Deucher, Alexander wrote:
Even the latest driver lacks the PCI IDs of many HDMI HDA devices (aa50/aa58/aa60/aa68/aa80/aa88/aa90/aa98: Cypress/Juniper/Redwood/Cedar/ Cayman+Antilles/Barts/Turks/Caicos).
Alex, are these devices that require disabling snooping?
Sorry what does snooping mean in this context?
Coherent memory accesses, i.e., not setting bit 18 in the stream descriptor control register; the HDA spec says: | Traffic Priority (TP): If set to a 1, the stream will be treated as | preferred traffic if the underlying bus supports it. If set to a 0, | the traffic will be handled on a “best effort” basis. [...] | On PCI Express, for example, setting the TP bit to a 1 might cause | the controller to generate non-snooped isochronous traffic, while | a PCI implementation may ignore this bit. | It is permitted to implement this bit as RO if there is no | controllability available.
So "require" might be wrong, this is just an optimization. Anyway, devices up to aa48 use snooping, while from aaa0 (Tahiti XT) forward, the driver sets TP (http://git.kernel.org/linus/1815b34a6267). The question is, what was the first device to support this?
Regards, Clemens