Hi Greg, > Subject: Re: [PATCH v2 1/3] platform/x86: Add Intel Input Output Manager > (IOM) driver > > On Fri, Aug 28, 2020 at 03:20:22PM +0000, Mani, Rajmohan wrote: > > Hi Greg, > > > > > Subject: Re: [PATCH v2 1/3] platform/x86: Add Intel Input Output > > > Manager > > > (IOM) driver > > > > > > Hi Greg, > > > > > > On Fri, Aug 28, 2020 at 09:43:59AM +0200, Greg Kroah-Hartman wrote: > > > > I still find this crazy that a whole separate driver is created > > > > just to read a single 32bit value. > > > > > > > > Why not put this logic in the driver that wants to read that value? > > > > That would be much simpler, smaller, and more obvious. > > > > > > That would mean that we start maintaining something like DMI quirk > > > table in those drivers. Unfortunately the IOM device is not available on > every platform. > > > Also, even on platforms that do have it, there is no guarantee that > > > the device is always going to be mapped to the same address. > > > > > > Nevertheless, I was originally hoping that we could hide the > > > handling of IOM somehow in ACPI without the need for an actual > > > device object, but it now turns out that the other features of the > > > IOM chip have created interest. At least our i915 guys probable have > > > some use for it (I don't know exactly what they are planning to use it for). > > > > > > So the fact that we may later need the device for something else, on > > > top of the clumsiness and most importantly risks involved with using > > > ACPI to take care of extra tasks (ASL tends to have bugs - bugs that > > > may never ever get fixed), I think the IOM device object, and the > > > driver that binds to it, do have a valid reason for existing. > > > > > > > Intel PMC USB mux device is part of the PCH, while IOM is part of the SoC. > > I have no idea what a "PCH" is, what "IOM" is, and how any of this relates to a > "SoC" :) > I was just meaning to say IOM (Intel Output Manager) is a separate device, that is not part of PCH (Platform Controller Hub) like PMC (Power Management Controller). For the sake of completeness PCH - Platform Controller Hub (usually that handles I/Os in Intel core platforms) IOM - Input Output Manager (IOM) is part of the Tiger Lake SoC that handles Type-C topology, configuration and PM functions of various Type-C devices connected on the platform > Don't impose arbritrary hardware "splits" to kernel code when the kernel has > no such "partitioning" please. > Ack. > > This was another reason we had to have a separate ACPI device. > > That sounds like a firmware issue you can solve in UEFI. > Ack > I think this is the most TLA-laden email I have ever written, and I used to work > at IBM :) I thought it was only Intel where TLAs are abundantly used. Thanks for the reviews and the direction on this topic. > > greg k-h
