On 2/24/21 1:51 AM, Kai Vehmanen wrote:
Hi,
On Tue, 23 Feb 2021, Takashi Iwai wrote:
On Tue, 23 Feb 2021 17:25:23 +0100, Jaroslav Kysela wrote:
A dumb question: Does TGL really support up to 11 separate displays or it's
just to handle 11 connections and the number of maximal simultanenous
connected displays is lower? In the later case, the dynamic allocation makes
That's the latter. And, the fixed assignment was merely for
compatibility with legacy usage, and supposed to be 3 fixed ones or
so. Extending to that high number wasn't intended when the mechanism
was introduced. We should have noticed it at ICL support (which has
up to 6 devices).
yes, exactly. The pins relate to physical ports. There are more pins now
to cater for various DP-over-USB-C topologies (versus just native HDMI and
DP ports). Most product have less physical ports connected, but on the HDA
interface all pins are exposed. Each pin does provide functionality to
query whether a display is connected to it, and whether the connected
display has audio capability.
The maximum number of concurrent displays is described as converters.
On TGL this is 4.
If a physical port supports DP-MST, does the 3 connections on this
physical port share a single converter? And each connection has an
independent pcm, maybe the driver should create pcm pool according to
num_converter * 3.
With SOF, we didn't have legacy userspace, so the HDMI/DP PCMs are already
exposed differently and only a small number (3 or 4) of PCMs are created
depending on hardware generation. Now the question is how we move
snd-hda-intel to similar model with minimal distraction to existing
user-space.
Let's do some change on TGL first, let us see if it will break some
user-space apps, then we could evaluate how to handle it.
Thanks,
Hui.
Br, Kai
