entry, then it will match, but this will violate > > > > > > > the IORT spec. > > > > > > > > > > > > Can you elaborate on this please I don't get the point you > > > > > > are making. > > > > > > > > > > For example, device A is not described in DSDT so can't represent > > > > > as a NC node in IORT. Device B can be described in DSDT and it > > > > > is the parent of device A, so device B can be represented in IORT > > > > > with memory access properties and node flags with Substream width > > > > > and Stall supported info. > > > > > > > > > > When we trying to translate device A's ID, we reuse all the memory > > > > > access properties and node flags from its parent (device B), but > > > > > will it the same? > > > > > > > > I assume so why wouldn't it be ? Why would be describe them in > > > > a parent-child relationship if that's not how the system looks like > > > > in HW ? > > > > > > The point I'm making is that I'm not sure all the memory access and > > > stall properties are the same for the parent and the device itself. > > > > Is that even a valid case though? The principal thing we want to > > accommodate here is when device B *is* the one accessing memory, either > > because it is a bridge with device A sat behind it, or because device A > > is actually just some logical function or subset of physical device B. > > Thanks for the clarify, for CCA attributes, child device should be the > same as its parent and that was written in the ACPI spec, so it's better > to make it clear for other properties in the spec as well. > > > > > If the topology is such that device A is a completely independent device > > with its own path to memory such that it could have different > > properties, I would expect that it *should* be described in DSDT, and I > > can't easily think of a good reason why it wouldn't be. I'm also > > struggling to imagine how it might even have an ID that had to be > > interpreted in the context of device B if it wasn't one of the cases > > above :/ > > > > I don't doubt that people could - or maybe even have - come up with crap > > DSDT bindings that don't represent the hardware sufficiently accurately, > > but I'm not sure that should be IORT's problem... > > As I said in previous email, I'm not against this patch, and seems > have no regressions for platforms that using named component node > such as D05/D06 (I will test it shortly to make sure), but it's better > to update the wording of the spec (even after this patch set is merged). Have you managed to test this series ? Thanks, Lorenzo
