On Wed, Aug 26, 2015 at 09:59:13PM +0000, Runyan, Arthur J wrote: > > >From: Ville Syrjälä [mailto:ville.syrjala@xxxxxxxxxxxxxxx] > >> On Wed, Aug 26, 2015 at 04:13:52PM -0300, Paulo Zanoni wrote: > ... > >> Although the doc for LPT _suggests_ this is only for LPT:LP, it > >> doesn't mark this bit as LPT:LP-specific just like it marks all the > >> other LPT:LP-specific bits in every register, so I wonder if this is > >> really LPT:LP or if there's another way to find this out, like some > >> strap or VBT bit. > > > >Hmm. Indeed. There is that note about the enable being in the north > >on DevLPT:H. I guess that's what gave me the idea for this patch. But > >the rest of the text just talks about PCH being on the same package or > >not. Not sure if the two conditions are entirely the same thing. > > > >For HSW the north register says we need this on DevHSW:ULT. For BDW it > >refers us to a package type indication in FUSE_STRAP3, but the only > >relevant looking bit is the ULT mode bit, which it also says is > >currently unused and should be ignored :( > > > >Art, could you help us out here? How should we actually determine > >(on HSW/BDW) whether to enable the DDI A HPD in the north, south, > >or both? > > The north and south hotplug control registers have text to try to explain this in the DDI A HPD enable fields, which I pasted below. You always enable north. You additionally enable south if CPU and PCH are in the same package. OK thanks. That more or less matches my original understanding. > > "This only applies to systems that have the CPU and PCH in the same package, where the DDI A HPD input is connected to the PCH and the HPD must be enabled in both the North Display Engine Registers HOTPLUG_CTL and the South Display Engine Registers SHOTPLUG_CTL. The HPD status is found in North Display Engine Registers HOTPLUG_CTL. > > On systems that have the CPU and PCH in separate packages, the DDI A HPD input is connected to the CPU, and the DDI A HPD input must be enabled in only the North Display Engine Registers HOTPLUG_CTL." > > That fuse may not be correct on all SKUs, but I assume you have other ways to recognize what kind of package it is. I originally listed out ULT and ULX, but it became more complicated with BDW. I'm not aware of any way of identifying the package type. My original assumption was LPT-LP -> MCP, LPT-H -> separate package, and most of the material I've managed to dig up would seem to support that. But it's hard to be sure. -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
